Дисертації з теми "Steele fibre"
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1
Hu, Hang. "Mechanical properties of blended steel fibre reinforced concrete using manufactured and recycled fibres from tyres." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/21168/.
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Jeffers, Ann E. "A Fiber-Based Approach for Modeling Beam-Columns under Fire Loading." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/38692.
Повний текст джерелаАнотація:
The work described herein emphasizes a new fiber-based approach to modeling the response of structural frames subjected to realistic fire conditions. The proposed approach involves the development and validation of two finite elements that can be used collectively to simulate the thermal and mechanical response of structural frames at elevated temperatures. To model the thermal response, a special-purpose fiber heat transfer element is introduced. The first of its kind, the fiber heat transfer element uses a combination of finite element and finite difference methods to provide an accurate and highly efficient solution to the three-dimensional thermal problem. To simulate the mechanical response, a flexibility-based fiber beam-column element is used. The element presented here extends the formulation of Taucer et al. (1991) to include thermal effects, geometric nonlinearities, and residual stresses.
Both fiber elements are implemented in ABAQUS (2007) using the user-defined element (UEL) subroutine. The element formulations are verified by analyses of benchmark experimental tests and comparisons with traditional finite elements. Results indicate that both elements offer superior accuracy and computational efficiency when compared to traditional methods of analysis. Analyses of structures subjected to non-uniform heating emphasize the advantages of the fiber-based approach.
To demonstrate a realistic application of the proposed approach, the work concludes with an investigation of the response of unprotected steel beams subjected to localized fires. Because realistic fires are considered, the treatment of strain reversal upon cooling is also addressed. The analyses are used to demonstrate that the standard fire test is generally unconservative at predicting the time at failure of a structure subjected to realistic fire conditions, since failure depends more on the evolution of temperatures within the steel beams than the duration of fire exposure. The analyses also show that critical temperatures from the standard fire test are conservative and thus offer a better means for predicting failure in steel structures within the scope of the standard fire test.Ph. D.
3
Mbewe, Peter Binali Kamowa. "Development of analytical flexural models for steel fibre-reinforced concrete beams with and without steel bars." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/18088.
Повний текст джерелаАнотація:
Thesis (MScEng)--Stellenbosch University, 2011.ENGLISH ABSTRACT: There is an increasing demand for the development and use of innovative materials with reduced cost of construction while offering improved structural properties. Steel fibre reinforced concrete (SFRC) can be used as a structural material to substitute the conventional reinforcing bars partially or fully. However, there is little or no codified approach on the design procedures for SFRC members in the latest guidelines outlined in the draft 2010 Model code. It is against this background that analytical methods are derived in this study for the determination of the flexural capacity of strain-softening, deflection-hardening SFRC with and without steel reinforcing bars. Models used for the determination of the flexural capacity of SFRC rectangular sections are based on equivalent stress blocks for both compression and tensile stresses. These are derived from an elastic-perfect plastic model for compression and either an elastic-constant post-peak response or Rilem’s multi-linear model for tension, in which strain compatibility and force equilibrium theories are used. By employing the equivalent stress blocks for both tensile and compressive stress states, parameters are defined by converting the actual stress-strain distribution to an equivalent stress block, depending on the ratio of yield (or cracking) strain and post-yield (post-cracking) strains. Due to the simplicity of a drop-down tensile model and a bilinear compression model, these material models are used for the subsequent derivation of the flexural models for both SFRC with and without steel reinforcing bars. An experimental program is designed and executed for model verification. This includes material characterisation experiments for the determination of material model input parameters, and main beam flexural experiments for the determination of the beam bending capacity. An indirect tensile test is used for the characterisation of the tensile behaviour while a four-point bending test is used for beam bending behaviour. Both flexural models for SFRC with and without reinforcing bars have been verified to fairly predict the flexural capacity of the beams. However, the flexural model for SFRC with steel bars offers some challenges as to whether the synergetic effect of using both steel bars and steel fibres should be incorporated at the low fibre volumes as used in the verification exercise. Furthermore, the use of indirect methods to characterise tensile behaviour added some uncertainties in the material model parameters and hence may have affected the predictability of the model. More research on the verification of the models is required to enable the use of a wider concrete strength spectrum for the verification and possible modification of the models. Studies on the model uncertainty may also help determine the reliable safety factor for the use of the model in predicting design strength of beam sections at a prescribed reliability index.
