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1
Renkas, A. A. "FIRE RESISTANCE PROVIDING OF HOLLOW‐CORE CONCRETE SLABS USING SHEET BUILDING MATERIALS." Fire Safety, no. 34 (July 19, 2019): 72–77. http://dx.doi.org/10.32447/20786662.34.2019.12.
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Introduction. This paper deals with the analysis of world experience in fire resistance providing of hollow‐core concrete slabs. To protect concrete structures are used many structural applications: thermal coatings and materials. The research first analyzes main methods and hypothesis using to make temperature analysis of solution fire resistance of concrete structures. Problem of making temperature analysis of hollow‐core concrete slabs are nonlinear thermal material properties and radiation heat transfer in the hollow-cores. The aim of this paper is to establish the temperature distribution in hollow‐core concrete slab considering radiation heat transfer in the hollow-cores in case of fire in compartment that is spreading by standard temperature-time curve. In addition, the aim is to substantiate the possibility of using gypsum panels to provide fire resistance of hollowcore concrete slabs. Material statement. The paper reports the results of modeling the process of heat transfer in hollow‐core concrete slab, between compartment space and slab surface and in hollow‐cores. To calculate temperature fields in hollow‐core concrete slab considering nonlinear thermal material properties and radiation heat transfer in the hollow-cores was used finite element model. At addition, the results of finite elements simulations show temperature fields in hollow‐core concrete slab and gypsum panels that installed under concrete slab. Scientific novelty. The paper reports results of theoretic substantiated of possibility of using gypsum panels to protect of hollow‐core concrete slabs considering nonlinear thermal material properties, radiation heat transfer between surfaces and radiation heat transfer in the hollow-cores. The results indicate that using gypsum panels to protect of hollow‐core concrete slabs reduces speed heating of concrete elements to critical temperatures that increase fire resistance of hollow‐core concrete slabs to 20.4 %.
2
Zhu, Desheng, Ji Ming Liu, and Zeng Wei Liu. "Properties of Profiled Steel Sheet-Concrete Structure under High-Temperature." Applied Mechanics and Materials 174-177 (May 2012): 113–16. http://dx.doi.org/10.4028/www.scientific.net/amm.174-177.113.
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Profiled steel sheet-concrete composite slab is a common structural elements in composite structure, mechanical properties in high temperature and thermal characteristics of the steel-concrete structure are the basis to analyzing structural response while in fire, bonding properties of profiled steel sheet and concrete play a key role in exerting the composite effect of steel and concrete in composite slabs.
3
Bellakehal, Hizia, Ali Zaidi, Radhouane Masmoudi, and Mohamed Bouhicha. "Combined effect of sustained load and freeze–thaw cycles on one-way concrete slabs reinforced with glass fibre – reinforced polymer." Canadian Journal of Civil Engineering 40, no. 11 (November 2013): 1060–67. http://dx.doi.org/10.1139/cjce-2012-0514.
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Flexural behaviour of reinforced-concrete slabs has been widely investigated to characterize properties and behaviour of fibre-reinforced polymer (FRP) materials as reinforcement for concrete structures. However, the short- and long-term thermal effects on FRP bars owing to the significant difference between the bars’ coefficients of thermal expansion in the transverse and longitudinal directions are still to be evaluated and may affect the bond properties and the concrete cover thickness after multiple exposures to freeze–thaw cycles. This paper presents the thermostructural behaviour of one-way concrete slabs reinforced with glass FRP (GFRP) that have previously been subjected to mechanical loads of 20% and 30% of the ultimate flexural capacity of reinforced-concrete slabs, simultaneously with short freeze–thaw cycles. Series tests were conducted on FRP-reinforced concrete slabs 500 mm wide, 195–215 mm thick, and 2500 mm long. The thermal cycles were varied from −30 to 60 °C. Four-point bending tests were conducted up to failure of the slabs. The results show that the thermomechanical load applied before bending tests increases the performance of reinforced-concrete slabs, particularly the concrete shear capacity. The deflection predicted from CSA code and ACI guidelines are very close to those obtained from experimental tests; however, the CSA code overestimates the deflection at the service load. The applied thermal cycles have no big influence on the behaviour before shear failure of concrete slabs reinforced with GFRP bars.
4
Nagy, Balázs, and Emese Paulik. "Reinforcement-Dependent Thermal Properties of Reinforced Concrete Columns and Slabs." Applied Mechanics and Materials 861 (December 2016): 279–86. http://dx.doi.org/10.4028/www.scientific.net/amm.861.279.
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Energy efficiency aspects are rarely considered during practical structural design. In building energetic calculations, thermal conductivity values from EN ISO 10456:2008 [1] are mainly used, although the standard define concrete’s values only by taking into account the density and the approximate percentage of reinforcement. Details of the structure type (column or slab), reinforcement (e.g. direction, diameter, amount of rebar spacers) and other properties (e.g. concrete composition) are not mentioned. In this research, we uncover the possible relations between the steel content parameters and thermal properties by laboratory measurements of 1:2 scaled reinforced concrete specimens and validated finite element models of columns and slabs with different designed reinforcements. Results shows, that depending on the structure type, design and steel content, there is a difference in the structure’s equivalent thermal conductivity. Our results and experiences of this research possibly can be used in energy conscious structural design practice.
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Martínez-Martínez, Juan Enrique, Felipe Pedro Álvarez-Rabanal, Mar Alonso-Martínez, and Juan José del Coz-Díaz. "Nonlinear Thermo-Structural Analysis of Lightweight Concrete and Steel Decking Composite Slabs under Fire Conditions: Numerical and Experimental Comparison." Applied Sciences 12, no. 18 (September 16, 2022): 9306. http://dx.doi.org/10.3390/app12189306.
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Composite slabs with steel decking profiles are widely used in building construction. However, the literature on the fire resistance of lightweight concrete (LWC) composite slabs with steel decking is limited. In this work, the thermo-structural performance of LWC composite slabs with trapezoidal steel decking was studied under fire conditions. A total of 12 experimental fire tests were carried out using specimens of 160 mm thickness, 1120 mm width and 2030 mm length, in which nine composite slabs were made of LWC and the remaining three slabs were made of normal concrete (NC) to serve as a benchmark for comparison. All the samples were tested in a furnace following EN 13381-5, applying the standardized time–temperature curve and constant load. During the experimental tests, phenomena such as the vaporization of the free water inside LWC, debonding between steel decking and concrete and changes in material properties affected the thermo-structural performance of composite slabs. The test results show that the load-bearing capacity of lighter slabs does not assure the minimum structural behavior of R30. However, the lighter the concrete is, the lower the thermal transmittance, improving the slabs’ thermal performance under fire conditions. Advanced nonlinear numerical models were developed to predict the thermal and structural performance of the studied LWC composite slabs in terms of temperature and time-displacement. The influences of key factors such as vaporization, thermal strains and debonding were included using material properties and a thermal contact conductance interlayer. Finally, the nonlinear models and the experimental results were compared. The difference between the experimental and numerical values was less than 15%, showing that the numerical results were in good agreement with the experimental results. The results of this study also compared the performance of LWC composite slabs with the NC composite slabs, giving rise to interesting conclusions from a practical point of view.
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Park, Hae-Won, Dong-Hyuk Kim, Cha-Sang Shim, and Jin-Hoon Jeong. "Behavior of Airport Concrete Pavement Slabs Exposed to Environmental Loadings." Applied Sciences 10, no. 7 (April 10, 2020): 2618. http://dx.doi.org/10.3390/app10072618.
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The behavior of pavement slabs was measured over a two-year period from the placement of concrete at a construction site in Incheon International Airport using temperature sensors and strain gauges. The influence of various environmental factors on the slab behavior was investigated by collecting weather data. Laboratory tests were conducted to obtain the material properties of the concrete slab, such as the elastic modulus, Poisson’s ratio, and modulus of rupture. The time of final setting of the concrete slab at the zero point of the strain gauges was determined according to the position and depth of the slab using the maturity of concrete obtained by a mortar penetration test. The real and shrinkage strains were calculated according to the position and depth of the slab using the coefficient of thermal expansion of the concrete, strain gauges, and correction factors of the strain gauges. The effects of environmental factors, such as temperature and moisture variations, were analyzed with respect to the strain in the concrete slab for the first seven days and two years after the placement of the concrete slab. The results obtained by the study shall be used to quantify the environmental effects on slabs for developing a method of designing airport concrete pavements.
