Дисертації з теми "Elevated fire"

Behaviour under fire circumstances is becoming more and more crucial for designing a concrete structureand authorities require more often a fire-resistance time. In fact, engineers need a powerful, user-friendly,accurate and non time-consuming method that can be used to design reinforced concrete structures. Inthis study, the author has developed a method to design any fire-exposed reinforced concrete crosssections under flexure that takes into account second order effect. The first part focuses on the thermal analysis of the reinforced concrete cross section. Fourier'sequation is solved using finite differences method and the development tool of Excel: Virtual BasicAdvanced macro. Thus, it could easily be used on every personal computer (reasonably powerful) andneeds no extra investment. The accuracy of this thermal analysis is checked by comparison with resultsfrom commercial softwares (FAGUS edited by Cubus and SAFIR developed by the university of Liege). The second part deals with the mechanical analysis. Indeed, the concrete compressive strengthtogether with the yield strength of the steel reinforcement bars will decrease when the temperature willraise inside the concrete cross section. This loss of characteristic will be regarded as a loss of area andnew dimensions are set up. Finally a classic analysis (as it can be done at ambient temperature) isperformed. The mechanical analysis which takes into account second order effect is based on the Eulerbuckling load. The last chapter presents a comparison study between this new method and the two commercialsoftwares FAGUS and SAFIR, both of them are using finite element method. Several cross sections havebeen modelled, T-shaped ones with various dimensions and rectangular ones with various dimensionsand various steel areas. The two aspects (mechanical and thermal) have been studied and the resultsshowed good correspondance.
Master thesis

In general, it is expected that concrete structures using Glass Fibre Reinforced Plastic (GFRP) rebars as reinforcement could have improved durability compared to normal steel reinforcement because of the corrosion resistance of the rebar. However, there are some aspects of the behaviour of the GFRP bars under high temperature that must be explored. The aims of this work are to predict the fire rating of the GFRP rebars when embedded in concrete elements by creating a model and to validate the model by full-scale experiments. The first part of this work evaluates the effects of alkaline environments on the rebar itself, the bond strength at interface between the concrete and the rebar, and the strength of the GFRP rebars at a range of different temperatures (20-120°C). The three types of GFRP rods investigated in this work were subjected to alkaline solutions at 60°C for three different exposure times i. e. 30 days, 120 days and 240 days. Tensile and flexural tests were carried out for the physico-mechanical characterisation on the treated GFRP rebars specimens. As the immersion period and temperature increased, the strength of the rebars decreased. Data obtained from the first part of the work were used to predict long-term performance of the GFRP rebar in fire. The effects of higher temperatures with time on GFRP reinforced concrete members were also studied experimentally in this work. As a result equations were developed. These were validated with the help of the fire tests carried out in second phase of this work on two full-scale GFRP reinforced concrete beams. The first beam was reinforced with GFRP made from thermoset resin and in the second GFRP made from thermoplastic resin was used. Shear reinforcement for the first beam were GFRP stirrups and for the second beam steel stirrups were used. Degradation of flexural and shear capacities due to fire was evaluated using the modified design codes which is based on assessment of the reduction in the initial strengths of concrete and GFRP reinforcement, resulting from the high temperatures developed inside the beam. A comparison of the results for each beam is presented. Fire resistance (load bearing capacity) of GFRP RC beams complied with British Standard BS 478. These results are published for the first time in this work. The predicted failure time using the model compares well with the fire test results. The 3 result also indicated that the basic fire model needed adjustment mainly due to a difference in the assumed and observed failure modes. The importance of data necessary for a more accurate model has been identified as a programme for future work.

Exposure of concrete structures to high temperatures leads to significant losses in mechanical and physical properties of concrete and steel reinforcement as well as the bond characteristics between them. Degradation of bond properties in fire may significantly influence the load capacity of concrete structures. Therefore the bond behaviours need to be considered for the structural fire engineering design of reinforced concrete structures. At present, the information about the material degradations of concrete and reinforcing steel bars at elevated temperatures are generally available. However, the research on the response of the bond characteristic between concrete and reinforcing steel bar at elevated temperatures is still limited. Due to the lack of robust models for considering the influence of the bond characteristics between the concrete and steel bar at elevated temperatures, the majority of the numerical models developed for predicting the behaviour of reinforced concrete structures in fire was based on the full bond interaction. Hence, the main purpose of this research is to develop robust numerical models for predicting the bond-slip between concrete and the reinforcement under fire conditions. Therefore, the bond-slip between the concrete and reinforcement for conventional and prestress concrete structures at both ambient and elevated temperatures has been investigated in this research. Two models have been developed in this study: the first model is to simulate the behaviour of bond-slip of deformed steel bars in normal concrete at room temperature and under fire conditions. The model is established based on a partly cracked thick-wall cylinder theory and the smeared cracking approach is adopted to consider the softening behaviour of concrete in tension. The model is able to consider a number of parameters: such as different concrete properties and covers, different steel bar diameters and geometries. The proposed model has been incorporated into the Vulcan program for 3D analysis of reinforced concrete structures in fire. The second robust model has been developed to predict the bond stress-slip relationship between the strand and concrete of prestressed concrete structural members. In this model, two bond-slip curves have been proposed to represent the bond-slip characteristics for the three-wire and seven-wire strands. This model considers the variation of concrete properties, strands’ geometries and the type of strand surface (smooth or indented). The degradation of materials and bond characteristic at elevated temperatures are also included in the model. The proposed models have been validated against previous experimental results at both ambient and elevated temperatures and good agreements have been achieved. A comprehensive parametric study has been carried out in this research to examine the influence of bond-slip model on the structural behaviours of normal reinforced concrete structures. The study investigated the most important factors that can affect the bond characteristics between concrete and steel reinforcement at elevated temperatures. These factors are: the concrete cover, spalling of concrete, concrete compressive and tensile strengths.

The variation in the compressive strength of concrete block masonry was studied at elevated temperatures. Small specimens known as wallettes were used to obtain the compressive strength under steady state conditions. Eighteen wallettes were made of lightweight concrete blocks and 1:1:5 mortar proportion. The target temperatures were 20°C, 200°C, 400°C, 600°C, 700°C and 800°C. Initially load-deflection relationships were determined from the experimental wallettes and later they were converted into stress-strain relationships. Although the goal was to determine the compressive strength, other parameters were also studied such as modulus of elasticity, temperature-time relationships, modes of failure, material degradation, and change of colour.Lightweight concrete blocks were also tested to determine the compressive strength at equal temperatures applied for the wallettes. The blocks belonged to the same batch used for the wallettes. The tensile behaviour of mortar was determined at 20°C, 200°C and 400°C.Once the mechanical properties of the masonry wallettes, units and mortar were determined, they were used as input data to develop finite element models to simulate the same behaviour of the experimental wallettes. Finally, using the experimental and numerical results from the wallettes, they were used to predict the behaviour of 3m height walls.

The structural behaviour of single shear bolted connections and double shear bolted connections of cold-formed stainless steel at elevated temperatures and post-fire condition has been investigated in this study. The current design rules on bolted connections of cold-formed stainless steel are mainly based on those of carbon steel, and are applicable for room (ambient) temperature condition only. These design rules may not be applicable for elevated temperatures. Therefore, design guidelines should be prepared for bolted connections of cold-formed stainless steel structures at elevated temperatures. The key findings of the investigation are described in the following paragraphs. A total of 25 tensile coupon tests were conducted to investigate the material deterioration of three different grades of stainless steel at elevated temperatures. The stainless steels are austenitic stainless steel EN 1.4301 (AISI 304) and EN 1.4571 (AISI 316Ti having small amount of titanium) as well as lean duplex stainless steel EN 1.4162 (AISI S32101). Totally 434 tests on bolted connections of stainless steel were performed in the temperature ranged from 22 to 950 ºC using both steady state and transient state test methods. The test results were compared with the nominal strengths calculated from the American Specification, Australian/New Zealand Standard and European codes for stainless steel structures. In calculating the nominal strengths of the connections, the material properties at elevated temperatures were used in the design equations for room temperature. It is shown that the nominal strengths predicted by these specifications are generally conservative at elevated temperatures. A total of 78 cold-formed stainless steel single shear and double shear bolted connections were tested in post-fire condition. The test results were compared with those tested at room temperature. Generally, it is found that the bolted connection strengths in post-fire condition cooling down from 350 and 650 ºC are higher than those tested at room temperature for all three grades of stainless steel. Finite element models for single shear and double shear bolted connections were developed and verified against the experimental results. Static analysis technique was used in the numerical analyses. Extensive parametric studies that included 450 specimens were performed using the verified finite element models to evaluate the bearing resistances of bolted connections of stainless steel at elevated temperatures. Design equations for bearing resistances of cold-formed stainless steel single shear and double shear bolted connections were proposed based on both the experimental and numerical results in the temperature ranged from 22 to 950 ºC. The bearing resistances of bolted connections obtained from the tests and the finite element analyses were compared with the nominal strengths calculated using the current design rules and also compared with the predicted strengths calculated using the proposed design equations. It is shown that the proposed design equations are generally more accurate and reliable in predicting the bearing resistances of bolted connections at elevated temperatures than the current design rules. The reliability of the current and proposed design rules was evaluated using reliability analysis. The proposed design equations are recommended for bolted connections assembled using cold-formed stainless steels.
published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy

Intumescent coating fire protection on steel structures is becoming widely popular in the UK and Europe. The current assessment for the fire protection performance method using the standard fire resistance tests is not accurate, owing to the reactive behaviour of intumescent coating at elevated temperature. Moreover, the available intumescent coating temperature assessment method provided in the Eurocode for structural steel at elevated temperature does not incorporate the steel beam's behaviour and/or assessment for partial protection and/or damaged protection. The research work presented provides additional information. on the assessment of partial and/or damaged intumescent coating at elevated temperature. In the scope of the investigation on the thermal conductivity of intumescent coating, it was found that the computed average thermal conductivity was marginally sensitive to the density and emissivity at elevated temperature. However, the thermal conductivity was found to be reasonably sensitive to the differences in initial dft's (dry film thicknesses). In this research, a numerical model was developed using ABAQUS to mimic actual indicative test scenarios to predict and establish the temperature distribution and the structural fire resistance of partial and/or damaged intumescent coating at elevated temperatures. Intumescent coating actively shields when the charring process occurs when the surface temperature reaches approximately 250°C to 350°C. Maximum deflection and deflection failure times for each damage scenario were analyzed by applying specified loading conditions. It was also found that the structural fire resistance failure mode of intumescent coating on protected steel beams was particularly sensitive to the applied boundary conditions. Careful selection of nodes in the element was necessary to avoid numerical instability and unexpected numerical error during analysis. An assessment of various numerical models subjected to a-standard fire with partially protected 1 mm intumescent coating was analysed using ABAQUS. An available unprotected test result was used as a benchmark. The outcome suggests that the fire resistances of the beams were found to be sensitive to the location of the partial and/or damage protection. The overall fire resistance behaviour of intumescent coating at elevated temperature was summarized in a 'typical deflection regression' curve. An extensive parametric analysis was performed on localized intumescent coating damage with various intumescent coating thicknesses between 0.5mm to 2.0mm. It was found that the average deflection was linear for the first 30 mins of exposure for all the variables, damage locations and intumescent thicknesses. It was concluded that a thicker layered intumescent coating may not be a better insulator or be compared to a much less thick intumescent coating at elevated temperature. The use of passive fire protection, however, does enhance the overall fire resistance of the steel beam, in contrast to a naked steel structure. The research work investigated the intumescent coating behaviour with different aspects of protection and damage and the outcome of the assessment provided a robust guide and additional understanding of the performance of intumescent coating at elevated temperature.

This thesis presents the results of a research programme to investigate the behaviour and robustness of reinforced concrete (RC) frames in fire. The research was carried out through numerical simulations using the commercial finite element analysis package TNO DIANA. The main focus of the project is the large deflection behaviour of restrained reinforced concrete beams, in particular the development of catenary action, because this behaviour is the most important factor that influences the frame response under accidental loading. This research includes four main parts as follows: (1) validation of the simulation model; (2) behaviour of axially and rotationally restrained RC beams at elevated temperatures; (3) derivation of an analytical method to estimate the key quantities of restrained RC beam behaviour at elevated temperatures; (4) response and robustness of RC frame structures with different extents of damage at elevated temperatures. The analytical method has been developed to estimate the following three quantities: when the axial compression force in the restrained beam reaches the maximum; when the RC beams reach bending limits (axial force = 0) and when the beams finally fail. To estimate the time to failure, which is initiated by the fracture of reinforcement steel at the catenary action stage, a regression equation is proposed to calculate the maximum deflections of RC beams, based on an analysis of the reinforcement steel strain distributions at failure for a large number of parametric study results. A comparison between the analytical and simulation results indicates that the analytical method gives reasonably good approximations to the numerical simulation results. Based on the frame simulation results, it has been found that if a member is completely removed from the structure, the structure is unlikely to be able to develop an alternative load carrying mechanism to ensure robustness of the structure. This problem is particularly severe when a corner column is removed. However, it is possible for frames with partially damaged columns to achieve the required robustness in fire, provided the columns still have sufficient resistance to allow the beams to develop some catenary action. This may be possible if the columns are designed as simply supported columns, but have some reserves of strength in the frame due to continuity. Merely increasing the reinforcement steel area or ductility (which is difficult to do) would not be sufficient. However, increasing the cover thickness of the reinforcement steel to slow down the temperature increase is necessary.