AFRIKAANSE OPSOMMING: Daar is ‘n groeiende aanvraag na die ontwikkeling en gebruik van innoverende materiale met verminderde konstruksiekoste maar verbeterde strukturele eienskappe. Staalvesel-gewapende beton (SVGB) kan gebruik word as strukturele materiaal om die konvensionele wapeningstawe gedeeltelik of ten volle te vervang. Daar is egter min of geen gekodifiseerde benaderings tot die ontwerpprosedures vir SVGB-dele in die nuutste riglyne uitgestippel in die konsepweergawe van die 2010 Modelkode nie. Dit is teen hierdie agtergrond dat in hierdie studie analitiese metodes afgelei is vir die bepaling van die buigkapasiteit van spanning-versagtende, defleksie-verhardende SVGB met en sonder staalbewapeningstawe. Modelle wat gebruik is vir die bepaling van die buigkapasiteit van SVGB reghoekige snitte is gebaseer op ekwivalente spanningsblokke vir beide druk- en trekspannings. Hierdie is afgelei van ‘n elasties-perfekte plastiese model vir druk en óf ‘n elasties-konstante post-piek respons óf Rilem se multi-lineêre model vir spanning, waarin teorieë vir drukkapasiteit en krag-ewewig gebruik is. Deur die ekwivalente spanningsblokke vir beide trek- en drukspanningstoestande te implementeer, is parameters bepaal deur die werklike verspreiding van spanningsdruk om te wissel na ‘n ekwivalente spanningsblok, afhangend van die verhouding van swig- (of kraak-)spanning en post-swig (post-kraak) spannings. Te wyte aan die eenvoud van ‘n aftrek trekmodel en ‘n bilineêre kompressiemodel, is hierdie materiaalmodelle gebruik vir die daaropvolgende afleiding van die buigingsmodelle vir beide SVGB met en sonder staalbewapeningstawe. ‘n Eksperimentele program vir modelkontrolering is ontwerp en uitgevoer. Dit sluit eksperimente in vir materiaalbeskrywing, om invoerparameters van materiaalmodelle te bepaal, asook eksperimente vir hoofbalkbuigings, om balkbuigingskapasiteit te bepaal. ‘n Indirekte trektoets is gebruik vir die beskrywing van die trekgedrag, terwyl ‘n vierpuntbuigingstoets gebruik is vir balkbuiggedrag. Dit is bewys dat beide buigingsmodelle vir SVGB met en sonder staalbewapeningstawe die buigingskapasiteit van die balke redelik akkuraat kan voorspel. Nietemin, bied die buigingsmodel vir SVGB met staalbewapeningstawe sekere uitdagings: die vraag ontstaan rondom die insluiting van die sinergetiese effek van die gebruik van beide staalstawe en staalvesels met die lae veselvolumes soos gebruik in die kontroleringsoefening. Verder het die gebruik van indirekte metodes om die buigingsgedrag te bepaal, onsekerhede gevoeg by die materiaalmodelparameters en dit mag dus as sulks die voorspelbaarheid van die model beïnvloed. Meer navorsing moet uitgevoer word oor die kontrolering van die modelle sodat ‘n wyer spektrum van betonsterkte gebruik kan word vir die verifikasie en moontlike aanpassing van die modelle. Navorsing oor die wisselvalligheid van die modelle mag ook help om die betroubare veiligheidsfaktor te bepaal vir die model se gebruik in die berekening van ontwerpkrag van balkdele teen ‘n voorgeskrewe betroubaarheidsindeks.
4
Baczkowski, Bartlomiej Jan. "Steel fibre reinforced concrete coupling beams /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202007%20BACZKO.
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Mpanga-A-Kangaj, Christian. "Pull-out of hooked end steel fibres : experimental and numerical study." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/40820.
Повний текст джерелаАнотація:
Abstract
The reinforcement of concrete with steel fibres changes the failure of the composite material from catastrophic brittle failure to pseudo-ductile behaviour as a result of crack-bridging by the fibres, and the additional work which is absorbed by fibre pull-out. A good understanding of the properties of the fibre-reinforced concrete depends on an understanding of the fibre pull-out process. The main aim of the current study is to investigate, both experimentally and numerically, the pull-out behaviour of a single hooked end steel fibre from epoxy matrix, where epoxy was chosen to replace concrete in order to enable visualisation of the pull-out process. The experimental and numerical results both contribute to the development of a physical understanding of the mechanism of pull-out.
Experimental studies included the evaluation of the mechanical properties of hooked end steel fibre and epoxy matrix by means of tensile tests, the manufacturing of pull-out specimens consisting of a single hooked end steel fibre embedded in epoxy matrix, and the experimental characterisation of the fibre pull-out. The significant features (peaks and minima) of the load vs. displacement graph were correlated to stills taken from a video of the pull-out process, in which the plastic deformation of the fibre is evident. Small deformations (spalling) were also observed in the matrix. A model is proposed for the mechanisms which interact during the pull-out process.Dissertation (MEng)--University of Pretoria, 2013.
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Mechanical and Aeronautical Engineering
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6
Darwish, I. Y. S. "Steel fibre-reinforced concrete elements in shear." Thesis, Bucks New University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375129.