7
Klemczak, Barbara. "Analytical Method for Predicting Early Age Thermal Effects in Thick Foundation Slabs." Materials 12, no. 22 (November 8, 2019): 3689. http://dx.doi.org/10.3390/ma12223689.
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Prediction of hydration temperature and induced stresses in mass foundation slabs, due to the hydration effects is a difficult task. The complexity of this issue is compounded by transient and non-linear thermo-mechanical phenomena as well by a significant number of contributing technological and material factors that affect the early-age volume changes. This is a probable reason for the limited number of simple analytical methods allowing for the estimation of these effects. This work presents a new proposal in the discussed field. The submitted analytical method for determining the hydration temperature rise, its differentials at a cross-section and induced thermal stresses in mass concrete foundation slabs considers the majority of important technological and material factors, such as the initial temperature of the concrete, the ambient temperature, the thermal properties of the concrete and the heat exchange conditions on the slab surfaces. In stress analysis, both self-balanced and restraint stresses are calculated. Finally, the method is validated in FE analysis conducted for the slabs with various heights and made of different types of cements, as well as by the thermal measurements from the construction site. Due to the limited number of methods allowing for the analytical estimation of the early age thermo-mechanical effects in slabs, this new proposal can be useful in the assessment of these effects.
8
Wang, Yabo, H. T. Liu, G. F. Dou, C. H. Xi, and L. Qian. "Experimental Study of Multi-Ribbed One-Way Composite Slabs Made of Steel Fibre, Foam, and Normal Concrete." Archives of Civil Engineering 64, no. 2 (December 31, 2018): 79–96. http://dx.doi.org/10.2478/ace-2018-0018.
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Abstract This paper aims to study the effect of reinforcement configuration (steel fibre and rebar) on the mechanical performance of composite slabs of the same total steel contents. We manufactured four pieces of fullscale multi-ribbed composite prefabricated slabs with different reinforcement configurations by using steel fibrereinforced concrete, foam concrete, and normal concrete. The multi-ribbed composite prefabricated slab has many excellent properties, such as light weight, good thermal and sound insulation. Thus, it can be applied to fabricated structures. In addition, the composite prefabricated slabs with the same total steel contents but with different reinforcement configurations were studied under the same static load, and many technical indicators such as crack resistance capacity, yield load, ultimate load capacity, maximum deflection, destructive pattern, and stress of steel rebar were obtained. Results indicate reinforcement configuration has a significant effect on the mechanical performance of composite prefabricated slabs with the same total steel contents, and composite prefabricated slabs reinforced with longitudinal rebar and steel fibre (volume fraction is 1.5%) have the best mechanical performance and ductility.
9
Son, Dong-Hee, Hyo-Jun Ahn, Joo-Hong Chung, Baek-Il Bae, and Chang-Sik Choi. "Deflection Estimation Based on the Thermal Characteristics of Composite Deck Slabs Containing Macro-Synthetic Fibers." Materials 14, no. 14 (July 20, 2021): 4052. http://dx.doi.org/10.3390/ma14144052.
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The purpose of this study was to evaluate the structural performance of composite deck slabs containing macro-synthetic fibers. after a fire by proposing a deflection estimation method for non-fireproof structural decks. Therefore, this study evaluated the fire resistance performance and deflection of deck slabs mixed with macro-synthetic fibers. Afterward, the deflection estimation method considering the thermal characteristics of concrete and deck plates was proposed. A material test was first conducted to evaluate the mechanical properties of concrete mixed with macro-synthetic fibers. This test found that the compressive strength and elasticity modulus of concrete mixed with macro-synthetic fibers was greater than that of general concrete. A flexural tensile test confirmed that residual strength was maintained after the maximum strength was achieved. The fire resistance of the deck slab was adequate even when a fire-resistant coating was not applied. The internal temperature was lowest for the specimen with macro-synthetic fibers. Deflection was evaluated using previously published equations and standards. The deflection evaluation confirmed that the temperature distribution should be applied differently in the estimation method that uses the thermal load of the deck slab.
10
Necib, Hichem, Djamel Belatrache, Hafnaoui Goutar, and Nesrine Sahraoui. "Experimental Study of Thermal Conductivity of Concrete with Biosourced Material for Saved Energy in Buildings." Annals of West University of Timisoara - Physics 64, no. 1 (November 28, 2022): 158–71. http://dx.doi.org/10.2478/awutp-2022-0011.
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Abstract This study aims to improve the thermal efficiency of concrete slabs by introducing a plant material. This can contribute to the improvement of internal thermal comfort for buildings and this by lower energy consumption. For this, several experiments were carried out at the laboratory, to find the thermal properties of a new innovative building material produced by inserting ALFA (STIPA TENACISSIMA) into a concrete slab. Several mass percentages of ALFA relative to the total mass of the concrete slab (0%, 0.4%, 0.8%, 1.2% and 1.6%) were studied to see the effect of the introduced quantity of this plant on the thermal conductivity of concrete. It was concluded that the insertion of ALFA in the concrete, decreases considerably the thermal conductivity. The best results are noticed for 1.2% of ALFA, whose thermal conductivity of the concrete is reduced up to 50.61%. As a result, heat gains and losses, through wall or slab, are significantly reduced, which reduces the energy consumed by cooling and heating of homes. In addition, the degree-day method was used to calculate the costs of cooling and heating energy for 58 regions in Algeria. The lowest total energy cost is noticed in the TENES region, while the highest energy cost is noticed in the BORDJ B. MOKHTAR region.
11
Mohammad Jani, Noraniza, Mohammad Shakir Nasif, Nasir Shafiq, and Ian Holt. "Experimental Investigation on the Effect of Varying Fiber Mix Proportion on the Mechanical and Thermal Performances of Fiber-Reinforced Self-Compacting Concrete under Hydrocarbon Fire Condition." Applied Sciences 10, no. 13 (July 2, 2020): 4586. http://dx.doi.org/10.3390/app10134586.
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This paper presents the experimental analysis of the effects of simulated hydrocarbon fire exposure on the mechanical properties and the heat transmission in fiber-reinforced self-compacting concrete, FR-SCC. For that purpose, 300-mm thick, and 1200-mm square-shaped slabs were cast. Basalt and polyvinyl alcohol (PVA) fibers were added using the content of 1, 1.5, and 2% in self-compacting concrete. For investigating the heat transmission within 300-mm thick slabs, five external thermocouples were installed at the unexposed face to the fire of the slabs. Similarly, eleven internal thermocouples were installed at an interval of 25 mm throughout the slab thickness. It has been found that fibers have shown better insulation than the controlled concrete; the unexposed to fire surface of FR-SCC showed temperatures lower by ten degree Celcius than the controlled concrete. Compressive strength results showed that fiber addition caused a higher reduction in strength because of softening and stiffness reduction due to high-temperature exposure. After 120 min of fire exposure, basalt fibers caused an average reduction of 30% in the compressive strength, and PVA fibers caused an average reduction of 25%. Whereas, the addition of fibers improved the split cylindrical tensile strength even after exposure to 120 min of fire exposure in comparison with the unreinforced samples.
12
Mateos, Angel, John Harvey, Dulce Rufino Feldman, Rongzong Wu, Julio Paniagua, and Fabian Paniagua. "Evaluation of the Moisture Dependence of Concrete Coefficient of Thermal Expansion and Its Impacts on Thermal Deformations and Stresses of Concrete Pavements." Transportation Research Record: Journal of the Transportation Research Board 2674, no. 8 (June 27, 2020): 545–55. http://dx.doi.org/10.1177/0361198120925463.