This thesis presents the results of a research project to develop methods to carry out fire safety design of welded steel tubular trusses at elevated temperatures due to fire exposure. It deals with three subjects: resistance of welded tubular joints at elevated temperatures, effects of large truss deflection in fire on member design and effects of localised heating. The objectives of the project are achieved through numerical finite element modelling at elevated temperatures using the commercial Finite Element software ABAQUS v6.10-1 (2011). Validation of the simulation model for joints is based on comparison against the test results of Nguyen et al. (2010) and Kurobane et al. (1986). Validation of the simulation model for trusses is through checking against the test results of Edwards (2004) and Liu et al. (2010).For welded tubular joints, extensive numerical simulations have been conducted on T-, Y-, X-, N- and non-overlapped K-joints subjected to brace axial compression or tension, considering a wide range of geometrical parameters. Uniform temperature distribution was assumed for both the chord and brace members. Results of the numerical simulations indicate for gap K- and N-joints (two brace members, one in tension and the other in compression) and for T-, Y- and X-joints with the brace member under axial tensile load (one brace member only, in tension), it is suitable to use the same ambient temperature calculation equation as in the CIDECT (2010) or EN 1993-1-8 (CEN, 2005a) design guides and simply replace the ambient temperature strength of steel with the elevated temperature value. However, for T-, Y- and X-joints under brace compression load (one brace member only, in compression), the effect of large chord deformation should be considered. Large chord deformation changes the chord geometry and invalidates the assumed yield line mechanism at ambient temperature. For approximation, the results of this research indicate that it is acceptable to modify the ambient temperature joint strength by a reduction factor for the elastic modulus of steel at elevated temperatures. In the current fire safety design method for steel truss, a member based approach is used. In this approach, the truss member forces are calculated at ambient temperature based on linear elastic analysis. These forces are then used to calculate the truss member limiting temperatures. An extensive parametric study has been carried out to investigate whether this method is appropriate. The parametric study encompasses different design parameters over a wide range of values, including truss type, joint type, truss span-to-depth ratio, critical member slenderness, applied load ratio, number of brace members, initial imperfection and thermal elongation. The results of this research show that due to a truss undergoing large displacements at elevated temperatures, some truss members (compression brace members near the truss centre) experience large increases in member forces. Therefore, using the ambient temperature member force, as in the current truss fire safety design method, may overestimate the truss member critical temperature by 100 °C. A method has been proposed to analytically calculate the increase in brace compressive force due to large truss deformation. In this method, the maximum truss displacement is assumed to be span/30. A comparison of the results calculated using the proposed method against the truss parametric study results has shown good agreement with the two sets of results, with the calculation results generally being slightly on the safe side. When different members of a truss are heated to different temperatures due to localised fire exposure, the brace members in compression experience increased compression due to restrained thermal expansion. To calculate the critical temperature of a brace member in a localised heated truss, it is necessary to consider this effect of restrained thermal expansion. It is also necessary to consider the beneficial effects of the adjacent members being heated, which tends to reduce the increase in compressive force in the critical member under consideration. Again, an extensive set of parametric studies have been conducted, for different load ratio, slenderness and axial restraint ratio. The results of this parametric study suggest that to calculate the critical temperature of a brace member, it is not necessary to consider the effects of the third or further adjacent members being heated. For the remainder of the heated members, this thesis has proposed a linear elastic, static analysis method at ambient temperature to calculate the additional compressive force (some negative, indicating tension) in the critical member caused by the heated members (including the critical member itself and the adjacent members). The additional compressive force is then used to calculate the limiting temperature of the critical member. For this purpose, the approximate analytical equation of Wang et al. (2010) has been demonstrated to be suitable.

This thesis presented a comprehensive study on the fire performance of load-bearing high-strength and cold-formed steel hollow section columns using experimental and numerical investigations. Accurate design tools have been developed to predict the ambient and elevated temperature structural capacities and fire resistance ratings of these columns. These developed design methods can be used to decide where bare steel columns can be used, and to design any required fire protection. Overall this research has significantly improved the knowledge and understanding of the structural fire performance of cold-formed steel hollow section columns, and thus enabling considerable improvements to the fire safety of steel buildings.

In recent times, light gauge cold-formed steel sections have been used extensively in residential, industrial and commercial buildings as primary load bearing structural components. This is because cold-formed steel sections have a very high strength to weight ratio compared with thicker hot-rolled steel sections, and their manufacturing process is simple and cost-effective. However, these members are susceptible to various buckling modes including local and distortional buckling and their ultimate strength behaviour is governed by these buckling modes. Fire safety design of building structures has received greater attention in recent times due to continuing loss of properties and lives during fires. Hence, there is a need to fully evaluate the performance of light gauge cold-formed steel structures under fire conditions. Past fire research has focused heavily on heavier, hot-rolled steel members. The buckling behaviour of light gauge cold-formed steel members under fire conditions is not well understood. The buckling effects associated with thin steels are significant and have to be taken into account in fire safety design. Therefore, a research project based on extensive experimental and numerical studies was undertaken at the Queensland University of Technology to investigate the distortional buckling behaviour of light gauge cold-formed steel compression members under simulated fire conditions. As the first phase of this research program more than 115 tensile coupon tests of light gauge cold-formed steels including two steel grades and five thicknesses were conducted at elevated temperatures. Accurate mechanical properties including the yield strength, elasticity modulus and stress-strain curves were all determined at elevated temperatures since the deterioration of the mechanical properties is one of the major parameters in the structural design under fire conditions. An appropriate stress-strain model was also developed by considering the inelastic characteristics. The results obtained from the tensile coupon tests were then used to predict the ultimate strength of cold-formed steel compression members. In the second phase of this research more than 170 laboratory experiments were undertaken to investigate the distortional buckling behaviour of light gauge coldformed steel compression members at ambient and elevated temperatures. Two types of cross sections were selected with various thicknesses (nominal thicknesses are 0.6, 0.8, and 0.95 mm) and both low and high strength steels (G250 and G550 steels with minimum yield strengths of 250 and 550 MPa). The experiments were conducted at six different temperatures in the range of 20 to 800°C. A finite element model of the tested compression members was then developed and validated with the help of experimental results. The degradation of mechanical properties with increasing temperatures was included in finite element analyses. An extensive series of parametric analyses was undertaken using the validated finite element model to investigate the effect of all the influential parameters such as section geometry, steel thickness and grade, mechanical properties and temperature. The resulting large data base of ultimate loads of compression members subject to distortional buckling was then used to review the adequacy of the current design rules at ambient temperature. The current design rules were reasonably accurate in general, but in order to improve the accuracy further, this research has developed new design equations to determine the ultimate loads of compression members at ambient temperature. The developed equation was then simply modified by including the relevant mechanical properties at elevated temperatures. It was found that this simple modification based on reduced mechanical properties gave reasonable results, but not at higher temperatures. Therefore, they were further modified to obtain a more accurate design equation at elevated temperatures. The accuracy of new design rules was then verified by comparing their predictions with the results obtained from the parametric study. This thesis presents a description of the experimental and numerical studies undertaken in this research and the results including comparison with simply modified current design rules. It describes the laboratory experiments at ambient and elevated temperatures. It also describes the finite element models of cold-formed steel compression members developed in this research that included the appropriate mechanical properties, initial geometric imperfections and residual stresses. Finally, it presents the details of the new design equations proposed for the light gauge coldformed steel compression members subjected to distortional buckling effects at elevated temperatures.

In recent times, light gauge cold-formed steel sections have been used extensively in residential, industrial and commercial buildings as primary load bearing structural components. This is because cold-formed steel sections have a very high strength to weight ratio compared with thicker hot-rolled steel sections, and their manufacturing process is simple and cost-effective. However, these members are susceptible to various buckling modes including local and distortional buckling and their ultimate strength behaviour is governed by these buckling modes. Fire safety design of building structures has received greater attention in recent times due to continuing loss of properties and lives during fires. Hence, there is a need to fully evaluate the performance of light gauge cold-formed steel structures under fire conditions. Past fire research has focused heavily on heavier, hot-rolled steel members. The buckling behaviour of light gauge cold-formed steel members under fire conditions is not well understood. The buckling effects associated with thin steels are significant and have to be taken into account in fire safety design. Therefore, a research project based on extensive experimental and numerical studies was undertaken at the Queensland University of Technology to investigate the distortional buckling behaviour of light gauge cold-formed steel compression members under simulated fire conditions. As the first phase of this research program more than 115 tensile coupon tests of light gauge cold-formed steels including two steel grades and five thicknesses were conducted at elevated temperatures. Accurate mechanical properties including the yield strength, elasticity modulus and stress-strain curves were all determined at elevated temperatures since the deterioration of the mechanical properties is one of the major parameters in the structural design under fire conditions. An appropriate stress-strain model was also developed by considering the inelastic characteristics. The results obtained from the tensile coupon tests were then used to predict the ultimate strength of cold-formed steel compression members. In the second phase of this research more than 170 laboratory experiments were undertaken to investigate the distortional buckling behaviour of light gauge coldformed steel compression members at ambient and elevated temperatures. Two types of cross sections were selected with various thicknesses (nominal thicknesses are 0.6, 0.8, and 0.95 mm) and both low and high strength steels (G250 and G550 steels with minimum yield strengths of 250 and 550 MPa). The experiments were conducted at six different temperatures in the range of 20 to 800°C. A finite element model of the tested compression members was then developed and validated with the help of experimental results. The degradation of mechanical properties with increasing temperatures was included in finite element analyses. An extensive series of parametric analyses was undertaken using the validated finite element model to investigate the effect of all the influential parameters such as section geometry, steel thickness and grade, mechanical properties and temperature. The resulting large data base of ultimate loads of compression members subject to distortional buckling was then used to review the adequacy of the current design rules at ambient temperature. The current design rules were reasonably accurate in general, but in order to improve the accuracy further, this research has developed new design equations to determine the ultimate loads of compression members at ambient temperature. The developed equation was then simply modified by including the relevant mechanical properties at elevated temperatures. It was found that this simple modification based on reduced mechanical properties gave reasonable results, but not at higher temperatures. Therefore, they were further modified to obtain a more accurate design equation at elevated temperatures. The accuracy of new design rules was then verified by comparing their predictions with the results obtained from the parametric study. This thesis presents a description of the experimental and numerical studies undertaken in this research and the results including comparison with simply modified current design rules. It describes the laboratory experiments at ambient and elevated temperatures. It also describes the finite element models of cold-formed steel compression members developed in this research that included the appropriate mechanical properties, initial geometric imperfections and residual stresses. Finally, it presents the details of the new design equations proposed for the light gauge coldformed steel compression members subjected to distortional buckling effects at elevated temperatures.

Steel beams with web openings are frequently used in construction to achieve attractive, flexible and optimised design solutions. These beams are used to provide passages for building services, to reduce the overall construction height and to achieve long spans. However, the presence of the openings may lead to a substantial reduction in the load carrying capacity of the beam at both ambient and elevated temperatures and introduce additional failure modes including shear-moment interaction at the location of the openings causing the Vierendeel mechanism. Steel beams in practical construction are axially restrained and the presence of this axial restraint can drastically change the behaviour of the beams in comparison to those without axial restraint. One particular issue is premature buckling of the compressive tee-sections around the openings. The aim of this research is to investigate the effects of openings on axially restrained steel beams at elevated temperatures so as to develop an analytical method for design consideration. The analytical derivation will be based on the results of extensive numerical simulations. The research starts with the behaviour of steel beams with web openings under combined axial compression, bending moment and shear force at ambient temperature. The results show that buckling of the compressive tee-sections at the openings can reduce the plastic moment capacity of the openings; and an analytical method has been proposed to incorporate the influences of axial compression and tee-section buckling into the existing shear-moment design equations. The elevated temperature simulations show that axially restrained steel beams with web openings may enter catenary action at much lower temperatures than the commonly accepted critical failure temperatures calculated assuming no axial restraint and no tee-section buckling. Therefore, at the commonly accepted critical failure temperatures, many perforated steel beams exert tensile forces on the adjacent connections. It is important that the connections have the strength and deformation (rotation) capacity to enable catenary action to develop. The parametric study examines, in detail, how changing the different design parameters may affect the elevated temperature behaviour of perforated beams. The examined parameters including load ratio, level of axial restraint, cross-section temperature distribution profile, opening shape, opening size and opening position. Based on the results of the numerical parametric study, an analytical method has been derived to obtain the complete axial force-temperature relationship for axially restrained perforated steel beams. The key points of the analytical method include initial stiffness, point of initial failure under combined axial compression, bending moment and shear force, transition temperature at which the axial force on the beam changes from compression to tension and the magnitude of the tensile force resulting from the beams going into catenary action. Using the analytical method, it is possible to assess the maximum tensile force in the beam and the corresponding temperature so that the safety of the connections can be checked.