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The coefficient of thermal expansion (CTE) is one of the material properties of concrete that has the largest impact on rigid pavement performance. Concrete CTE is typically measured in the laboratory, under saturated conditions, or estimated on the basis of the mix constituents, past experience, or both. Whichever method is used, the mechanistic-empirical design of concrete pavements traditionally assumes a constant value for this material property. This assumption has important consequences in relation to predicting thermal deformations and stresses since the CTE of concrete actually changes with the concrete’s internal moisture conditions. The experimental data presented in this study show that this assumption, together with the way CTE is measured in the laboratory, leads to systematic underestimates of thermal deformations and stresses in concrete pavements. The experimental data come from six concrete overlays of asphalt pavements that were instrumented with thermocouples, relative humidity sensors, and vibrating wire strain gauges to measure the expansion/contraction and bending of the slabs because of temperature and moisture-related actions. The apparent CTE of the overlay slabs reached values up to 65% larger than the CTE measured in the laboratory under saturated conditions. Using finite element method modeling, it was determined that thermal stresses were up to 70% larger than predicted using the saturated CTE.
13
Zhang, Huanqing, Zheng Zhang, Helong Wu, Sritawat Kitipornchai, Guozhong Chai, and Jie Yang. "Thermal Buckling and Postbuckling Analysis of Functionally Graded Concrete Slabs with Initial Imperfections." International Journal of Structural Stability and Dynamics 18, no. 11 (October 22, 2018): 1850142. http://dx.doi.org/10.1142/s0219455418501420.
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This paper proposes a novel functionally graded (FG) concrete slab and investigates its thermal buckling and postbuckling performance using the finite-element (FE) method. The concrete slab consists of three homogeneous thick layers — a fiber-reinforced concrete layer, a geopolymer concrete layer, and a plain Portland cement (PPC) layer — with a thin FG layer between the thick layers. The mechanical properties of the thin FG layers are exponentially graded across the thickness direction. The effects of initial imperfection, the self-weight of the slab, and the friction between the slab and rigid foundation are considered in the analysis. The FE model is validated against the results reported in the literature. A comprehensive parametric study is conducted to examine the effects of the thickness and volume fraction index of the FG layer, initial imperfection, self-weight, friction, and slab slenderness ratio on the thermal buckling and postbuckling behaviors of the concrete slab. The numerical results demonstrate that the proposed FG slab exhibits remarkably better buckling and postbuckling resistance than a conventional PPC concrete slab and that the influences of both self-weight and friction are important and cannot be neglected.
14
Millers, Renars, Aleksandrs Korjakins, and Arturs Lesinskis. "Thermally Activated Concrete Slabs with Integrated PCM Materials." E3S Web of Conferences 111 (2019): 01080. http://dx.doi.org/10.1051/e3sconf/201911101080.
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As building codes are pushing towards higher energy efficiency and the arrival of nearly Zero Energy Building (nZEB) requirements for all new buildings are just around the corner the need for alternative, high efficiency heating and cooling solutions for nZEB’s is greater than ever. Also as experience with renewable energy sources has proven the energy demand and energy generation rarely overlaps and it does not allow to fully utilise some renewable energy sources. This is a simulation study that focuses on integrated cooling and energy storage system utilising phase-change materials (PCM). Several types of thermally activated slabs with different PCM thicknesses were simulated in order to find the most optimal PCM thickness with melting point temperature that can support passive cooling methods based on adiabatic cooling principles. Two calculation tools were used for the study – IDA ICE 4.8 and U-NORM 2012-2 to calculate the properties of the slabs and potential of application in well insulated residential building in Baltic climate. The results showed that the optimal thickness for thermally activated PCM layer (large flat containers) range from 25 mm to 90 mm, and for layers with no thermal activation – 180 mm and more. Moreover the results show that apart from energy storage the thermally activated panel can increase thermal comfort conditions.
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Linek, Małgorzata. "Application of ceramic dust as a modifier reducing the extent of rheological deformations in airfield pavement concrete." MATEC Web of Conferences 163 (2018): 03007. http://dx.doi.org/10.1051/matecconf/201816303007.
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The article presents material solution based on the application of ceramic dust as concrete mix component intended for airfield pavements. Material composition is intended for the application on the selected areas of pavement exposed to the influence of imposed thermal loads intensifying the stress strain state of concrete slabs. Due to the nature of loading of these parts it is necessary to reduce the extent of registered rheological deformations. Concrete containing dust additive is distinguished by more favourable porosity properties, more consistent cement matrix without visible discontinuities and with the formed different hydration products. Diversification of internal micro structure of cement concrete using the suggested dust has significant influence on the improvement of mechanical, physical and performance parameters. Also, assessment of the applied dust influence on the extent of the registered rheological deformations was presented. The analyses included concretes curing in standard conditions and concretes subject to thermal cycles representing the destructive influence of imposed loading. The obtained laboratory test results prove clearly the validity of the suggested solution. Reducing the extent of deformations is derivative of favourable changes observed in internal structure of concrete composite. Better formed contact areas provide the increased concrete parameters and consequently influence extending concrete durability.
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Heiza, Khaled, Fatma Eid, and Taha Masoud. "Lightweight self-compacting concrete with light expanded clay aggregate (LECA)." MATEC Web of Conferences 162 (2018): 02031. http://dx.doi.org/10.1051/matecconf/201816202031.
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Lightweight concretes have been successfully applied in building constructions for many years due to their favorable material properties, particularly their low specific weight in connection with a high strength, a high capability of thermal insulation and a high durability. The development leading to lightweight self-compacting concrete (LWSCC) represents an important advanced step within the recent years. This concrete combines the favorable properties of a lightweight concrete with those of a self-compacting concrete. Research work is aimed on development of (LWSCC) with the use of light aggregates “Light expanded clay aggregate (LECA)”. In this research, first by specific gravity factor method, twenty different mix designs of (LWSCC) were cast and tested to find out the values of slump flow, J-ring , V-funnel and 28 day compressive strength. Based on the results obtained, the best mix design was selected for further investigation. This paper also focuses on studying the effect of changing the reinforcement ratio on reinforced two way slabs when the dimensions were kept constant.
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Florian, Aleš, Lenka Ševelová, and Jaroslav Žák. "Reliability Analysis of Temperature Influence on Stresses in Rigid Pavement Made from Recycled Materials." Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 64, no. 2 (2016): 423–32. http://dx.doi.org/10.11118/actaun201664020423.
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Complex statistical and sensitivity analysis of principal stresses in concrete slabs of the real type of rigid pavement made from recycled materials is performed. The pavement is dominantly loaded by the temperature field acting on the upper and lower surface of concrete slabs. The computational model of the pavement is designed as a spatial (3D) model, is based on a nonlinear variant of the finite element method that respects the structural nonlinearity, enables to model different arrangement of joints, and the entire model can be loaded by thermal load. Four concrete slabs separated by transverse and longitudinal joints and the additional structural layers including soil to the depth of about 3 m are modeled. The thickness of individual layers, physical and mechanical properties of materials, characteristics of joints, and the temperature of the upper and lower surface of slabs are supposed to be random variables. The simulation technique Updated Latin Hypercube Sampling with 20 simulations is used for the reliability analysis. As results of statistical analysis, the estimates of basic statistics of the principal stresses σ1 and σ3 in 106 points on the upper and lower surface of slabs are obtained. For sensitivity analysis the sensitivity coefficient based on the Spearman rank correlation coefficient is used. As results of sensitivity analysis, the estimates of influence of random variability of individual input variables on the random variability of principal stresses σ1 and σ3 are obtained.
18
Gharbi, Athraa H., and Akram S. Mahmoud. "Punching Shear Behavior of Reinforced Concrete Slabs under Fire using Finite Elements." Journal of Engineering 26, no. 5 (May 1, 2020): 106–27. http://dx.doi.org/10.31026/j.eng.2020.05.08.
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The main aim of this paper is studied the punching shear and behavior of reinforced concrete slabs exposed to fires, the possibility of punching shear failure occurred as a result of the fires and their inability to withstand the loads. Simulation by finite element analysis is made to predict the type of failure, distribution temperature through the thickness of the slabs, deformation and punching strength. Nonlinear finite element transient thermal-structural analysis at fire conditions are analyzed by ANSYS package. The validity of the modeling is performed for the mechanical and thermal properties of materials from earlier works from literature to decrease the uncertainties in data used in the analysis. A parametric study was adopted in this study, it has many factors such as the ratios of length to thickness, fire temperature, time exposed to fire, concrete compressive strength, area exposed to fires and type of support. It can be concluded from this research the significant factors that affect the punching shear strength. However, the increasing ratio of length to thickness may be lead to increasing the deflection more than 123% at fire condition. Also, the increasing temperature leads to increasing the deflection about 40% at fire condition.
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Yu, Xin Meng, Xiao Xiong Zha, and Zhao Hui Huang. "The Influence of Spalling on the Fire Resistance of RC Structures." Advanced Materials Research 255-260 (May 2011): 519–23. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.519.
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A great many of experiments has shown that reinforced concrete (RC) structures suffered from spalling in fire. However, at present there are still no convincing spalling predicting models available due to the inhomogeneous nature and complicated thermo-hydro-mechanical interactions in concrete at elevated temperatures. In order to evaluate the fire resistance of RC structures which are subjected to concrete spalling, a thermal analysis procedure is developed which considers the effects of spalling on the growth of temperature in RC members. The predicted temperatures are then used to model the structural behaviour. The spalled portion of concrete is modelled as "void", which has no thermal and mechanical properties. A series of parametric studies carried out on RC structural members with different boundary conditions shows that the influence of spalling on fire resistance is very significant apart from the RC slabs subject to higher laterally restraint.
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HLADYSHEV, Hennadii, and Dmytro HLADYSHEV. "DETERMINATION OF THE ZONE OF THERMAL INFLUENCE OF FIRE BY RESULTS INSPECTION OF FLOOR STRUCTURES." Building constructions. Theory and Practice, no. 10 (June 27, 2022): 32–41. http://dx.doi.org/10.32347/2522-4182.10.2022.32-41.
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The results of the study of the technical condition of 14 round-hollow slabs according to the series II-03-02 within the basement of two entrances of a residential building after a fire, lasting about 8 hours. More than 40 years passed from the commissioning of the building to the fire, and all this time the basement slabs were in a non-aggressive environment, but with high relative humidity, which had a positive effect on increasing the concrete strength of typical slabs. Inspection of slabs in adjacent rooms for a long time of operation did not reveal significant defects from their humidification and insufficient thermal insulation properties of the floor above the basement.
In the inspection area, some floor slabs above the basement were found to be defective due to high temperatures, which reduced their rigidity.
The information obtained from the survey is necessary to perform verification calculations to determine the load-bearing capacity and stiffness of the floor slabs and compare them with the data from the survey results. The data of test calculations are also needed to substantiate the need for reinforcement work on the slabs, to ensure their further normal operation on the operating loads on the ground floor.
To analyze the impact on the deflections of slabs of constant and payloads, some of their actions are considered and verified calculations of the deflections of the floor slabs for the four adopted separate stable modes of normal operation.
A histogram of the change in the actual deflections of the floor slabs above the basement is constructed, according to the analysis of which the area with the largest deflections is clearly traced, which indicates the location of the highest temperatures in this place. That is, the level of vertical deformations of floor slabs can determine the relative temperature distribution within them. Deflections of slabs due to high temperatures should be considered as damage that interferes with normal operation and significantly reduces the durability of slabs.
Considered after the fire condition of the slabs showed that in the absence of impact on them payloads, the obtained additional temperature deflections are greater than the calculated, which are obtained by verification calculations for the action of full operating loads.
Also offered different options for strengthening both the slabs themselves and the seams between them, for their joint work on different combinations of loads.
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Klemczak, Barbara, Maciej Batog, Zbigniew Giergiczny, and Aneta Żmij. "Complex Effect of Concrete Composition on the Thermo-Mechanical Behaviour of Mass Concrete." Materials 11, no. 11 (November 7, 2018): 2207. http://dx.doi.org/10.3390/ma11112207.
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The current work presents the complex investigation of the influence of cement and aggregate type on the thermo-mechanical behavior of mass concrete. Six types of cement with different amounts of non-clinker constituents and four types of aggregates are used in experimental tests. Particular attention was given to the low clinker cements with high amounts of siliceous fly ash and ground blast furnace slag. The experimental research covered the determination of thermal, mechanical, and rheological properties of early age concrete with different constituents. Experimental results have been used both to validate the numerical model and analysis of exemplary foundation slab. The results confirm the importance of the concrete mix composition and it has been shown that the early-age volume deformation and possible cracking is the result of the concerted action of thermal and mechanical properties of concrete. The obtained results indicate granite as the best aggregate for mass concrete. Considering the type of cement, much better behaviour of mass concrete has been noted for cements with fly ash and composite cements containing both fly ash and slags than cements only with slag.
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Jiang, Ying Bo, and Xiao Rong Wang. "Research on Thermal and Structural Performances of Shale Ceramsite Concrete." Advanced Materials Research 168-170 (December 2010): 885–88. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.885.
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Shale ceramsite concrete is a kind of materia with lightweight, heat preservation, heat insulation, fire resistance, earthquake resistance and other excellent performances as green building materials, it has very broad application prospects. Its consumption in China is second only to the density of ordinary concrete. In this paper, local shale products, by ordinary concrete slab and shale concrete slab structure comparison of performance tests and the thermal performance test, indicating shale properties of concrete.
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Nishizawa, Tatsuo, Shigeru Shimeno, Akinori Komatsubara, and Masashi Koyanagawa. "Temperature Gradient of Concrete Pavement Slab Overlaid with Asphalt Surface Course." Transportation Research Record: Journal of the Transportation Research Board 1730, no. 1 (January 2000): 25–33. http://dx.doi.org/10.3141/1730-04.
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In the structural design of composite pavement with a concrete pavement slab overlaid with an asphalt surface course, it is very important to estimate the temperature gradient in the concrete slab. An asphalt surface course reduces the temperature gradient in an underlaid concrete slab, resulting in the reduction of thermal stress of the concrete slab. This effect was investigated by temperature measurement in model pavements and by thermal conductivity analysis. Thermal properties were estimated by a backanalysis by using measured temperatures over 1 year. From the numerical simulations varying the thickness of asphalt surface and concrete slab, the relationship between the reduction effect and the asphalt thickness was derived as a function of the thickness of asphalt surface course, which can be used in the structural design of the composite pavement.
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Szymczak-Graczyk, Anna. "Numerical Analysis of the Impact of Thermal Spray Insulation Solutions on Floor Loading." Applied Sciences 10, no. 3 (February 4, 2020): 1016. http://dx.doi.org/10.3390/app10031016.
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The paper presents the effect of considering the substrate under the floor—insulation in the form of closed-cell polyurethane spray foam, which is used for insulating surfaces particularly exposed to mechanical impact. The layer of thermal insulation was made by spraying, which prevents the occurrence of thermal bridges due to tight filling of the insulated space. It seems extremely important to adopt the appropriate material characteristics of an insulating layer. The basic thermophysical properties of polyurethane foam justifying its choice as an insulation material were the values of its thermal conductivity coefficient (0.022 W/(mK)) and density (36 kg/m3). However, what was the most important for the calculations provided in the work was to determine the stiffness of the foam subgrade so as to assess its impact on the floor load capacity. The paper includes calculations for a floor slab characterized by a static diagram, with all edges free (unfixed), loaded in strips circumferentially. The reinforced concrete slab was 6 × 6 m long, 0.25 m thick, and made of C20/25 concrete resting on an elastic substrate. Calculations were made for two variants taking into consideration two values of subgrade stiffness. The first variant concerned the subgrade stiffness for sprayed polyurethane foam insulation. On the basis of laboratory tests in situ made according to the standard procedure, its average value was assumed as K = 32,000 kN/m3. The second, comparative, computational variant included the subgrade stiffness equal to K = 50,000 kN/m3. A variation approach to the finite difference method was used for static calculations, adopting the condition for the minimum energy of elastic deformation while undergoing bending that was accumulated in the slab resting on a Winkler elastic substrate. Static calculations resulted in obtaining the values of deflections at each point of the discretization grid adopted for the slab. The obtained results have proved the necessity of calculating the floor as a layer element. For the reference substrate with the subgrade stiffness K = 50,000 kN/m3 that was adopted in the work, the value of the bending moment was 17% lower than when taking into account that there was thermal insulation under the floor slab, causing an increase in the deflection of the slab and an increase in its bending moment. If a design does not include the actual subgrade stiffness of the layer under the floor slab, it results in an understatement of the values of the bending moments on the basis of which the slab reinforcement is designed. Adherence of insufficient concrete slab reinforcement may cause subsequent damage to floor slabs.