Cold-formed steel members have been widely used in residential, industrial and commercial buildings as primary load bearing structural elements and non-load bearing structural elements (partitions) due to their advantages such as higher strength to weight ratio over the other structural materials such as hot-rolled steel, timber and concrete. Cold-formed steel members are often made from thin steel sheets and hence they are more susceptible to various buckling modes. Generally short columns are susceptible to local or distortional buckling while long columns to flexural or flexural-torsional buckling. Fire safety design of building structures is an essential requirement as fire events can cause loss of property and lives. Therefore it is essential to understand the fire performance of light gauge cold-formed steel structures under fire conditions. The buckling behaviour of cold-formed steel compression members under fire conditions is not well investigated yet and hence there is a lack of knowledge on the fire performance of cold-formed steel compression members. Current cold-formed steel design standards do not provide adequate design guidelines for the fire design of cold-formed steel compression members. Therefore a research project based on extensive experimental and numerical studies was undertaken at the Queensland University of Technology to investigate the buckling behaviour of light gauge cold-formed steel compression members under simulated fire conditions. As the first phase of this research, a detailed review was undertaken on the mechanical properties of light gauge cold-formed steels at elevated temperatures and the most reliable predictive models for mechanical properties and stress-strain models based on detailed experimental investigations were identified. Their accuracy was verified experimentally by carrying out a series of tensile coupon tests at ambient and elevated temperatures. As the second phase of this research, local buckling behaviour was investigated based on the experimental and numerical investigations at ambient and elevated temperatures. First a series of 91 local buckling tests was carried out at ambient and elevated temperatures on lipped and unlipped channels made of G250-0.95, G550-0.95, G250-1.95 and G450-1.90 cold-formed steels. Suitable finite element models were then developed to simulate the experimental conditions. These models were converted to ideal finite element models to undertake detailed parametric study. Finally all the ultimate load capacity results for local buckling were compared with the available design methods based on AS/NZS 4600, BS 5950 Part 5, Eurocode 3 Part 1.2 and the direct strength method (DSM), and suitable recommendations were made for the fire design of cold-formed steel compression members subject to local buckling. As the third phase of this research, flexural-torsional buckling behaviour was investigated experimentally and numerically. Two series of 39 flexural-torsional buckling tests were undertaken at ambient and elevated temperatures. The first series consisted 2800 mm long columns of G550-0.95, G250-1.95 and G450-1.90 cold-formed steel lipped channel columns while the second series contained 1800 mm long lipped channel columns of the same steel thickness and strength grades. All the experimental tests were simulated using a suitable finite element model, and the same model was used in a detailed parametric study following validation. Based on the comparison of results from the experimental and parametric studies with the available design methods, suitable design recommendations were made. This thesis presents a detailed description of the experimental and numerical studies undertaken on the mechanical properties and the local and flexural-torsional bucking behaviour of cold-formed steel compression member at ambient and elevated temperatures. It also describes the currently available ambient temperature design methods and their accuracy when used for fire design with appropriately reduced mechanical properties at elevated temperatures. Available fire design methods are also included and their accuracy in predicting the ultimate load capacity at elevated temperatures was investigated. This research has shown that the current ambient temperature design methods are capable of predicting the local and flexural-torsional buckling capacities of cold-formed steel compression members at elevated temperatures with the use of reduced mechanical properties. However, the elevated temperature design method in Eurocode 3 Part 1.2 is overly conservative and hence unsuitable, particularly in the case of flexural-torsional buckling at elevated temperatures.

Cold-formed steel members have been widely used in residential, industrial and commercial buildings as primary load bearing structural elements and non-load bearing structural elements (partitions) due to their advantages such as higher strength to weight ratio over the other structural materials such as hot-rolled steel, timber and concrete. Cold-formed steel members are often made from thin steel sheets and hence they are more susceptible to various buckling modes. Generally short columns are susceptible to local or distortional buckling while long columns to flexural or flexural-torsional buckling. Fire safety design of building structures is an essential requirement as fire events can cause loss of property and lives. Therefore it is essential to understand the fire performance of light gauge cold-formed steel structures under fire conditions. The buckling behaviour of cold-formed steel compression members under fire conditions is not well investigated yet and hence there is a lack of knowledge on the fire performance of cold-formed steel compression members. Current cold-formed steel design standards do not provide adequate design guidelines for the fire design of cold-formed steel compression members. Therefore a research project based on extensive experimental and numerical studies was undertaken at the Queensland University of Technology to investigate the buckling behaviour of light gauge cold-formed steel compression members under simulated fire conditions. As the first phase of this research, a detailed review was undertaken on the mechanical properties of light gauge cold-formed steels at elevated temperatures and the most reliable predictive models for mechanical properties and stress-strain models based on detailed experimental investigations were identified. Their accuracy was verified experimentally by carrying out a series of tensile coupon tests at ambient and elevated temperatures. As the second phase of this research, local buckling behaviour was investigated based on the experimental and numerical investigations at ambient and elevated temperatures. First a series of 91 local buckling tests was carried out at ambient and elevated temperatures on lipped and unlipped channels made of G250-0.95, G550-0.95, G250-1.95 and G450-1.90 cold-formed steels. Suitable finite element models were then developed to simulate the experimental conditions. These models were converted to ideal finite element models to undertake detailed parametric study. Finally all the ultimate load capacity results for local buckling were compared with the available design methods based on AS/NZS 4600, BS 5950 Part 5, Eurocode 3 Part 1.2 and the direct strength method (DSM), and suitable recommendations were made for the fire design of cold-formed steel compression members subject to local buckling. As the third phase of this research, flexural-torsional buckling behaviour was investigated experimentally and numerically. Two series of 39 flexural-torsional buckling tests were undertaken at ambient and elevated temperatures. The first series consisted 2800 mm long columns of G550-0.95, G250-1.95 and G450-1.90 cold-formed steel lipped channel columns while the second series contained 1800 mm long lipped channel columns of the same steel thickness and strength grades. All the experimental tests were simulated using a suitable finite element model, and the same model was used in a detailed parametric study following validation. Based on the comparison of results from the experimental and parametric studies with the available design methods, suitable design recommendations were made. This thesis presents a detailed description of the experimental and numerical studies undertaken on the mechanical properties and the local and flexural-torsional bucking behaviour of cold-formed steel compression member at ambient and elevated temperatures. It also describes the currently available ambient temperature design methods and their accuracy when used for fire design with appropriately reduced mechanical properties at elevated temperatures. Available fire design methods are also included and their accuracy in predicting the ultimate load capacity at elevated temperatures was investigated. This research has shown that the current ambient temperature design methods are capable of predicting the local and flexural-torsional buckling capacities of cold-formed steel compression members at elevated temperatures with the use of reduced mechanical properties. However, the elevated temperature design method in Eurocode 3 Part 1.2 is overly conservative and hence unsuitable, particularly in the case of flexural-torsional buckling at elevated temperatures.

The importance of fire safety design has been realised due to the ever increasing loss of properties and lives caused by structural failures during fires. In recognition of the importance of fire safety design, extensive research has been undertaken in the field of fire safety of buildings and structures especially over the last couple of decades. In the same period, the development of fire safety engineering principles has brought significant reduction to the cost of fire protection. However the past fire research on steel structures has been limited to heavier, hot-rolled structural steel members and thus the structural behaviour of light gauge cold-formed steel members under fire conditions is not well understood. Since cold-formed steel structures have been commonly used for numerous applications and their use has increased rapidly in the last decade, the fire safety of cold-formed steel structural members has become an important issue. The current design standards for steel structures have simply included a list of reduction factors for the yield strength and elasticity modulus of hot-rolled steels without any detailed design procedures. It is not known whether these reduction factors are applicable to the commonly used thin, high strength steels in Australia. Further, the local buckling effects dominate the structural behaviour of light gauge cold-formed steel members. Therefore an extensive research program was undertaken at the Queensland University of Technology to investigate the local buckling behaviour of light gauge cold-formed steel compression members under simulated fire conditions. The first phase of this research program included 189 tensile coupon tests including three steel grades and six thicknesses to obtain the accurate yield strength and elasticity modulus values at elevated temperatures because the deterioration of the mechanical properties is the major parameter in the structural design under fire conditions. The results obtained from the tensile tests were used to predict the ultimate strength of cold-formed steel members. An appropriate stress-strain model was also developed by considering the inelastic mechanical characteristics. The second phase of this research was based on a series of more than 120 laboratory experiments and corresponding numerical analyses on cold-formed steel compression members to investigate the local bucking behaviour of the unstiffened flange elements, stiffened web elements and stiffened web and flange elements at elevated temperatures up to 800°C. The conventional effective design rules were first simply modified considering the reduced mechanical properties obtained from the tensile coupon tests and their adequacy was studied using the experimental and numerical results. It was found that the simply modified effective width design rules were adequate for low strength steel members and yet was not adequate for high strength cold-formed steel members due to the severe reduction of the ultimate strength in the post buckling strength range and the severe reduction ratio of the elasticity modulus to the yield strength at elevated temperatures. Due to the inadequacy of the current design rules, the theoretical, semi-empirical and empirical effective width design rules were developed to accurately predict the ultimate strength of cold-formed steel compression members subject to local buckling effects at elevated temperatures. The accuracy of these new design methods was verified by comparing their predictions with a variety of experimental and numerical results. This thesis presents the details of extensive experimental and numerical studies undertaken in this research program and the results including comparison with simply modified effective width design rules. It also describes the advanced finite element models of cold-formed steel compression members developed in this research including the appropriate mechanical properties, initial imperfections, residual stresses and other significant factors. Finally, it presents the details of the new design methods proposed for the cold-formed steel compression members subject to local buckling effects at elevated temperatures.

The importance of fire safety design has been realised due to the ever increasing loss of properties and lives caused by structural failures during fires. In recognition of the importance of fire safety design, extensive research has been undertaken in the field of fire safety of buildings and structures especially over the last couple of decades. In the same period, the development of fire safety engineering principles has brought significant reduction to the cost of fire protection. However the past fire research on steel structures has been limited to heavier, hot-rolled structural steel members and thus the structural behaviour of light gauge cold-formed steel members under fire conditions is not well understood. Since cold-formed steel structures have been commonly used for numerous applications and their use has increased rapidly in the last decade, the fire safety of cold-formed steel structural members has become an important issue. The current design standards for steel structures have simply included a list of reduction factors for the yield strength and elasticity modulus of hot-rolled steels without any detailed design procedures. It is not known whether these reduction factors are applicable to the commonly used thin, high strength steels in Australia. Further, the local buckling effects dominate the structural behaviour of light gauge cold-formed steel members. Therefore an extensive research program was undertaken at the Queensland University of Technology to investigate the local buckling behaviour of light gauge cold-formed steel compression members under simulated fire conditions. The first phase of this research program included 189 tensile coupon tests including three steel grades and six thicknesses to obtain the accurate yield strength and elasticity modulus values at elevated temperatures because the deterioration of the mechanical properties is the major parameter in the structural design under fire conditions. The results obtained from the tensile tests were used to predict the ultimate strength of cold-formed steel members. An appropriate stress-strain model was also developed by considering the inelastic mechanical characteristics. The second phase of this research was based on a series of more than 120 laboratory experiments and corresponding numerical analyses on cold-formed steel compression members to investigate the local bucking behaviour of the unstiffened flange elements, stiffened web elements and stiffened web and flange elements at elevated temperatures up to 800°C. The conventional effective design rules were first simply modified considering the reduced mechanical properties obtained from the tensile coupon tests and their adequacy was studied using the experimental and numerical results. It was found that the simply modified effective width design rules were adequate for low strength steel members and yet was not adequate for high strength cold-formed steel members due to the severe reduction of the ultimate strength in the post buckling strength range and the severe reduction ratio of the elasticity modulus to the yield strength at elevated temperatures. Due to the inadequacy of the current design rules, the theoretical, semi-empirical and empirical effective width design rules were developed to accurately predict the ultimate strength of cold-formed steel compression members subject to local buckling effects at elevated temperatures. The accuracy of these new design methods was verified by comparing their predictions with a variety of experimental and numerical results. This thesis presents the details of extensive experimental and numerical studies undertaken in this research program and the results including comparison with simply modified effective width design rules. It also describes the advanced finite element models of cold-formed steel compression members developed in this research including the appropriate mechanical properties, initial imperfections, residual stresses and other significant factors. Finally, it presents the details of the new design methods proposed for the cold-formed steel compression members subject to local buckling effects at elevated temperatures.