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Rodríguez, Carlos, Isidro Sánchez, Isabel Miñano, Francisco Benito, Marta Cabeza, and Carlos Parra. "On the Possibility of Using Recycled Mixed Aggregates and GICC Thermal Plant Wastes in Non-Structural Concrete Elements." Sustainability 11, no. 3 (January 25, 2019): 633. http://dx.doi.org/10.3390/su11030633.
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Industrial wastes are often used as aggregate in concrete production to promote a more sustainable construction and to reduce production costs. This article presents the results of an experimental campaign on the influence of replacing natural aggregate with several construction and demolition wastes (C&DW) as recycled aggregate, as well as the use of fly ash and slag, wastes produced in Gas Incinerator Combined Cycle (GICC) thermal power plants, in the mix design of non-structural concrete. Different percentages of natural aggregates were substituted with recycled aggregates either coming from construction and demolition wastes, or from the coarse fraction of the slags from thermic plants in the manufacture of concrete. The mechanical properties, capillary water absorption, density, carbonation, chloride ingress and sulphate resistance have been tested. The results show a decrease in properties when C&DW are used. Fine fraction of slag and fly ash has an important advantage, and can even improve the long term properties of concrete prepared with natural aggregates. Coarse fraction of slag as a recycled aggregate generally improves most of the properties of manufactured concretes.
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Dovzhenko, O. A., V. V. Pohribnyi, and L. V. Karabash. "EFFECTIVE KEYED CONNECTIONS OF HOLLOW-CORE FLOOR SLABS WITH WALLS IN MODERN LARGE-PANEL HOUSE BUILDING." Science & Technique 17, no. 2 (April 13, 2018): 146–56. http://dx.doi.org/10.21122/2227-1031-2018-17-2-146-156.
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The paper considers large-panel constructive system of multi-storey buildings and its industrial basis creates conditions for intensive volume growth in house construction. Application of hollow-core panels are recommended as floor slabs that allows to increase a distance between bearing walls, to improve planning solutions, and also significantly to increase thermal and sound protection properties of floor discs (coatings). Keyed joints having the highest resistance to shearing forces are used to ensure joint action of the slabs with wall panels. A supporting unit of floor elements in the precast-monolithic constructive system ARKOS by means of concrete keys is considered as a prototype of the considered joint. In order to increase a bearing capacity and improve reliability of joints it is envisaged to reinforce keys with space frames. Improvement of joint units is possible to carry out with due account of total number of the factors influencing on strength. Poltava National Technical University named after Yuri Kondratyuk has developed a general methodology for assessment of bearing capacity in keyed joints which is based on the variational method in the theory of concrete plasticity and reflects specificity of stress-strain state of the failure zone. For experimental verification of this methodology investigations have been carried out with the purpose to test operation of keys when they are reinforced in mid-height and reinforcement is distributed in two tiers. The observed experimental fracture pattern in the specimens has confirmed kinematic schemes accepted for calculations and comparative analysis of experimental and theoretical values points to their closeness. Two-level reinforcement significantly improves plastic properties of concrete keys and excludes brittle failure. The proposed design of the joint unit for floor slabs with wall panels is characterized by the ratio of key dimensions and shape of reinforcing cages in the form of hollow cylinders which ensure higher strength and seismic resistance of a joint.
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Alyousef, Rayed, Omrane Benjeddou, Chokri Soussi, Mohamed Amine Khadimallah, and Malek Jedidi. "Experimental Study of New Insulation Lightweight Concrete Block Floor Based on Perlite Aggregate, Natural Sand, and Sand Obtained from Marble Waste." Advances in Materials Science and Engineering 2019 (March 3, 2019): 1–14. http://dx.doi.org/10.1155/2019/8160461.
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The purpose of the present study is to recover marble waste and expanded perlite aggregate (EPA) for use as an additive to cementitious matrix building materials. The main goal is to produce a new insulation block floor from lightweight concrete (LC) by mixing sand from the waste marble crushing process (SWM), natural sand, and EPA. First, optimal mixture of natural sand, SWM, and EPA was determined for a given insulation LC. To this end, plate and cubic specimens were prepared by varying the volume proportion of SWM to natural sand in percentages of 0, 20, 40, 60, 80, and 100. Mechanical and physical properties such as the compressive strength, thermal conductivity, thermal diffusivity, specific heat capacity, and sound reduction index at different frequencies were investigated. Finally, a prototype of a new insulation lightweight block floor was manufactured from the optimal mixture of the studied LC. The results showed that the incorporation of SWM significantly improved the mechanical properties and the thermal insulation of LC compared to those of the natural sand. These results are promising and give the present insulation block floor the opportunity to be used in composite slabs.
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Huang, Jiang, Dong Hao Lou, Hong Qiang Fang, and Yuan Cheng. "Study on Thermal Stresses of Over-Long Concrete Slab." Applied Mechanics and Materials 188 (June 2012): 150–56. http://dx.doi.org/10.4028/www.scientific.net/amm.188.150.
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Based on available theories and practical experience, this paper present an analytical method used for analyzing thermal stresses of over-long concrete slab through design for a real typical structure. Construction sequence, temperature conditions and material properties were considered. It stated that overlong non-joint structures exceeding code limits could be adopted according to the result from the structural analysis.
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Davids, William G. "Foundation Modeling for Jointed Concrete Pavements." Transportation Research Record: Journal of the Transportation Research Board 1730, no. 1 (January 2000): 34–42. http://dx.doi.org/10.3141/1730-05.
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Issues related to the finite element modeling of base and subgrade materials under jointed plain concrete pavements are examined. The threedimensional finite element program EverFE, developed in conjunction with the Washington State Department of Transportation, was employed for the analyses. The relevant modeling capabilities of EverFE are detailed, including the ability to model multiple foundation layers, the incorporation of loss of contact between slab and base, and the efficient iterative solution strategies that make large three-dimensional finite element analyses possible on desktop computers. The results of parametric studies examining the effects of foundation type (layered elastic and dense liquid) and properties on the response of jointed plain concrete pavements subjected to axle and thermal loads are presented. Special attention is paid to the interactions between joint load transfer effectiveness and foundation type, and joint load transfer is shown to change significantly with different foundation models and properties. A consideration of simultaneous thermal and axle loadings indicates that the effect of foundation type and properties on critical slab stresses caused by edge loading and a positive temperature gradient is relatively small. However, the slab response is quite sensitive to foundation type for a combined negative temperature gradient and corner loading. On the basis of these results, use of an equivalent dense liquid foundation modulus in mechanistic rigid pavement analysis or design is not recommended when stiff base layers are present.
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Chen, Dai Guo, Yong Yao, Hai Jun Wang, Yu Ping Zhu, and Jiao Li Zou. "Experiment Research on Thermal Performance of Foam Concrete Wall." Applied Mechanics and Materials 488-489 (January 2014): 609–13. http://dx.doi.org/10.4028/www.scientific.net/amm.488-489.609.
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Foam concrete is a new building energy-saving material, which has the characteristics of light weight, heat insulation and fire prevention. The use of foam concrete slab with grooves cast roof or wall as a template can reduce the amount of the construction process, the cost of project and improve the structural thermal insulation properties. By testing the thermal defects and heat transfer performance of outer insulation and self-insulated wall, and analysis 2 kinds of wall’s heat transfer coefficient, thermal inertia indicators and technical and economic characteristics with Building Heat Transfer Theory, obtain : Foam concrete self thermal insulation wall indoor a hot environment, thermal stability and resistance against external temperature fluctuations is stronger; foam concrete self thermal insulation wall have a good heat transfer performance, and have better marketing prospects.
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Yehia, Sherif A., and Christopher Y. Tuan. "Thin Conductive Concrete Overlay for Bridge Deck Deicing and Anti-Icing." Transportation Research Record: Journal of the Transportation Research Board 1698, no. 1 (January 2000): 45–53. http://dx.doi.org/10.3141/1698-07.
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Concrete bridge decks are prone to ice accumulation. Bridge decks freeze before the roads approaching them freeze, making wintry highway travel treacherous. Road salts and deicing chemicals are effective for ice removal but cause damage to concrete and corrosion of reinforcing steel in concrete bridge decks. The resulting rapid degradation of existing concrete pavements and bridge decks is a major concern to transportation and public-works officials. The use of insulation materials for ice control and electric or thermal heating for deicing have been attempted, with unsatisfactory results. Conductive concrete is a cementitious admixture containing electrically conductive components to attain high and stable electrical conductivity. Due to its electrical resistance and impedance, a thin conductive concrete overlay can generate enough heat to prevent ice formation on a bridge deck when connected to a power source. In 1998, Yehia and Tuan, at the University of Nebraska–Lincoln, developed a conductive concrete mix specifically for bridge deck deicing. In this application, a conductive concrete overlay is cast on the top of a bridge deck for deicing or anti-icing. The mechanical and physical properties of the conductive concrete mix after 28 days have met ASTM and AASHTO specifications. Two concrete slabs were constructed with a 9-cm (3.5-in.) conductive concrete overlay for conducting deicing experiments in the natural environment. Deicing and anti-icing experiments were conducted in five 1998 snowstorms. Average power of about 590 W/m2 (55 W/ft2) was generated by the conductive concrete overlays to prevent snow and ice accumulation.
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Bertagnoli, Gabriele, Dario La Mazza, Giuseppe Mancini, and Francesco Tondolo. "Design of Massive Casting Controlling Early Age Properties of Concrete." Key Engineering Materials 711 (September 2016): 126–33. http://dx.doi.org/10.4028/www.scientific.net/kem.711.126.
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The design of concrete structures exposed to environmental attack requires serious attention for concrete durability. Early age cracking due to autogenous deformations should be avoided.In this work the study of the structural effects of hydration heat and rheological behaviour of a massive concrete casting is presented. The object of the study is a skyscraper foundation slab. Aim of the work is the numerical simulation of what occurs to the structure during the hardening, in order to avoid unforeseen autogenous cracking and therefore the choice of a tailor-made concrete mixture able to fulfil the performance criteria.Non-linear finite element coupled thermal and mechanical analyses have been performed taking into account: hydration heat generation and dispersion, dimension and sequence of the casting, evolution of concrete mechanical properties in time during the hardening reaction, creep and differential shrinkage.
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Pancar, Erhan Burak. "Using Recycled Glass and Zeolite in Concrete Pavement to Mitigate Heat Island and Reduce Thermal Cracks." Advances in Materials Science and Engineering 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/8526354.
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Urban heat island (UHI) effect is built environmental issue related to pavements. It is desired to reduce pavement high surface temperature in summer to mitigate UHI effect. High surface temperature also affects slab temperature difference (the top surface temperature minus the bottom surface temperature of the slab). The increased slab temperature difference induces a high possibility of cracking in concrete roads. The prime aim of this study was to reduce the slab surface temperature by using recycled glass as a fine aggregate and zeolite as cement in concrete. Recycled glass was used to replace fine aggregate in proportions of 10%, 20%, and 30% by total weight of aggregate. Zeolite replaced Portland cement in proportions of 10% and 30% for three different proportions of recycled glass concrete mixtures. Optimum proportions were determined by examining mechanical properties of samples and alkali-silica reactions. It was noticed that using recycled glass and zeolite together in concrete reduces pavement surface temperature and temperature gradient in summer.
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Papadimitriou, Christina, Lazaros Melidis, Lambros Kotoulas, Nikolaos Makris, and Konstantinos Katakalos. "Thermomechanical Characterization of CFRPs under Elevated Temperatures for Strengthening Existing Structures." Fibers 9, no. 12 (December 3, 2021): 80. http://dx.doi.org/10.3390/fib9120080.
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Fiber-reinforced polymers (FRP) are rapidly gaining acceptance from the construction sector due to their large effectiveness. They are mainly used as confining reinforcement for concrete columns and as tensile reinforcement for concrete beams, columns and slabs. FRPs are already used to a large extent for applications such as bridges and parking lots, where elevated temperatures are not the main risk. Their increasing use as structural reinforcement is hampered by the concern related to their behavior at elevated temperatures as the relevant research is deficient. Thanks to the significant advantage of FRPs’ mechanical properties, further investigation into the influence of heating on their mechanical behavior may solve many doubts. The present study examines the influence of temperatures, ranging among 50, 100 and 250 °C, on the tensile strength of FRP laminates with carbon fibers (CFRP). In addition, the resistance of CFRP specimens to low-cycle thermal loading at the temperatures of 50, 100 and 250 °C under constant tensile load was investigated. The experiments were carried out in the laboratory of Experimental Strength of Materials and Structures of Aristotle University of Thessaloniki.
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Xie, Pengyu, and Hao Wang. "Analysis of Temperature Variation and Thermally-Induced Reflective Cracking Potential in Composite Pavements." Transportation Research Record: Journal of the Transportation Research Board 2674, no. 10 (August 17, 2020): 177–88. http://dx.doi.org/10.1177/0361198120941848.
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Reflective cracking is the major distress in composite pavement and can accelerate the deterioration of the whole structure. This paper analyzes the potential for reflective cracking in composite pavements because of thermal cycles. A heat transfer model was first developed to predict cyclic temperature variations with climatic inputs (solar radiation, wind velocity, air temperature, and humidity). Mechanical models were then employed to analyze thermally-induced reflective cracking potential using fracture mechanics parameters. Both models were validated through field measurement of temperature profile and crack propagation. The temperature profile in composite pavement can be predicted accurately from climate data and typical thermal material properties. Because of the temperature variation and gradient in composite pavement, concrete slabs undergo joint opening and curling deformation and stress concentration occurs at the bottom of the overlay. The loading cycles for initiation and propagation of reflective cracking were predicted by empirical equation and Paris’ law. Increasing overlay thickness can extend the pavement service life, but care is needed as different thicknesses offer varying efficiency. Thicker asphalt overlay mitigates reflective crack potential, especially at the crack initiation phase.
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Achenbach, Marcus, Tom Lahmer, and Guido Morgenthal. "Identification of the thermal properties of concrete for the temperature calculation of concrete slabs and columns subjected to a standard fire—Methodology and proposal for simplified formulations." Fire Safety Journal 87 (January 2017): 80–86. http://dx.doi.org/10.1016/j.firesaf.2016.12.003.
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Starcev, Vladimir, S. Nikolenko, and Svetlana Sazonova. "MODELING THE THERMAL STRESS STATE OF THE FOUNDATION AND DEVELOPMENT OF MEASURES." Modeling of systems and processes 13, no. 2 (September 21, 2020): 64–71. http://dx.doi.org/10.12737/2219-0767-2020-13-2-64-71.
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The modeling of the thermal stress state of the foundation slab of the building of a general educational institution is considered. The performed calculations took into account the occurrence of stresses as a result of heating of the concrete mass during cement hydration. To simulate the thermal stress state, the specialized Midas Fea software package is used. At control points, diagrams of changes in temperatures, stresses, and crack formation coefficients depending on the periods of curing are obtained. The isopoles of temperature distribution and crack formation coefficients over the volume of the studied array were obtained. Measures have been developed to improve the operational properties of concrete, including engineering and technical recommendations to reduce the negative impact of temperature differences on the manufacturing process of concrete mixtures and foundations.
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Onyshchenko, Artur, and Volodymyr Zelenovskyi. "EVALUATION OF EPOXY-BITUMEN COMPOSITE FOR ITS APPLICATION IN ASPHALT CONCRETE THIN-LAYER COATINGS ON HIGHWAY BRIDGES." Dorogi i mosti 2022, no. 26 (October 3, 2022): 172–82. http://dx.doi.org/10.36100/dorogimosti2022.26.172.