Geopolymer has gained its focus recently and are generally believed to have good fire resistance due to their ceramic-like properties. As timber structures are very much popular around the globe and this structure is also very vulnerable to fire so this geopolymer coating can be used to protect the timber from fire to some extent. This research evaluated the effectiveness of fly ash based geopolymer coating to protect the damage of timber against fire.

This research study investigated the fire performance of steel columns strengthened with Carbon Fibre Reinforced Polymers (CFRP). Using thermal and mechanical property tests, full scale fire tests and numerical analyses, it showed that suitable insulation layers can be successfully used to increase their fire resistance to required levels. It then developed new design guidelines to determine the fire resistance of CFRP strengthened and insulated steel columns.

Thin-walled cold-formed steel (CFS) has exhibited inherent structural and architectural advantages over other constructional materials, for example, high strength-to-weight ratio, ease of fabrication, economy in transportation and the flexibility of sectional profiles, which make CFS ideal for modern residential and industrial buildings. They have been increasingly used as purlins as the intermediate members in a roof system, or load-bearing components in low- and mid-rise buildings. However, using CFS members in building structures has been facing challenges due to the lack of knowledge to the fire performance of CFS at elevated temperatures and the lack of fire design guidelines. Among all available design specifications of CFS, EN1993-1-2 is the only one which provided design guidelines for CFS at elevated temperatures, which, however, is based on the same theory and material properties of hot-rolled steel. Since the material properties of CFS are found to be considerably different from those of hot-rolled steel, the applicability of hot-rolled steel design guidelines into CFS needs to be verified. Besides, the effect of non-uniform temperature distribution on the failure of CFS members is not properly addressed in literature and has not been specified in the existing design guidelines. Therefore, a better understanding of fire performance of CFS members is of great significance to further explore the potential application of CFS. Since CFS members are always with thin thickness (normally from 0.9 to 8 mm), open cross-section, and great flexural rigidity about one axis at the expense of low flexural rigidity about a perpendicular axis, the members are usually susceptible to various buckling modes which often govern the ultimate failure of CFS members. When CFS members are exposed to a fire, not only the reduced mechanical properties will influence the buckling capacity of CFS members, but also the thermal strains which can lead additional stresses in loaded members. The buckling behaviour of the member can be analysed based on uniformly reduced material properties when the member is unprotected or uniformly protected surrounded by a fire that the temperature distribution within the member is uniform. However if the temperature distribution in a member is not uniform, which usually happens in walls and/or roof panels when CFS members are protected by plaster boards and exposed to fire on one side, the analysis of the member becomes very complicated since the mechanical properties such as Young’s modulus and yield strength and thermal strains vary within the member. This project has the aim of providing better understanding of the buckling performance of CFS channel members under non-uniform temperatures. The primary objective is to investigate the fire performance of plasterboard protected CFS members exposed to fire on one side, in the aspects of pre-buckling stress distribution, elastic buckling behaviour and nonlinear failure models. Heat transfer analyses of one-side protected CFS members have been conducted firstly to investigate the temperature distributions within the cross-section, which have been applied to the analytical study for the prediction of flexural buckling loads of CFS columns at elevated temperatures. A simplified numerical method based on the second order elastic – plastic analysis has also been proposed for the calculation of the flexural buckling load of CFS columns under non-uniform temperature distributions. The effects of temperature distributions and stress-strain relationships on the flexure buckling of CFS columns are discussed. Afterwards a modified finite strip method combined with the classical Fourier series solutions have been presented to investigate the elastic buckling behaviour of CFS members at elevated temperatures, in which the effects of temperatures on both strain and mechanical properties have been considered. The variations of the elastic buckling loads/moments, buckling modes and slenderness of CFS columns/beams with increasing temperatures have been examined. The finite element method is also used to carry out the failure analysis of one-side protected beams at elevated temperatures. The effects of geometric imperfection, stress-strain relationships and temperature distributions on the ultimate moment capacities of CFS beams under uniform and non-uniform temperature distributions are examined. At the end the direct strength method based design methods have been discussed and corresponding recommendations for the designing of CFS beams at elevated temperatures are presented. This thesis has contributed to improve the knowledge of the buckling and failure behaviour of CFS members at elevated temperatures, and the essential data provided in the numerical studies has laid the foundation for further design-oriented studies.

Cold-formed steel members are extensively used in the building construction industry, especially in residential, commercial and industrial buildings. In recent times, fire safety has become important in structural design due to increased fire damage to properties and loss of lives. However, past research into the fire performance of cold-formed steel members has been limited, and was confined to compression members. Therefore a research project was undertaken to investigate the structural behaviour of compact cold-formed steel lipped channel beams subject to inelastic local buckling and yielding, and lateral-torsional buckling effects under simulated fire conditions and associated section and member moment capacities. In the first phase of this research, an experimental study based on tensile coupon tests was undertaken to obtain the mechanical properties of elastic modulus and yield strength and the stress-strain relationship of cold-formed steels at uniform ambient and elevated temperatures up to 700oC. The mechanical properties deteriorated with increasing temperature and are likely to reduce the strength of cold-formed beams under fire conditions. Predictive equations were developed for yield strength and elastic modulus reduction factors while a modification was proposed for the stressstrain model at elevated temperatures. These results were used in the numerical modelling phases investigating the section and member moment capacities. The second phase of this research involved the development and validation of two finite element models to simulate the behaviour of compact cold-formed steel lipped channel beams subject to local buckling and yielding, and lateral-torsional buckling effects. Both models were first validated for elastic buckling. Lateral-torsional buckling tests of compact lipped channel beams were conducted at ambient temperature in order to validate the finite element model in predicting the non-linear ultimate strength behaviour. The results from this experimental study did not agree well with those from the developed experimental finite element model due to some unavoidable problems with testing. However, it highlighted the importance of magnitude and direction of initial geometric imperfection as well as the failure direction, and thus led to further enhancement of the finite element model. The finite element model for lateral-torsional buckling was then validated using the available experimental and numerical ultimate moment capacity results from past research. The third phase based on the validated finite element models included detailed parametric studies of section and member moment capacities of compact lipped channel beams at ambient temperature, and provided the basis for similar studies at elevated temperatures. The results showed the existence of inelastic reserve capacity for compact cold-formed steel beams at ambient temperature. However, full plastic capacity was not achieved by the mono-symmetric cold-formed steel beams. Suitable recommendations were made in relation to the accuracy and suitability of current design rules for section moment capacity. Comparison of member capacity results from finite element analyses with current design rules showed that they do not give accurate predictions of lateral-torsional buckling capacities at ambient temperature and hence new design rules were developed. The fourth phase of this research investigated the section and member moment capacities of compact lipped channel beams at uniform elevated temperatures based on detailed parametric studies using the validated finite element models. The results showed the existence of inelastic reserve capacity at elevated temperatures. Suitable recommendations were made in relation to the accuracy and suitability of current design rules for section moment capacity in fire design codes, ambient temperature design codes as well as those proposed by other researchers. The results showed that lateral-torsional buckling capacities are dependent on the ratio of yield strength and elasticity modulus reduction factors and the level of non-linearity in the stress-strain curves at elevated temperatures in addition to the temperature. Current design rules do not include the effects of non-linear stress-strain relationship and therefore their predictions were found to be inaccurate. Therefore a new design rule that uses a nonlinearity factor, which is defined as the ratio of the limit of proportionality to the yield stress at a given temperature, was developed for cold-formed steel beams subject to lateral-torsional buckling at elevated temperatures. This thesis presents the details and results of the experimental and numerical studies conducted in this research including a comparison of results with predictions using available design rules. It also presents the recommendations made regarding the accuracy of current design rules as well as the new developed design rules for coldformed steel beams both at ambient and elevated temperatures.

Load bearing Light Gauge Steel Frame (LSF) wall system is a cold-formed steel structure made of cold-formed steel studs and lined on both sides by gypsum plasterboards. In recent times its use and demand in the building industry has significantly increased due to their advantages such as light weight, acoustic performance, aesthetic quality of finished wall, ease of fabrication and rapid constructability. Fire Resistant Rating (FRR) of these walls is given more attention due to the increasing number and severity of fire related accidents in residential buildings that have caused significant loss of lives and properties. LSF walls are commonly made of conventional lipped channel section studs lined with fire resistant gypsum plasterboards on both sides. Recently, greater attention has been given to innovative cold-formed steel sections such as hollow flange sections due to their improved structural efficiency. The reliance on expensive and time consuming full scale fire tests, and the complexity involved in predicting the fire performance of LSF wall studs due to their thin-walled nature and their exposure to non-uniform temperature distributions in fire on one side, have been the main barriers in using different cold-formed steel stud sections in LSF wall systems. This research overcomes this and proposes the new hollow flange section studs as vertical load bearing elements in LSF wall systems based on a thorough investigation into their fire (structural and thermal) performance using full scale fire tests and extensive numerical studies. Test wall frames made of hollow flange section studs were lined with fire resistant gypsum plasterboards on both sides, and were subjected to increasing temperatures as given by the standard fire curve in AS 1530.4 (SA, 2005) on one side. Both uninsulated and cavity insulated walls were tested with varying load ratios from 0.2 to 0.6. LiteSteel Beam (LSB), a welded hollow flange section, which was available in the industry was used to fabricate the test wall panels. Axial deformations and lateral displacements along with the time-temperature profiles of the steel stud and plasterboard surfaces were measured. Five full scale tests were performed, and the test results were compared with those of LSF walls made of lipped channel section studs, which proved the superior fire performance of LSF walls made of hollow flange section studs. The reasons for the superior fire performance are presented in this thesis. The effects of load ratio and plasterboard joint on the fire performance of LSF walls and temperature distribution across the stud cross-sections were identified. Improved plasterboard joints were also proposed. The elevated temperature mechanical properties of cold-formed steels appear to vary significantly as shown by past research. LSBs were manufactured using a combined cold-forming and electric resistance welding process. Elevated temperature mechanical properties of LSB plate elements are unknown. Therefore an experimental study was undertaken to determine the elevated temperature mechanical properties of LSB plate elements. Based on the test results and previous researchers' proposed values, suitable predictive equations were proposed for the elastic modulus and yield strength reduction factors and stress-strain models of LSB web and flange elements. Uninsulated and insulated 2D finite element models of LSF walls were developed in SAFIR using GiD as a pre- and post processor to predict the thermal performance under fire conditions. A new set of apparent thermal conductivity values was proposed for gypsum plasterboards for this purpose. These models were then validated by comparing the time-temperature profiles of stud and plasterboard surfaces with corresponding experimental results. The developed models were then used to conduct an extensive parametric study. Uninsulated and insulated LSF walls with superior fire performances were also proposed. Finite element models of tested walls were also developed and analysed under both transient and steady state conditions to predict the structural performance under fire conditions using ABAQUS. In these analyses, the measured elevated temperature properties of LSB plate elements were used to improve their accuracy. Finite element analysis results were compared with fire test results to validate the developed models. Following this, a detailed finite element analysis based study was conducted to investigate the effects of stud dimensions such as web depths and thicknesses, elevated temperature mechanical properties, types of wall configurations, stud section profiles, plasterboards to stud connections and realistic design fire curves on the fire performance of LSF walls. It was also shown that the commonly used critical temperature method is not appropriate in determining the FRR of LSF walls. Gunalan and Mahendran's (2013) design rules based on AS/NZS 4600 (SA, 2005), and Eurocode 3 Part 1.3 (ECS, 2006) were further improved to predict the structural capacity of hollow flange section studs subjected to non-uniform temperature distributions caused by fire on one side. Two improved methods were proposed and they predicted the FRRs with a reasonable accuracy. Direct Strength Method (DSM) based design rules were then established and they also predicted the FRR of LSF walls made of hollow flange section studs accurately. Finally, spread sheet based design tools were developed based on the proposed design rules. Overall, this research has developed comprehensive fire performance data of LSF walls made of hollow flange section studs, accurate design rules to predict their fire rating and associated design tools. Thus it has enabled the use of innovative hollow flange sections as studs in LSF wall systems. Structural and fire engineers can now use these tools to undertake complex calculations of determining the structural capacities and fire rating of hollow flange section studs subjected to non-uniform temperature distributions, and successfully design them for safe and efficient use in LSF walls of residential and office buildings.