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Introduction. In this review, epoxy components, in particular epoxy resin and its hardener (thermoactive polymer additives), are defined as the main component of epoxy-bitumen composite (hereinafter - EBC), which is part of the asphalt concrete mixture. The article is aimed at highlighting the results of research conducted to determine the physical and mechanical properties of thin-layer asphalt concrete pavement with the use of EBC for its use on highway bridges. According to the results of laboratory tests, epoxy asphalt concrete (hereinafter - EAB) can be considered one of the best choices for the next generation of durable materials for the installation of thin-layer coatings on highway bridges due to their excellent mechanical properties and thermal stability, as well as economic viability, taking into account the absence of the need for waterproofing of the bridge deck, excessive maintenance and repair costs and a long service life. Problem statement. One of the main mechanisms of destruction of asphalt concrete coatings on highway bridges, especially with orthotropic slabs, is its constant dynamics from external influences, which causes significant deformations that mercilessly affect the durability of the entire bridge structure. Taking into account the thermoreactive nature of epoxy components, the idea of using them as a bitumen modifier arose in order to minimize deformations of the asphalt concrete coating on bridges, reduce the load from the weight of the bridge deck on span structures, and also increase the resistance of the coating to the influence of aggressive environments. In order to obtain high-quality research results for the further possibility of ensuring the installation of coatings on bridges with the best operational characteristics and the most efficient use of labor and resources, studies of the physical and mechanical characteristics of EAB were carried out according to the Superpave methodology.
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Dicu, Mihai, Andreea Matei, and Constantin Dorinel Voiniţchi. "Study of the Influence of Fibres Type and Dosage on Properties of Concrete for Airport Pavements." Romanian Journal of Transport Infrastructure 8, no. 1 (July 1, 2019): 102–13. http://dx.doi.org/10.2478/rjti-2019-0006.
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Abstract The paper follows the potential practice of fiber reinforced concrete (FRC) as a solution for airport`s runway pavements, in order to increase the bearing strength, resulting in decreasing the height of the concrete layer that is currently used. Experimentally, the study focuses on the properties of fiber reinforced Portland cement concrete using 3 different percentages (0.5%, 1% and 1.5% of the concrete volume) and 4 different types of fiber (for 1% percentage – hooked steel fiber 50 mm length, hooked steel fiber 30 mm length, crimped steel fiber 30 mm length and polypropylene fiber 50 mm lenght), using as reference a plain concrete with 5 MPa flexural strength. More exactly, the study presents the change in compressive and flexural strength, shrinkage, thermal expansion factor, elastic modulus and Poisson`s ratio over fiber type and dosage. For the highest performance concrete (7 MPa flexural strength), it has been made a study using two methods for rigid airport pavements design (general method and optimized method), and one method for evaluation of bearing strength (ACN – PCN method), which is compared to a plain 5 MPa concrete. Furthermore, the decrease in the slab`s thickness proportionally to the growth of the flexural strength is emphasized by evaluating the slab`s height for a high performance 9 MPa concrete using both design methods.
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Kim, Kukjoo, Sangyoung Han, Mang Tia, and James Greene. "Optimization of parameters affecting horizontal cracking in continuously reinforced concrete pavement (CRCP)." Canadian Journal of Civil Engineering 46, no. 7 (July 2019): 634–42. http://dx.doi.org/10.1139/cjce-2017-0679.
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Field evaluation of distresses in continuously reinforced concrete pavement (CRCP) indicated punch-out distress associated with horizontal cracking at the depth of the longitudinal steel is the most severe performance problem in CRCP. The developed 3-D model was used to perform a parametric analysis to determine the effects of critical loading location, concrete properties, and longitudinal steel design on horizontal cracking potential. The maximum vertical tensile stresses in the concrete were slightly affected by the coefficient of thermal expansion of the concrete. The critical tensile stresses in the concrete were observed to decrease as the base modulus, slab–base friction, slab thickness, and transverse crack spacing increase. The vertical tensile stresses significantly decreased when the longitudinal steel spacing decreased. The use of varying longitudinal steel spacing and reducing the depth of steel may be one of the ways to reduce the horizontal cracking potential without changing the steel ratio of the slab.
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Wong, M. Bill. "Inelastic Behaviour of Concrete/Steel Composite Beam in Fire." Key Engineering Materials 340-341 (June 2007): 131–36. http://dx.doi.org/10.4028/www.scientific.net/kem.340-341.131.
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The configuration of a steel beam in a concrete/steel composite floor in fire gives rise to a non-uniform temperature profile across the depth of the cross-section. This temperature profile affects the deflection of the steel beam in two ways: thermal bowing due to non-uniform thermal strains and beam deflection due to imposed loads. The beam deflection becomes larger as the elastic properties of the steel beam deteriorate when the temperature is rising. The deflection increases rapidly when the cross-section of the steel beam starts to yield. This paper presents a method for the calculation of the total deflection of a steel beam in a steel/concrete composite floor in fire when the beam is loaded beyond its elastic limit. In this study, the steel beam is assumed to support the concrete floor slab simply at its ends without composite actions.
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Dhanraj, A. A., and C. Selvamony. "A Comparative Study on Thermal Insulation Properties of Partial Replacement of Fine Aggregate by E-Waste Material (FR-4) in M30Grade with Conventional Concrete." Key Engineering Materials 692 (May 2016): 104–9. http://dx.doi.org/10.4028/www.scientific.net/kem.692.104.
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The purpose of this experiment is to analyze the steady state condition in a concrete slab. Temperature measurements were made for each scenario and were used along with physical dimensions to compute various heat transfer parameters. In this paper, the investigation was made by the partial replacement in the coarse aggregate with E-waste (PCB cutting waste) (FR-4) in the conventional concrete. The durability test such as compressive strength test, split tensile and flexure strength were made and the results analyzed. The investigation is made by casting slab panels of various thickness (1’ x 1’ x 0’-2”, 1’ x 1’ x 0’-4”, 1’ x 1’ x 0’-6”, 1’ x 1’ x 0’-8” & 1’ x 1’ x 0’-10”) with same area and different temperature. These panels were allowed for curing of 28 days and tested in a closed chamber. The heat was transferred from one part of chamber to another chamber through the slab element. Then the heat transformation and U-factor will be calculated and the insulation properties of the e-waste concrete with conventional concrete
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D. Huseyn Mammadov, Ph, and Musa Gadirov. "Application of Slags from Thermal Power Station as an Effective Initial Material in the Production of Artificial Porous Filler." International Journal of Engineering & Technology 7, no. 3.14 (July 25, 2018): 461. http://dx.doi.org/10.14419/ijet.v7i3.14.17043.
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The article is devoted to obtaining an artificial porous filler from industrial wastes, in particular from granulated slags, or ash-slag mixtures from Thermal Power Station. The developed technology provides the opportunity to expand the raw material base of artificial porous filler production for lightweight concrete, and it allows us to solve the problem of involving secondary resources in the production of construction materials and protection of the environment from pollution.According to the results of research, the intervals of the bloating temperature have been determined, the technology of obtaining an artificial porous filler from slag and ash-slag mixtures from Thermal Power Station has been developed, and the mainphysical-mechanical properties of the filler obtained have been studied. It was established that the obtained artificial porous filler meets the requirements of the current standard in its physical-mechanical properties. It was found that on the basis of them, heat-insulating, heat-insulating-constructional and structural lightweight concrete for enclosing and bearing constructions have been obtained.
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Zokaei, Monireh, Mansour Fakhri, and Saeed Rahiminezhad. "A Parametric Study of Jointed Plain Concrete Pavement Using Finite Element Modeling." Modern Applied Science 11, no. 11 (October 31, 2017): 75. http://dx.doi.org/10.5539/mas.v11n11p75.
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Concrete pavements face various types of distresses such as longitudinal, transverse, and joint cracking due to traffic loading and thermal stresses. The objective of this investigation was to develop Three-Dimensional Finite-Element Models (3D-FEM) to assess the performance of dowel in Jointed Plain Concrete Pavement (JPCP).Finite-element modeling is a powerful tool that can be used for the simulation of the structural response of pavements under the effects of different loading condition. Most of the previous studies ignored important factors, including the combined effect of dynamic axle loads and thermal gradient. Overcoming the shortcomings of the previous studies, this study investigated the pavement response under the effect of some model parameters. The result of the study was verified by a comparison with field measurements. Results also showed that the combined negative gradient and axle loads located at the transverse joint subject the top of mid-slab, to high tensile stress that may explain the initiation of top-down cracks. These stresses increase under corner loading when the slab length is increased. In general, the study presented that the developed 3D-FEM is suitable for identifying the effect of different design features including pavement geometry, material properties, thermal gradients, and axle load and configuration on the structural response of rigid pavements.