L’impact de l’homme sur l’environnement mondial et sur la diversité et le fonctionnement des écosystèmes terrestres fait l’objet d’une attention croissante. De nombreuses études ont évalué les effets de facteurs du changement global tels sur les processus de cycle de l'azote du sol dans les prairies. Cependant, ces études n'ont pas pris en compte le fait que la modification du régime de précipitations avait également une influence sur le régime de dépôt d'azote. En outre, la réponse du cycle de l'azote dans les sols des prairies à de multiples facteurs du changement global agissant ensemble et parfois en même temps que des perturbations telles que les incendies, doit encore être étudiée. Cela limite fortement notre capacité à comprendre et à prévoir les effets du changement global sur les prairies. Dans ce travail de doctorat, deux expériences ont été menées: (i) une expérience en mésocosme pour évaluer les effets combinés d'une augmentation des dépôts d'azote et de changements dans la quantité et la fréquence des précipitations sur le cycle de l'azote édaphique dans une prairie semi-aride; (ii) une expérience in situ pour évaluer les effets combinés de l'augmentation de la concentration en CO2, du réchauffement, d’une modification des précipitations, du dépôt d'azote et d’un feu sur le cycle de l'azote du sol dans une prairie méditerranéenne. Cela permet d'étudier les effets de la combinaison de plusieurs facteurs de changement global (et d’une perturbation feu) sur l'abondance des communautés microbiennes du cycle de l'azote.Les groupes microbiens étudiés étaient les bactéries et les archées oxydant l'ammoniac (AOB et AOA, respectivement), les réducteurs de nitrite porteuses des gènes nirK ou nirS, et les réducteurs de N2O porteurs des gènes nosZI- et nosZII, plus les bactéries oxydant le nitrite du genre Nitrobacter et Nitrospira pour la prairie méditerranéenne. Les principaux résultats et conclusions sont les suivants: 1) Les réactions des différents groupes de (dé)nitrifiants aux scénarios de changement global différaient fortement quel que soit le type de prairie. Les AOB étaient principalement dépendant de la disponibilité en azote En revanche, dans les deux prairies, les AOA étaient plus sensibles à la dynamique de l'eau du sol que la dynamique de l'azote. L'abondance des Nitrobacter étaient principalement affectée par les facteurs de changement global affectant l'abondance de l'AOB, tandis que l'abondance des Nitrospira était davantage liée aux changements d'abondance des AOA dans la prairie méditerranéenne. 2）Dans la prairie californienne où deux dépôts d'azote élevés avaient lieu chaque année, l'effet de l'azote dominait les effets du changement global. En revanche, dans la prairie chinoise, les dépôts d’azote simulés par des apports chroniques couplés aux événements de précipitation n’augmentaient pas l’abondance des dénitrifiants et ne faisaient que légèrement augmenter les émissions de N2O. 3） Pour les deux prairies, l'interaction entre les facteurs du changement global sur le cycle de l'azote du sol ne pouvait pas être prédite simplement en étudiant les effets d'un ou de deux facteurs. Ces effets interactifs ont pu être expliqués par des effets sur des variables environnementales clés telles que l'humidité du sol, la disponibilité de l'azote minéral, le pH et la croissance des racines. Ces résultats démontrent qu'il est impossible de prédire comment les (dé)nitrifiants et la (dé)nitrification répondent aux scénarios de changement global impliquant de multiples facteurs uniquement à partir de la connaissance d'effets de facteurs étudiés isolément. Cela nécessite donc des études plus approfondies dans le domaine de la biologie des changements globaux. La modélisation et l'évaluation de la généralité de ces effets d'interaction complexes constituent donc une priorité majeure pour les chercheurs qui veulent prédir les réponses du cycle de l'azote dans le sol au changement global et les rétroactions sur le climat
The impact of global environmental changes on the diversity and functioning of terrestrial ecosystems has received increasing attention. Many studies evaluated the effects of single -and less often multiple- global change factors on soil N cycling processes in grasslands. However, these studies have not recognized that altered precipitation regime also has an influence on wet N deposition regime. Further, the response of grassland soil N cycling to co-occurring multiple global change factors and disturbance like fire, and how N cycling response to fire could differ under different global change scenarios, remains unclear. This strongly restricts our ability to understand and predict global change effect on grasslands. In this work, two experiments were conducted: (i) a mesocosm experiment to assess the combined effects of increased N deposition and changes in both the amount and frequency of rainfall on soil N cycling in a semi-arid Monsoon grassland; and (ii) an in situ experiment to assess the combined effects of elevated CO2, warming, increased precipitation, N deposition and fire on soil N cycling in a Mediterranean grassland. This allows studying the -possibly interactive- effects of several global change factors on the abundances of soil N-cycling microbial communities. The microbial groups studied were ammonia oxidizing bacteria and archaea (AOB and AOA, respectively), nirK- and nirS-nitrite reducers, nosZI- and nosZII-N2O reducers, plus Nitrobacter and Nitrospira for the Mediterranean grassland. The main results and conclusions are: 1）The responses of different groups of soil (de)nitrifiers to global change scenarios differed strongly regardless the grassland type. AOB were mostly driven by N. In contrast, AOA were more sensitive to soil water dynamics than N dynamics in both grasslands. Nitrobacter abundance was mostly affected by global change factors through their effects on AOB abundance, whereas Nitrospira abundance was more related to changes of AOA in the Mediterranean grassland. Similarly, nirK- and nirS-harboring nitrite reducers and nosZI-harboring N2O reducers were more sensitive to N deposition than nosZII-harboring N2O reducers, and nirK- and nirS-bacteria positively responded to reduced precipitation. This highlights niche differentiation between them and indicates that the balance between them may be altered in the future; 2）In the Mediterranean grassland, where high N deposition was simulated by two N addition events each year, the N effect dominated global change effects. In contrast, in the Monsson grassland, chronic wet N deposition did not increase denitrifier abundance and only weakly increased soil N2O emissions. This was explained by the efficient capture of added N by the dominant grass species and by the increased plant growth leading to increased transpiration and decreased soil moisture. 3）For both grasslands, the interaction between global change factors on soil N cycling could not be predicted simply by studying the effects of one or two factors. These interactive effects were explained by effects on key environmental variables like soil moisture, mineral N availability, pH and belowground plant growth.These results demonstrates the limitation of predicting how (de)nitrifiers respond to global change scenarios involving multiple factors only from studying single factor effects. Particularly, interactive effects were observed between N deposition, decreased precipitation amount and altered precipitation frequency in the Monsoon grassland; and between fire, N deposition, warming, elevated precipitation and elevated CO2 in the Mediterranean grassland. This calls for more comprehensive studies in the global change biology domain. Modelling and evaluating the generality of these complex interaction effects is thus a high priority for research to predict the responses of soil N cycling processes to global change and feedbacks on climate in the future

This thesis has investigated the material characteristics of the new high-strength steel (HSS) produced by Giflo Steels (F-series steel) using detailed experimental studies involving ambient and elevated temperature mechanical property tests, post-fire mechanical property tests and V-Charpy notch tests for hardness. Its findings have shown that the new F-series steel has an advantage over similar HSS as it has superior post-fire mechanical properties, while retaining also the other mechanical properties within the requirements of relevant design standards.

This study presents the effects of two types of alkali activators (Na and K-based) on the residual mechanical properties of steel fibre reinforced geopolymer concretes (SFRGC) after exposed to various elevated temperatures and compared with those of steel fibre reinforced concrete (SFRC). Results show that the SFRGC containing Na- based activators exhibited much higher residual compressive and indirect tensile strength at all elevated temperatures including at ambient condition than its K-based counterpart and SFRC.

La modélisation numérique des structures bois dans des conditions d’incendie nécessite la connaissance : de la variation des propriétés physiques du bois telles que la conductivité thermique, la chaleur spécifique et la densité en fonction de la température ; de la dégradation thermique du bois au cours des phases de séchage, de pyrolyse et de combustion. En particulier, nous nous sommes intéressés à l’étude du comportement thermomécanique du matériau bois. La loi thermique est décrite par l’équation de la chaleur. Le modèle choisi intègre les trois modes du transfert de chaleur : la conduction, le rayonnement et la convection. La loi mécanique est modélisée dans le cadre de la thermodynamique des processus irréversibles utilisant la notion des variables d’état. Elle tient compte du couplage entre le comportement élastique orthotrope, plastique anisotrope à écrouissage non linéaire isotrope et un endommagement isotrope. L’intégration numérique de la loi mécanique par un schéma implicite itératif combinant la technique du retour radial avec la réduction du nombre des équations est présentée. Le couplage thermomécanique est réalisé, selon l’approche réglementaire de l’Eurocode 5 relatif à la résistance au feu des structures en bois, en appliquant le facteur de réduction Kθ sur la résistance mécanique d’un résineux. Les aspects théoriques et les conditions aux limites associés au modèle thermomécanique sont abordés. L’identification des paramètres du modèle est réalisée sur des données expérimentales obtenues sur des tests réels d’incendie disponibles dans la littérature. À ce titre, plusieurs comparaisons avec différentes applications sont réalisées. Le modèle éléments finis reproduit avec précision la distribution du champ de température dans l’épaisseur des panneaux en bois, la formation du charbon ainsi que l’évolution de la résistance mécanique au cours de l’exposition au feu
Numerical modelling of timber structures in fire conditions requires the knowledge of the variation with temperature of the physical properties of the wood material (the thermal conductivity, the specific heat and the density) in order to take into account the thermal degradation of wood under high temperatures during the drying, pyrolysis and combustion phases, as well as the temperature profiles in the thickness of the surfaces exposed to fire. In particular, this work focusses on the thermomechanical behaviour of timber. The heat transfer analysis is described by the standard equations of heat conduction. It includes the three modes of heat transfer: conduction, radiation and convection. The structural response is modelled within the framework of thermodynamics of irreversible processes using the notion of state variables. It takes into account the coupling between the orthotropic elastic behaviour, the anisotropic plastic behaviour with isotropic nonlinear hardening, and isotropic damage. The numerical integration of the equilibrium equations is carried out with an iterative implicit scheme combining the technique of radial re- turn with the reduction of the number of equations. The thermomechanical coupling is carried out according to the approach recommended by Eurocode 5 for the fire resistance of timber structures by applying the reduction factor Kθ to the strength of a softwood. The theoretical aspects and boundary conditions associated with the thermomechanical model are also discussed. The parameters of the model are identified with experimental data obtained from actual fire tests available in the literature. Several comparative applications are carried out. The finite element model accurately reproduces the distribution of the temperature profile in the thickness of timber planks, the formation of the charred layer, and the evolution of the mechanical resistance during exposure to fire

Concrete is a strong material as to its compressive strength. However, it is a material with a low tensile and shear strength, and brittleness at failure. Concrete has to be reinforced with appropriate materials. Steel fibre is one of the most common materials currently being used to develop reinforced concrete, which may replace partially or completely conventional steel reinforcement. Successful reinforcement of concrete composite is closely related to the bond characteristics between the reinforcing fibre and matrix. The effective utilisation of steel fibre reinforced concrete (SFRC) requires in-depth and detailed understanding of bonding mechanisms governing the tensile behaviour. In response to this demand, this study embraced two main areas: understanding the reinforcing mechanisms of fibres in SFRC and material's post-cracking behaviour. Comprehensive experimental and theoretical programmes have therefore been developed: the experimental work is subdivided into three parts. The first part was to investigate the effect of various physical parameters, such as fibre characteristics (i.e. geometry, inclination angle, embedded length, diameter and tensile strength) and matrix strength which controls the pull-out behaviour of steel fibres. The second part is concerned with the assessment of the bond mechanisms of straight and hooked end fibres after exposure to elevated temperatures and varying matrix strength. The third part is devoted to gain further insight on the bond mechanisms governing the post-cracking behaviour through uniaxial and bending tests. It was found that the varying hook geometry and matrix strength each had a major influence on the pull-out response of hooked end fibres. As the number of the hook's bends increased, the mechanical anchorage provided by fibre resulted in significant improvement of mechanical properties of SFRC. The reduction in bond strength at elevated temperatures is found to be strongly related to the degradation in properties of the constituent materials, i.e. the fibre and concrete. The most effective combination of matrix strength and fibre geometry was found to be as follows: 3DH (single bend) fibre with normal-medium strength matrix, 4DH (double bend) fibre with high strength matrix and 5DH (triple bend) fibre with ultra-high performance matrix. Two analytical models to predict the pull-out behaviour of hooked end fibres were developed. Both models were able to predict the pull-out response of SFRC made from a variety of fibre and matrix characteristics at ambient temperature. This work has established a comprehensive database to illustrate the bonding mechanisms of SFRC and anchorage strengthening of various hooked end fibres, and this should contribute towards an increasing interest and growing number of structural applications of SFRC in construction.

The range and use of the tenor voice in classical music has long been established since the late 19th century. It is widely accepted among pedagogues that the range is C3-C5 (with obvious exceptions depending on the fach). However, with the advent and development of the American Musical as a genre since the early 20th century, the ‘tenor’ has taken on an entirely new direction and range altogether. Several well-known sources have stated that the ‘Broadway tenor’ has a range of A2-A4. This is (as it widely accepted in the classical profession) the range of a baritone. The catalyst of these changes include vaudeville, composers, social trends, and probably most important, the invention and proliferation of the microphone. This study will analyze a cross section of repertoire in order to demonstrate this downward shift of vocal range, and demonstrate some of the main reasons why this shift occurred.