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Kubenková, Kateřina, Marek Jašek, and Vladan Panovec. "Research of the Temperature Field Process in the Soil for a Home - Founded on a Foam Glass Granulate." Advanced Materials Research 1041 (October 2014): 257–60. http://dx.doi.org/10.4028/www.scientific.net/amr.1041.257.
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Foam glass granulate is environmentally friendly, heat-insulating building material which is made from recycled glass waste. It is a very porous material with low density, with good thermal insulation properties, high static load capacity and almost zero water absorption. The paper deals with the research of the temperature field process in the soil under the floor of a passive house built on a reinforced concrete slab foundation with a layer of compacted subsoil using raw materials friendly to the environment in the form of granules of foamed glass. This method of progressive foundation of the building addresses the elimination of thermal bridges at the base and establish a continuous thermal insulating of the building envelope without thermal bridges.
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Zubeck, Hannele K., and Ted S. Vinson. "Prediction of Low-Temperature Cracking of Asphalt Concrete Mixtures with Thermal Stress Restrained Specimen Test Results." Transportation Research Record: Journal of the Transportation Research Board 1545, no. 1 (January 1996): 50–58. http://dx.doi.org/10.1177/0361198196154500107.
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A deterministic model and a probabilistic model were developed to predict low-temperature crack spacing as a function of time using thermal stress restrained specimen test results, pavement thickness and bulk density, pavement restraint conditions, and air temperature. The effect of aging on pavement properties was incorporated in the models by predicting the field aging with long-term oven aging treatment in the laboratory. The calculation of the crack spacing is based on the theory that the pavement slab cracks when the pavement temperature reaches the cracking temperature of the mixture and the slab is fully restrained. The deterministic model predicts crack spacing with time, whereas the probabilistic model predicts crack spacing and its variation with time and yields the reliability of the design with regard to a minimum acceptable crack spacing criterion defined by road authorities. The probabilistic model is recommended for use in predicting the low-temperature cracking of asphalt concrete mixtures.
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Elchishcheva, Tatiana F. "Safe usage of external enclosures under adverse environmental exposure." Vestnik MGSU, no. 5 (May 2019): 570–88. http://dx.doi.org/10.22227/1997-0935.2019.5.570-588.
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Introduction. The study considers the issue of safety of the human vital activity environment in the field of construction and usage of buildings, which includes, along with other types of safety, thermal, biological and mechanical safety. The last ones cannot be provided if there are inorganic hygroscopic salts in construction materials of external enclosures due to influence of the salts on the thermal, mechanical and other properties of the materials. Thermal conductivity coefficient of damped saline construction materials is determined on a developed experimental facility operating according to the principle of unsteady thermal conditions. A statistical analysis of the experimental results on thermal conductivity of materials possessing various structures and densities is carried out. Significance of the influence of the “salt content” factor on the thermal conductivity of saline materials in comparison with control non-saline samples is revealed.
Materials and methods. Construction materials for the study are selected as follows: autoclave lime-and-sand brick and burnt brick with a density of 1800 kg/m3, autoclave foamed silicate with a density of 650 kg/m3, wood concrete with a density of 616 kg/m3 and mineral wool slabs with a density of 150 kg/m3. The generally accepted methods of laboratory research and statistical processing of experimental results are used. Laboratory methods include preparation, salinization with sodium chloride, potassium sulfate and calcium chloride, and measurements of the thermal conductivity coefficient of construction material samples.
Results. The determination of thermal conductivity of wetted saline materials under unsteady thermal conditions makes it possible to eliminate drying of the samples and migration of salts and moisture. The presence of salt crystals increases the thermal conductivity of dry materials up to 80 % (rel.). Damping the samples promotes the dissolution of the crystals and lowering the thermal conductivity of the samples to values lower than those of non-saline samples with the same moisture content.
Conclusions. The study proves the significance of the salinization effect on the thermal and physical characteristics of construction materials that must be taken into account when thermal engineering calculating external enclosures and predicting their moisture state during usage.
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Kovalov, Andrii, Roman Purdenko, Yurii Otrosh, Vitalii Tоmеnkо, Nina Rashkevich, Eduard Shcholokov, Mykola Pidhornyy, Nina Zolotova, and Oleg Suprun. "Assessment of fire resistance of fireproof reinforced concrete structures." Eastern-European Journal of Enterprise Technologies 5, no. 1 (119) (October 30, 2022): 53–61. http://dx.doi.org/10.15587/1729-4061.2022.266219.
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A finite-element model for the heat engineering calculation of fireproof reinforced concrete slab has been built, which is designed to assess the fire resistance of unprotected reinforced concrete structures. A feature of the model is the correct choice of types of heat transfer in the cavities of reinforced concrete ceilings. An algorithm that includes experimental and calculation procedures in determining the fire resistance of unprotected reinforced concrete structures has been applied. The initial, boundary conditions for the construction of the model were formulated; the thermophysical properties of materials were substantiated. Thermal calculation of fireproof multi-hollow reinforced concrete ceiling under conditions of fire was carried out. The adequacy of the developed finite-element model was checked. A satisfactory convergence of experimental and calculated temperatures with an accuracy of 10 % was established, which would suffice for the engineering calculations. The model built makes it possible to assess the fire resistance of unprotected reinforced concrete structures. Thus, there is reason to argue that the model constructed can partially or completely replace the experimental assessment of fire resistance, provided that the construction and setting of the model parameters are correct
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Selden, Kristi L., and Amit H. Varma. "Composite beams under fire loading: numerical modeling of behavior." Journal of Structural Fire Engineering 7, no. 2 (June 13, 2016): 142–57. http://dx.doi.org/10.1108/jsfe-06-2016-011.
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Purpose The purpose of this study was to develop a three-dimensional (3D) finite element modeling (FEM) technique using the commercially available program ABAQUS to predict the thermal and structural behavior of composite beams under fire loading. Design/methodology/approach The model was benchmarked using experimental test data, and it accounts for temperature-dependent material properties, force-slip-temperature relationship for the shear studs and concrete cracking. Findings It was determined that composite beams can be modeled with this sequentially coupled thermal-structural 3D FEM to predict the displacement versus bottom flange temperature response and associated composite beam failure modes, including compression failure in the concrete slab, runaway deflection because of yielding of the steel beam or fracture of the shear studs. Originality/value The Eurocode stress-strain-temperature (σ-ε-T) material model for structural steel and concrete conservatively predict the composite beam deflections at temperatures above 500°C. Models that use the National Institute of Standards and Technology (NIST) stress-strain-temperature (σ-ε-T) material model more closely match the measured deflection response, as compared to the results using the Eurocode model. However, in some cases, the NIST model underestimates the composite beam deflections at temperatures above 500°C.
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Qiu, Ji Sheng. "Study on Nonlinear Finite Element Analysis Method of Multi-Ribbed Composite Slab Structure Containing Steel Fibers." Advanced Materials Research 250-253 (May 2011): 3975–82. http://dx.doi.org/10.4028/www.scientific.net/amr.250-253.3975.
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Steel fiber concrete multi-ribbed composite slab system includes material composite and structure type composite, which has good mechanical and thermal insulation properties. This paper presents an assessment of the structure investigated using three-dimensional nonlinear finite elemental analysis. The analysis firstly has focused on solving the constitutive relation of the materials and the effect of steel fiber to determine the finite element simulation. Moreover nonlinear finite element analysis for the mechanical properties of the whole process on the composite structure system has been presented in this paper, and by changing the fiber volume fractionvf(0%, 1%, 2% and 3%) the parameter has been discussed. The analysis results show that stress distributions of the structure are close for different concrete strength and steel fiber volume fraction before formation of the plastic hinge lines of the upper edges. When the structure began to crack and the plastic hinge lines of upper edge gradually formed, due to the influence of the redistribution of internal forces, the steel fiber volume fraction has significant impact for the mechanic behavior of the structure. In addition, the steel fiber volume fraction on the developing and distribution of the cracks has little effect. This analysis method and results for the steel fiber concrete multi-ribbed composite structure can provide some valuable references for the structure research and application.