L’obiettivo principale dell’elaborato è stato quello di analizzare la diagnosi del catalizzatore e delle sonde lambda durante i cicli di guida previsti dalle normative NEDC e WLTP. la diagnosi costituisce un’azione intrusiva durante la quale il catalizzatore non lavora in maniera ottimale. Il fulcro dello studio verte, sul riconoscimento dei parametri critici che non permettono la corretta riuscita della diagnosi, e come essa impatta sulle emissioni inquinanti, in particolare HC, CO e NOx. È stato implementato e validato un modello simulink utile per effettuare delle analisi. Da tali analisi si è evinto che i parametri critici da cui dipende il fallimento della diagnosi sono il rendimento volumetrico e la portata dei gas di scarico in ingresso al catalizzatore, poiché sono impostate delle soglie di calibrazione per le quali, qualora queste due variabili vadano sottosoglia la diagnosi viene abortita. La conclusione dello studio ha portato al risultato per il quale è possibile utilizzare come principale parametro la portata dei gas di scarico al posto del rendimento volumetrico. Difatti, eliminando la dipendenza dal rendimento volumetrico, non si è più legati al regime del motore e non vi è differenza se l’utilizzo della vettura viene fatto in modalità normale o in modalità SPORT (cambia lo shift pattern del cambio). Inoltre, si può evitare l’attivazione della diagnosi per tempi brevi, che non consentirebbero la buona riuscita, lavorando sulla soglia inerente alla massa di gas accumulata nel catalizzatore. Nella fattispecie, a valle di un’analisi statistica effettuata su più misure, nelle quali viene calcolata la massa immagazzinata durante le diagnosi fallite, si può impostare un valore di soglia minimo di massa. Tale valore minimo può essere scelto in modo tale che vada ad escludere i tentativi in cui il valore della portata dei gas di scarico si trova sopra la soglia della portata ma per un tempo breve che non consentirebbe la buona riuscita della diagnosi.

La stabilità degli argini fluviali è un tema che assume oggi maggiore rilievo per effetto degli eventi estremi di piena indotti dai cambiamenti climatici. I conseguenti gradienti idraulici che si determinano innescano fenomeni tra i quali quello più dannoso è il Backward Erosion Piping. Questo consiste nello sviluppo di un tubo di erosione che corre al di sotto della struttura arginale collegando il punto di uscita a valle con il corpo idrico a monte. L’effetto è un’accelerazione del fenomeno di erosione che può portare in breve tempo a cedimenti arginali. Le tecniche di prevenzione attuali spesso riescono solamente a ritardare il crollo, oltre ad essere di grande impatto per l’ambiente circostante. Sono quindi allo studio tecnologie alternative ecosostenibili ed in questo contesto si inserisce la tecnologia Coarse Sand Barrier al centro delle attività sperimentali previste dal progetto LIFE Sand Boil coordinato dall’Università di Bologna. Esso si pone l’obiettivo di indagare questa tecnologia attraverso prove sperimentali in laboratorio ed in campo, in modo da valutarne la replicabilità. A causa delle potenziali criticità legate all'implementazione diretta della soluzione ingegneristica proposta nei tratti fluviali interessati, verrà dapprima realizzato un prototipo da laboratorio. L’obiettivo di questa tesi è la progettazione e la verifica sperimentale del circuito idraulico a supporto della sperimentazione geotecnica prevista in laboratorio dal progetto LIFE Sand Boil. Partendo dai parametri geotecnici di riferimento per l’esecuzione dei test, l’attenzione è stata rivolta particolarmente al sistema idraulico e alle tecniche di monitoraggio delle grandezze in gioco. A tal proposito è stato realizzato un prototipo in scala minore così da testare la funzionalità delle scelte progettuali effettuate. Una volta verificato che il tutto funzionasse, si è passati al dimensionamento del circuito idraulico del prototipo vero e proprio previsto dal progetto LIFE San Boil.

This thesis describes the design and processing of project documentation multifunctional house. The multifunctional building is located in the central part of the city of Brno, in the district of Štýřice. This is a five-storey, basementless building with a flat roof on two levels. The building is based on foundations made of plain concrete. Supporting, peripheral and partition walls are designed from ceramic blocks POROTHERM. Ceiling construction is designed to be assembled of ceramic ceiling fittings MIAKO stored on POT beams. External walls of all floors are insulated using an external ETICS with thermal insulation made of mineral wool, which is replaced by XPS polystyrene used for plinth. Part of the facade is designed as ventilated, consisting of trusses of wood and sheathed by cladding panels CEMBRIT METRO. This architecturally divide the building into separate units. The building includes parts of the administrative, residential parts and parts for business purposes. On the first floor there are areas of common storage area of the apartment house, the main utility room, utility room. Furthermore, there is an administrative part, where are the reception facilities for reception, sanitary facilities for employees and office work. Part of the first floor is also a small shop with warehouse and facilities for employees. The second floor is a residential unit and the second part of the administrative unit. Third to the fifth floor is only residential and there are 6 residential units. All floors are connected by staircase and a wheelchair lift. In front of the building is designed parking lot for 20 cars. One of the parking space is wheelchair accessible.

This diploma thesis presents available FRP software for calculating load bearing capacity of the structures reinforced with FRP and compares them between each other. Furthermore theory and algorithm of my own software is presented here. Load bearing capacity of structures which are reinforced with non-metallic reinforcement and loaded by combination of normal force and bending moment can be solved by my programme. Effects of high temperatures on the concrete structures can be included in the calculation. In the second part of the thesis is calculated load-bearing capacity and deflection of the real beam reinforced with FRP reinforcement and load-bearing capacity of member with FRP reinforcement with effect of elevated temperature. This has been done using my software. Comparison of results from hand calculation and laboratory load-bearing testing is done at the end. This laboratory testing was accomplished by Institute of Concrete and Mansory Structures at our faculty.

Diploma thesis "Reconstruction of Restaurant with Housing Facilities Extension" is processed in the form of project documentation for building construction according to the applicable regulations (Act No. 183/2006 Coll., On Zoning and Building Regulations, including subsequent amendments). The project deals with the reconstruction of the existing restaurant building in the village Lísek, No. 89. The building is located on plot No. 49 in the cadastral Lhota u Lisku. Floor plan of the existing building is in rectangular shape with almost the unused basement and a deck above. The 1st underground floor is currently used only technical room and garage. In the 1st floor there is the sales area of restaurant, large kitchen and rooms for staff. Existing structures do not show signs of major damage. Reconstruction is not due to the technical condition of the building, but due to operationally unsatisfactory disposition and investor requiring to create an accommodation capacity. The requirement was to build new rooms to accommodate 24 persons. The supporting structural system of the 2nd floor is designed of ceramic bricks and 3rd floor due to the resistance of existing constructions is newly designed as wooden sandwich. The window openings are fitted with a six-chamber windows with triple insulation. Horizontally extension of the existing building corresponds to the current object. The roof of the building is gabled with dormers lighting the rooms in the 3rd floor. The building is designed so that even after the reconstruction match an existing installation. Part of building construction works is also landscaping. Due to the partial change in purpose of the building was necessary to design a suitable parking space with adequate capacity.

Despite significant efforts have been directed toward reducing waste generation and encouraging alternative waste management strategies, landfills still remain the main option for Municipal Solid Waste (MSW) disposal in many countries. Hence, landfills and related impacts on the surroundings are still current issues throughout the world. Actually, the major concerns are related to the potential emissions of leachate and landfill gas into the environment, that pose a threat to public health, surface and groundwater pollution, soil contamination and global warming effects. To ensure environmental protection and enhance landfill sustainability, modern sanitary landfills are equipped with several engineered systems with different functions. For instance, the installation of containment systems, such as bottom liner and multi-layers capping systems, is aimed at reducing leachate seepage and water infiltration into the landfill body as well as gas migration, while eventually mitigating methane emissions through the placement of active oxidation layers (biocovers). Leachate collection and removal systems are designed to minimize water head forming on the bottom section of the landfill and consequent seepages through the liner system. Finally, gas extraction and utilization systems, allow to recover energy from landfill gas while reducing explosion and fire risks associated with methane accumulation, even though much depends on gas collection efficiency achieved in the field (range: 60-90% Spokas et al., 2006; Huitric and Kong, 2006). Hence, impacts on the surrounding environment caused by the polluting substances released from the deposited waste through liquid and gas emissions can be potentially mitigated by a proper design of technical barriers and collection/extraction systems at the landfill site. Nevertheless, the long-term performance of containment systems to limit the landfill emissions is highly uncertain and is strongly dependent on site-specific conditions such as climate, vegetative covers, containment systems, leachate quality and applied stress. Furthermore, the design and operation of leachate collection and treatment systems, of landfill gas extraction and utilization projects, as well as the assessment of appropriate methane reduction strategies (biocovers), require reliable emission forecasts for the assessment of system feasibility and to ensure environmental compliance. To this end, landfill simulation models can represent an useful supporting tool for a better design of leachate/gas collection and treatment systems and can provide valuable information for the evaluation of best options for containment systems depending on their performances under the site-specific conditions. The capability in predicting future emissions levels at a landfill site can also be improved by combining simulation models with field observations at full-scale landfills and/or with experimental studies resembling landfill conditions. Indeed, this kind of data may allow to identify the main parameters and processes governing leachate and gas generation and can provide useful information for model refinement. In view of such need, the present research study was initially addressed to develop a new landfill screening model that, based on simplified mathematical and empirical equations, provides quantitative estimation of leachate and gas production over time, taking into account for site-specific conditions, waste properties and main landfill characteristics and processes. In order to evaluate the applicability of the developed model and the accuracy of emissions forecast, several simulations on four full-scale landfills, currently in operative management stage, were carried out. The results of these case studies showed a good correspondence of leachate estimations with monthly trend observed in the field and revealed that the reliability of model predictions is strongly influenced by the quality of input data. In particular, the initial waste moisture content and the waste compression index, which are usually data not available from a standard characterisation, were identified as the key unknown parameters affecting leachate production. Furthermore, the applicability of the model to closed landfills was evaluated by simulating different alternative capping systems and by comparing the results with those returned by the Hydrological Evaluation of Landfill Performance (HELP), which is the most worldwide used model for comparative analysis of composite liner systems. Despite the simplified approach of the developed model, simulated values of infiltration and leakage rates through the analysed cover systems were in line with those of HELP. However, it should be highlighted that the developed model provides an assessment of leachate and biogas production only from a quantitative point of view. The leachate and biogas composition was indeed not included in the forecast model, as strongly linked to the type of waste that makes the prediction in a screening phase poorly representative of what could be expected in the field. Hence, for a qualitative analysis of leachate and gas emissions over time, a laboratory methodology including different type of lab-scale tests was applied to a particular waste material. Specifically, the research was focused on mechanically biologically treated (MBT) wastes which, after the introduction of the European Landfill Directive 1999/31/EC (European Commission, 1999) that imposes member states to dispose of in landfills only wastes that have been preliminary subjected to treatment, are becoming the main flow waste landfilled in new Italian facilities. However, due to the relatively recent introduction of the MBT plants within the waste management system, very few data on leachate and gas emissions from MBT waste in landfills are available and, hence, the current knowledge mainly results from laboratory studies. Nevertheless, the assessment of the leaching characteristics of MBT materials and the evaluation of how the environmental conditions may affect the heavy metals mobility are still poorly investigated in literature. To gain deeper insight on the fundamental mechanisms governing the constituents release from MBT wastes, several leaching experiments were performed on MBT samples collected from an Italian MBT plant and the experimental results were modelled to obtain information on the long-term leachate emissions. Namely, a combination of experimental leaching tests were performed on fully-characterized MBT waste samples and the effect of different parameters, mainly pH and liquid to solid ratio (L/S,) on the compounds release was investigated by combining pH static-batch test, pH dependent tests and dynamic up-flow column percolation experiments. The obtained results showed that, even though MBT wastes were characterized by relatively high heavy metals content, only a limited amount was actually soluble and thus bioavailable. Furthermore, the information provided by the different tests highlighted the existence of a strong linear correlation between the release pattern of dissolved organic carbon (DOC) and several metals (Co, Cr, Cu, Ni, V, Zn), suggesting that complexation to DOC is the leaching controlling mechanism of these elements. Thus, combining the results of batch and up-flow column percolation tests, partition coefficients between DOC and metals concentration were derived. These data, coupled with a simplified screening model for DOC release, allowed to get a very good prediction of metal release during the experiments and may provide useful indications for the evaluation of long-term emissions from this type of waste in a landfill disposal scenario. In order to complete the study on the MBT waste environmental behaviour, gas emissions from MBT waste were examined by performing different anaerobic tests. The main purpose of this study was to evaluate the potential gas generation capacity of wastes and to assess possible implications on gas generation resulting from the different environmental conditions expected in the field. To this end, anaerobic batch tests were performed at a wide range of water contents (26-43 %w/w up to 75 %w/w on wet weight) and temperatures (from 20-25 °C up to 55 °C) in order to simulate different landfill management options (dry tomb or bioreactor landfills). In nearly all test conditions, a quite long lag-phase was observed (several months) due to the inhibition effects resulting from high concentrations of volatile fatty acids (VFAs) and ammonia that highlighted a poor stability degree of the analysed material. Furthermore, experimental results showed that the initial waste water content is the key factor limiting the anaerobic biological process. Indeed, when the waste moisture was lower than 32 %w/w the methanogenic microbial activity was completely inhibited. Overall, the obtained results indicated that the operative conditions drastically affect the gas generation from MBT waste, in terms of both gas yield and generation rate. This suggests that particular caution should be paid when using the results of lab-scale tests for the evaluation of long-term behaviour expected in the field, where the boundary conditions change continuously and vary significantly depending on the climate, the landfill operative management strategies in place (e.g. leachate recirculation, waste disposal methods), the hydraulic characteristics of buried waste, the presence and type of temporary and final cover systems.

Fibre reinforced polymer (FRP) materials have been a material of interest in the field of structural engineering due to their superior mechanical properties such as high strength to weight ratios and resistance to environmental degradation and corrosion. Even though research has established the material to be a viable option for construction they are highly susceptible to elevated temperatures. There are several systems available on the market and a great deal of research needs to be conducted to investigate the change in properties and different behaviour at elevated temperature to serve as a better basis for design. The main objective of this project and the experimental program presented in this thesis is to study the thermo mechanical properties of the available systems on the market. A summary of the previous research done in the area covering other materials is presented providing an introduction to the behaviour of different systems under elevated temperature. Then, two different experimental programs are presented. The first considers the glass transition temperature and thermal decomposition of the different systems and the second examines the tensile strength of the different systems under different temperature regimes. The results of both experimental programs are presented and then a connection between the thermo mechanical properties of the resins and the overall strength of the system is established. The research demonstrates that the glass transition temperature of the resin used for an FRP strengthening system is the main determinant of the performance at high temperatures.
Thesis (Master, Civil Engineering) -- Queen's University, 2011-06-16 09:21:32.228

This dissertation presents the results of experimental and computational investigations on the behavior of steel simple beam end framing connections subjected to fire. While significant progress has been made in understanding the overall structural response of steel buildings subject to fire, the behavior of connections under fire conditions is not well understood. Connections are critical elements for maintaining the integrity of a structure during a fire. Fire can cause large force and deformation demands on connections during both the heating and cooling stages, while reducing connection strength and stiffness. Of particular importance are simple beam end framing connections. These are the most common type of connection found in steel buildings and are used at beam-to-girder and girder-to-column connections in the gravity load resisting system of a building. This dissertation focuses on one particular type of beam end connection: the single plate connection, also known as a shear tab vii connection. This connection is very commonly used in U.S. building construction practice. In this study, material properties of ASTM A992 structural steel at elevated temperatures up to 900°C were investigated by steady state tension coupon tests. Experimental studies on the connection subassemblies at elevated temperatures were conducted to understand and characterize the connection strength and deformation capacities, and to validate predictions of connection capacity developed by computational and design models. In the computational studies, a three-dimensional finite element connection model was developed incorporating contact, geometric and material nonlinearity temperature dependent material properties. The accuracy and limitations of this model were evaluated by comparison with experimental data developed in this research as well as data available in the literature. The computational studies investigated the typical behavior of the connection during heating and cooling phases of fires as well as the connection force and deformation demands. The finite element model was further used to study and understand the effects of several key building design parameters and connection details. Based on the test and analysis results, some important finding and conclusions are drawn, and future work for simple shear connection performance in fire are discussed.
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Recently in the United States, there has been increasing interest in developing engineered approaches to structural fire safety of buildings as an alternative to conventional code-based prescriptive approaches. With an engineered approach, the response of a structure to fire is computed and appropriate design measures are taken to assure acceptable response. In the case of steel buildings, one of the key elements of this engineered approach is the ability to predict the elevated-temperature properties of structural steel. Although several past research studies have examined elevated-temperature properties of structural steel, there are still major gaps in the experimental database and in the available constitutive models, particularly for ASTM A992 structural steel, a commonly used grade. Accordingly, the overall objective of this dissertation is to significantly enlarge the experimental database of the elevated-temperature properties for ASTM A992 structural steel and developing improved constitutive models for application in structural-fire engineering analysis. Specific issues examined in this dissertation include the following: tensile properties at elevated temperatures; room-temperature mechanical properties after heating and cooling; and creep and relaxation properties at elevated temperatures. For the elevated-temperature studies of tension, creep and relaxation, constitutive models were developed to describe the measured experimental data. These models were compared to existing theoretical and empirical models from the literature.
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The use of fibre reinforced polymer (FRP) composites for strengthening reinforced concrete structures has become increasingly popular in recent years. However, before FRPs can be implemented in interior building applications their performance during fire must be assessed and understood. There currently remains a paucity of information in this area for most currently available FRP strengthening systems. This thesis presents a study of the mechanical and bond properties of selected currently available FRP strengthening systems for concrete structures at elevated temperatures such as might be experienced during a fire. Testing has been performed and is reported to study the continuous unidirectional coupon tensile strength, lap-splice FRP-to- FRP shear bond strength and tensile elastic modulus at elevated temperatures. Results of thermal characterization tests are also completed in an attempt to relate properties of the polymer matrix, such as the glass transition temperature, and thermal decomposition temperature to the losses of strength and stiffness observed for FRP coupons during steady-state and transient exposure to elevated temperatures up to 200oC. A simple analytical model is presented, for which the input parameters can be determined using dynamic mechanical thermal analysis and thermogravimetric analysis, to describe the reduction in mechanical and bond properties of the FRP systems at elevated temperatures. Based on this testing and subsequent analysis it is recommended that a conservative limit on the allowable temperature exposure for FRP systems during fire be set as the glass transition temperature measured using dynamic mechanical thermal analysis. Furthermore it is suggested that differential scanning calorimetry may not be an appropriate method of determining the glass transition temperature for available FRP systems used in concrete strengthening applications.
Thesis (Master, Civil Engineering) -- Queen's University, 2013-04-30 19:06:24.31

Unbonded post-tensioned concrete slabs have been widely used in Canada and the United States since the 1960s, as they allow increased span-to-depth ratios and excellent control of deflections compared to non-prestressed reinforced concrete flexural members. The satisfactory fire performance of unbonded post-tensioned concrete slabs in North America was established by a series of standard fire tests performed in the United States during the 1960s. However, there is a paucity of data on the effect of elevated temperatures on cold-drawn prestressing steel, both in terms of post-fire residual mechanical properties and high-temperature stress relaxation, which can lead to significant prestress loss both during and after a fire. A detailed and comprehensive literature review is presented that provides background on the residual mechanical properties of prestressing steel, as well as on the creep-relaxation behaviour experienced at elevated temperatures under stress. The results of two test series are discussed; the first examining the effects of elevated temperatures on the residual mechanical properties of prestressing steel exposed to elevated temperatures. The second test series examines the irrecoverable and significant loss of prestress force that results from steel relaxation and other thermal effects experienced during heating. A preliminary analytical model is presented, capable of predicting the change in prestress force experienced by a stressed strand under transient heating. The model is then compared with experimental elevated temperature relaxation data. Finally, the analytical model developed and residual mechanical properties obtained through experimentation are used along with a pre-existing finite difference heat transfer model (developed for concrete slabs) to examine the effect of elevated temperature exposure on the residual flexural capacity of a typical unbonded post-tensioned example slab. Several parameters, such as heated length and concrete cover, are examined using the example structure. From this it was observed that, after one hour of exposure to a standard fire (ASTM E119), significant losses in effective prestress and moment capacity occurred even with the appropriate amount of concrete cover. This is a finding which is of the utmost practical importance to engineers engaged in the evaluation of fire damaged unbonded post-tensioned structures.
Thesis (Master, Civil Engineering) -- Queen's University, 2007-12-18 17:15:17.521
Natural Sciences and Engineering Research Council of Canada, and the Department of Civil Engineering at Queen’s University

碩士
國立成功大學
土木工程學系碩博士班
96
This study performed the three-dimensional nonlinear finite element (FE) analyses using a general purpose finite element program ABAQUS to simulate the structural behaviors of two full-scale H-beam to box-column subassemblage specimens in fire test. In the experimental program of this study, the two specimens were tested at elevated temperatures in the furnace and under the specified constant loadings, and the moment connections of the two specimens were made of fire-resistant steel and normal steel respectively for comparison. The numerical results from ABAQUS were compared with the test results from the experimental program for validation. The three-dimensional solid elements were used in the FE modeling for the two specimens, and both material and geometric nonlinearities were considered in the FE analyses. In order to simulate the realistic behavior of the splice connections in the specimens, the detailed contact modeling was built at the contact surfaces of beam webs, splice plates and bolts. The “sequentially coupled thermal-stress analysis” was employed in this study to conduct the coupled heat transfer and structural analyses for the two specimens at elevated temperatures. After the detailed comparison, the numerical results were in good agreement with the fire test results in specimen deformations, local buckling positions and specimen failure temperatures. In addition, the test and numerical results show that the moment connection made of fire-resistant steel has much better fire-resistant performance than the normal steel moment connection.

The essence of performance-based structural fire safety design of steel building structures is the ability to predict thermal and structural response to fire. An important aspect of such predictions is the ability to evaluate strength of columns at elevated temperatures. Columns are critical structural elements, and failure of columns can lead to collapse of a structure. The ability of steel columns to carry their design loads is greatly affected by timeand temperature-dependent mechanical properties of steel at high temperatures due to fire. It is well known that structural steel loses strength and stiffness with temperature, especially at temperatures above 400 °C. Further, the reductions in strength and stiffness of steel are also dependent on the duration of exposure to elevated temperatures. The time-dependent response or creep of steel plays a particularly important role in predicting the collapse load of steel columns subjected to fire temperatures. Specifically, creep of steel leads to the creep buckling phenomenon, where the critical buckling load for a steel column depends not only on slenderness and temperature, but also on duration of exposure to fire temperatures. The main focus of the research summarized in this dissertation is on a testing program to investigate the effects of time-dependent material behavior or creep on buckling of steel columns subjected to fire. Material characterization tests were conducted at temperatures up to 1000 °C to evaluate tensile and creep properties of ASTM A992 steel at elevated temperatures. In addition, buckling tests on W4×13 wide flange columns under pin-end conditions were conducted to characterize short-time and vii creep buckling phenomena at elevated temperatures. The column test results are further used to verify analytical and computational tools developed to model the time-dependent buckling of steel columns at elevated temperatures. Test results are also compared against code-based predictions such as those from Eurocode 3 and the AISC Specification. Results of the research study presented in this dissertation clearly indicate that thermal creep of steel has a very large effect on strength of steel columns at high temperatures due to fire. The effect of creep on column capacity at high temperatures can be predicted using analytical and computational approaches presented in this dissertation.
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Fibre reinforced polymers (FRPs) have gained considerable popularity as a building and repair material. In particular, FRPs have been an economical means of extending the life of structures. As time passes, an increased number and variety of new and old structures are incorporating FRPs as reinforcement and for rehabilitation. Perhaps most common are their applications for bridge structures. Much of the reluctance towards the inclusion of FRP as primary reinforcement or as a rehabilitation measure in building structures is due to its poor performance in fires. In order to move forward with an understanding of how FRP may overcome its temperature-related short comings, it is important to explore the behaviour of FRP, and structures which utilize FRP for reinforcement, at elevated temperatures. The results of a testing program including eleven high temperature, two room temperature intermediate-scale, FRP-strengthened, and one unstrengthened reinforced concrete beam tests are presented. The elevated temperature tests were conducted on both un-post-cured and post-cured FRP strengthening at temperatures up to 211°C. The tests also utilized a novel method for heating and post-curing FRP-strengthening in place. The strengthened beams exhibited strength gains above the unstrengthened reference beam, and it has been demonstrated that post-curing of an FRP system can be effective at increasing an FRP’s performance at elevated temperatures. Exposed to constant temperatures, un-post-cured specimens still exhibited substantial FRP strength at exposure temperatures up to Tg+79°C. Post-cured specimens exhibited similar performance at temperatures of Tg+43°C. The transient temperature tests resulted in ii beam failure at an average temperature of 186°C and 210°C for un-post-cured and post-cured FRP strengthening respectively at a constant applied load level 93% of that of the room temperature strengthened control beam. The results of this testing program demonstrate that FRP strengthening can remain effective when exposed to temperatures well above the measured value of Tg.
Thesis (Master, Civil Engineering) -- Queen's University, 2013-02-28 15:14:31.336

碩士
國立成功大學
土木工程學系
102
The Numerical Simulations for the Fire-Resistance Enhancement Strategies of Concrete-Filled Steel Box Columns at Elevated Temperatures Author: Kao-Chu Chien Advisor: Professor Hsin-Yang Chung Department of Civil Engineering National Cheng Kung University SUMMARY This thesis utilized the numerical models developed by a three-dimensional nonlinear finite-element program to simulate the structural behaviors of concrete-filled box columns (CFBCs) with the constant axial compressive load at elevated temperatures. The numerical models employed the sequentially coupled thermal-stress analysis to conduct heat transfer and structural analyses for the CFBCs with the constant axial compression and elevated by the ISO-834 time-temperature curve. First, this thesis conducted parameter analyses for column length, load ratio, concrete strength and column plate thickness of CFBCs to investigate the failure temperatures and the failure modes of CFBCs, and to understand the influences of the four parameters on the high temperature structural behaviors of the CFBCs. In addition, this thesis also performed numerical simulations, analyses and comparisons for five kinds of fire-resistant enhancement strategies (including the normal steel column-plate stiffener strengthening method, the fire-resistant steel column-plate stiffener strengthening method, the interior cross-shaped normal steel stiffener strengthening method, the interior cross-shaped fire-resistant steel stiffener strengthening method and the fire-resistant steel column plate strengthening method) to find the best strategy of improving failure temperature and the most economical strategy of improving fire resistance. The numerical simulation results showed that the interior cross-shaped fire-resistant steel stiffener strengthening method demonstrated the best failure temperature improvement strategy, which could improve failure temperature by 21.3%. The interior cross-shaped normal steel stiffener strengthening method was the most economical strategy of improving fire resistance. Key words：Concrete-Filled Steel Box Column, Fire, Nonlinear Finite-Element Method, Failure Temperatures, Enhancement Strategies. INTRODUCTION The tall building designs in Taiwan frequently adopt steel structures. One benefit is to decrease the self weight of building by reducing column size. The other benefit is to increase the bay length (i.e. beam length) and the usable floor area. Considering the seismic effects, structural designs in Taiwan for beam-to-column connections especially pay more attention on the ductility and toughness. The design concept of “Strong Column and Weak Beam” are always adopted in building design. As a result, steel column constructions in Taiwan usually utilize the design of concrete-filled box column (CFBC). The CFBCs are different from the steel reinforced concrete columns in which steel is covered by concrete against fire. The CFBCs are frequently utilized in the columns of the lower floors because they bear the heavy weights of the upper floors. In CFBCs, the steel box bears more load than the infilled concrete. In fire, the stiffness and strength of steel decrease when the fire temperature increases. This jeopardizes the structural safety of steel buildings. How to increase the fire-resistance of the CFBCs is very important. Our group have successfully simulated the three-dimensional nonlinear finite-element steel H-shaped frame model at elevated temperatures with a finite-element program and have successfully strengthened a three-dimensional nonlinear finite-element steel H-shaped frame model at elevated temperatures using fire-resistance steel. I will continue our research group’s works to develop the CFBC numerical models using the three-dimensional nonlinear finite-element program to investigate the structural behaviors of the CFBCs with the constant axial compressive load at elevated temperatures and to find the best strategy of improving failure temperature and the most economical strategy of improving fire resistance from the five kinds of fire-resistant enhancement strategies, including the normal steel column-plate stiffener strengthening method, the fire-resistant steel column-plate stiffener strengthening method, the interior cross-shaped normal steel stiffener strengthening method, the interior cross-shaped fire-resistant steel stiffener strengthening method and the fire-resistant steel column plate strengthening method. MATERIALS AND METHODS Research methods were mainly divided into three parts. The first part was that three-dimensional nonlinear finite-element CFBCs numerical models were developed and were verified by the experiment to confirm each step of the model establishments correct. The second part was employed the sequential heat transfer and stress analysis to simulate the surface of CFBCs numerical models heated by ISO-834 time-temperature curve in constant load. Parameter analyses were divided into column length, load ratio, concrete strength and column plate thickness of CFBCs to investigate the numerical results and to realize the effects of the CFBCs by each parameter model at elevated temperature. The third part was employed the sequential heat transfer and stress analysis to simulate the surface of CFBCs numerical strengthening models heated by ISO-834 time-temperature curve in constant load. Enhancement strategies were divided into the steel column-plate stiffener strengthening method, the interior cross-shaped steel stiffener strengthening method, the fire-resistant steel column plate strengthening method and etc. to research for the best economical strategy of improving fire resistance. RESULTS AND DISCUSSION The results of column length parameter analyses in the same load ratio were showed that failure temperature of the long length column was higher than failure temperature of the short length column. The normal compression strength of the long column is lower than the normal compression strength of the short column at room temperature, so the long column bears the lower compression than the short column in the same load ratio. The normal compression strength decreased in high temperatures, so the failure temperature of the long column bearing the lower compression was higher than the failure temperature of the short column bearing the higher compression as Figure 5-87. The results of column length parameter analyses in the same load (13970 kN) were showed that failure temperature of the long length column was lower than failure temperature of the short length column. The normal compression strength decreased in high temperatures, so the failure temperature of the short column was higher than the failure temperature of the long column as Figure 5-88. The results of load ratio parameter analyses were showed that failure temperature of the high ratio column was lower than failure temperature of the low ratio column in the same section size as Figure 5-89. According to my research, it was illustrated that the failure temperature was decreased in 60˚C per increasing load ratio by every 10%. The results of concrete strength parameter analyses in the same load ratio were showed that failure temperature of the high strength concrete column was higher than failure temperature of the low strength concrete column in the same size section as Figure 5-90. Concrete temperature was low at elevated temperature due to the poor concrete conductivity, so concrete could bear the part axial force. The failure temperature of CFBCs was improved by increasing the concrete compression strength. The results of column plate thickness of CFBCs parameter analyses in the same load ratio were showed that failure temperature of the thin plate column was higher than failure temperature of the thick plate column. The normal compression strength of the thick plate column is higher than the normal compression strength of the thin plate column at room temperature, so the thick plate column bears the higher compression than the thin plate column in the same load ratio. The failure temperature of the thick plate column bearing the higher compression was lower than the failure temperature of the thin plate column bearing the lower compression but the 25 mm plate thickness had the local maximum failure temperature and the failure temperature was increased in plate thickness 22 mm to 25 mm as Figure 5-69. The results of column plate thickness of CFBCs parameter analyses in the same load (13970 kN) were showed that failure temperature of the thick plate column was higher than failure temperature of the thin plate column. The normal compression strength of the thick plate column is higher than the normal compression strength of the thin plate column at room temperature. The normal compression strength was decreased in high temperatures, so the failure temperature of the thick plate column was higher than the failure temperature of the thin plate column in the constant load as Figure 5-91. The results of the CFBCs strengthening models were showed that the fire-resistance steel was better the normal steel to improve failure temperature of the CFBCs as the interior cross-shaped fire-resistant steel stiffener strengthening method (20mm×120mm) which could improve failure temperature by 21.3%. The interior cross-shaped steel stiffener strengthening method was better than steel column-plate stiffener strengthening method to improve failure temperature due to the interior cross-shaped steel stiffener strengthening method covering by concrete against fire to keep the stiffness and strength. CONCLUSION The results of the concrete-filled steel box column exposed to standard fire were showed as follows： (1) The failure temperature of the long length column was higher than failure temperature of the short length column in the same load ratio. (2) The failure temperature of the long length column was lower than failure temperature of the short length column in the constant load. (3) The failure temperature of the high ratio column was lower than failure temperature of the low ratio column in the same size section. (4) The failure temperature of the high strength concrete column was higher than failure temperature of the low strength concrete column in the same size section. (5) The failure temperature of the thick plate column was higher than failure temperature of the thin plate column in the constant load. (6) The interior cross-shaped fire-resistant steel stiffener strengthening method (20mm×120mm) improved failure temperatures by 21.3%. (7) The interior cross-shaped normal steel stiffener strengthening method was the most economical strategy of improving fire resistance.

Rectangular thin-walled concrete-filled steel tubular (CFST) slender columns under axial and eccentric loads may undergo local and global interaction buckling when exposed to fire. Computational studies on the fire and post-fire behavior of rectangular short and slender CFST columns including local buckling effects have been extremely limited. This thesis presents new computational models for predicting the responses of rectangular and square CFST short and slender columns under fire exposure and after being exposed to fire. The models incorporate important features, which include local and global interaction buckling, air gap between the steel tube and concrete, concrete moisture content, emissivity of exposure surfaces, initial geometric imperfections, second-order, and material nonlinearities at elevated temperatures. Computational models are formulated by using the fiber approach for simulating the fire resistance, fire behavior and post-fire performance of rectangular CFST short and slender columns loaded concentrically and eccentrically. The progressive local buckling of steel tube walls at elevated temperatures is included in the formulation by using the local and post-local buckling models proposed. Computer simulation procedures sequentially coupling the nonlinear thermal and stress analyses are developed. The temperature distribution within a CFST column exposed to fire is determined by the thermal analysis. The modeling procedures capture the axial load-strain behavior, axial load-deflection responses, and fire-resistance of loaded CFST columns exposed to fire. Numerical solution algorithms implementing Muሷller’s method are developed to solve the nonlinear equilibrium equations of loaded CFST columns under fire exposure. The existing experimental and numerical results are utilized to validate the fiber-based computational models, which are employed to study the fire and post-fire responses of CFST short and slender columns with various important parameters. It is shown that the computational models are capable of predicting well the responses of rectangular CFST short and slender columns exposed to fire and after being exposed to fire. The computed results on the fires resistance and fire and post-fire behaviors of CFST rectangular columns with local buckling effects are given in the thesis for the first time. The research findings presented provide a better understanding of the fire and post-fire performance of short and slender CFST columns incorporating local buckling, and are valuable to structural designers and composite code writers.

Concrete filled steel tubular columns have been extensively used in modern construction owing to that they utilise the most favourable properties of both constituent materials. It has been recognized that concrete filled tubular columns provide excellent structural properties such as high load bearing capacity, ductility, large energy-absorption capacity and good structural fire behaviour. This paper presents the structural fire behaviour of a series of concrete filled steel tubular stub columns with four typical column sectional shapes in standard fire. The selected concrete filled steel tube stub columns are divided into three groups by equal section strength at ambient temperature, equal steel cross sectional areas and equal concrete core cross sectional areas. The temperature distribution, critical temperature and fire exposing time etc. of selected composite columns are extracted by numerical simulations using commercial FE package ABAQUS. Based on the analysis and comparison of typical parameters, the effect of column sectional shapes on member temperature distribution and structural fire behaviour are discussed. It shows concrete steel tubular column with circular section possesses the best structural fire behaviour, followed by columns with elliptical, square and rectangular sections. Based on this research study, a simplified equation for the design of concrete filled columns at elevated temperature is proposed.

Concrete is one of the most widely used materials within the construction industry due to its versatility, durability, superior mechanical properties and excellent resistance to fire. In addition to this, the rapid growth in population and urbanisation has accelerated the demand for high strength concretes. However, high strength concretes suffer a condition called spalling when exposed to elevated temperature levels which is associated with the breaking away or exploding of concrete layers due to the internal stresses. Additionally, concrete is a material having a very high carbon footprint mainly due to its binding material, cement, which is reported to be the second largest emitter of carbon dioxide. These issues have driven researchers to experiment alternative materials which can better benefit the economy and the environment. Studies show that blended concretes, which use supplementary cementitious materials such as slag, fly ash, silica fumes in partial replacement to cement and Geopolymer (GP) concretes, which eliminate cement usage altogether, display a high degree of resistance to fire. Additionally, these materials are further deemed worthy due the reduction or elimination of cement making it a more sustainable material. This study focuses on the fire performance of GP pastes, reactive powder concretes (RPC) and a newly developed GP paste based reactive powder concrete called reactive powder GP concrete (RPGC). RPGC was produced using class F fly ash and sodium-based activators in relation with silica fumes and micrometre aggregate. The study investigates properties such as workability, setting times, density, compressive strength, residual strength, thermal cracking and mass loss under controlled laboratory conditions. The study further investigates the performance of GP paste specimens of varied sizes subjected to different curing conditions. A comparison on the properties of two fly ash materials, namely Gladstone fly ash and Gladstone/Callide fly ash are also presented. Both types of fly ash displayed high early strengths and exceptional fire performance with a maximum strength gain of approximately 45% after an exposure to 400oC. RPC on the other hand exhibited high levels of explosive spalling at a temperature of around 360oC despite initial compressive strengths reaching a maximum of 140.7 MPa at 7-day testing. RPGC displayed good workability conditions with a maximum of 252 mm and a minimum of 187.5 mm, whilst achieving an initial compressive strength of 76.3 MPA at 24-hour testing. Furthermore, RPGC resulted in the lowest degree of thermal cracking with majority of the specimens having no visible cracking even after an exposure of 800oC. Moreover, RPGC recorded the lowest percentage mass loss amongst all experimented specimens.