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Tao, Xiaoya. "Pull-out behaviour of steel reinforced cement composites." Thesis, University of Glasgow, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343924.
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Ige, Olubisi A. "Key factors affecting distribution and orientation of fibres in steel fibre reinforced concrete and subsequent effects on mechanical properties." Thesis, University of Portsmouth, 2017. https://researchportal.port.ac.uk/portal/en/theses/key-factors-affecting-distribution-and-orientation-of-fibres-in-steel-fibre-reinforced-concrete-and-subsequent-effects-on-mechanical-properties(186800d2-458c-4c66-9400-5d3e0d1acf58).html.
Повний текст джерелаАнотація:
Use of fibres to reinforce brittle materials for better performance in buildings and for construction purposes has been employed since time immemorial. Inclusion of steel fibres in concrete therefore, has always improved the post-cracking strength and concrete ductility to a large extent. Nevertheless, there is no doubt that it has become imperative to have more understanding of the internal workings of steel fibre reinforced concrete to fully exploit its potential in practice. In this PhD study, investigation of distribution and orientation of steel fibres within steel fibre reinforced concrete, studying how the positioning of steel fibres in SFRC (steel fibre reinforced concrete) matrix affects the post-cracking strength and other properties that enhance concrete ductility is reported. Variables selected for this study were those considered to influence how steel fibres and concrete matrix associate together during mixing. Hooked-end steel fibres with 50 mm and 60 mm length, of varying diameter resulting in different aspect ratio (ratio of length to diameter of fibre) of 45, 65 and 80, and dosages of 0 kg/m³, 25 kg/m³, 40 kg/m³, 50 kg/m³ and 60 kg/m³ were employed with maximum sizes of coarse aggregate of 10 mm and 20 mm. The same mix proportions of concrete were used throughout the investigation. Workability of the fresh mix was carried out through slump test, flexural performance was assessed through beam and slab tests at 28 day while compressive strength was also measured using cubes. Subsequently, cores were extracted from these panels and X-ray computed tomography was employed for imaging the cores while Insight Toolkit Software was used to analyse the position of fibres in hardened concrete. The experimental results show that the strength performance of steel fibre reinforced concrete improved drastically when compared to plain concrete without fibres. Remarkable improvements were observed at larger dosages of steel fibres, and with fibres with highest aspect ratio of 80 noted to give the best results which suggests that aspect ratio of fibre is critical to SFRC performance. It was found that fibre effects on compressive strength is slightly pronounced, with optimum compressive strength of 68 MPa noticed at fibre dosage of 50 kg/m³ and with fibre of 80 l/d ratio with 20 mm aggregate mixture which is about increase of 8 MPa when compared with plain concrete. Also, in SFRC beams, there were up to 83% increase in maximum stress reached when compared to unreinforced concrete. Moreover, it was found that the results of X-ray CT image analysis by The Insight Toolkit software correlate well with the outcome of mechanical performance of steel fibre reinforced concrete. The slab test results show that mixtures containing 10 mm maximum aggregate size sustain higher load than those of 20 mm counterparts. Harmonization of beam and slab results using yield line analysis revealed that the values of theoretical and experimental failure loads are reasonably close for slabs containing 20 mm maximum aggregate size while the analysis does not agree perfectly with slabs containing 10 mm maximum aggregate size. The 3D rendering images of SFRC cores show that steel fibres are generally positioned horizontally in the slabs which can be seen to be more pronounced in 10 mm maximum aggregate mixes resulting in their ability to sustain higher failure loads. The study has revealed a clear relationship between the geometry of steel fibre and maximum aggregate size, establishing the fibre-aggregate interaction effects on post-cracking capacity of SFRC. Finally, the study has quantitatively measured the distribution and orientation of steel fibre within the concrete matrix while the correlation between the internal mechanism and the mechanical properties of SFRC has been established.
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Carlesso, Débora Martinello. "Flexural fatigue of pre-cracked fibre reinforced concrete: experimental study and numerical modelling." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/669488.
Повний текст джерелаАнотація:
Fibre reinforced concrete (FRC) is recognized as suitable material for structural applications. The number of national codes that have approved it is an evidence. Structures where FRC is generally used can be subjected to fatigue loads and are expected to resist millions of cycles during their service life. Cyclic loads affect significantly the characteristics of materials and can cause fatigue failures. The most demanded cross-sections being cracked under tensile stresses due to direct loads or imposed deformations. Commonly, publications report fatigue behaviour of concrete under compression and are valid for uncracked sections. Imprecision in fatigue prescriptions are reflected through formulation of models that contemplate a probabilistic approach, or an introduction of high safety coefficients within construction codes. The aim of the present doctoral thesis is to perform a structural design oriented analysis on the behaviour of pre-cracked FRC subjected to flexural fatigue loads. FRC with steel and polypropylene fibre with different volume content were investigated by means of three-point bending tests, considering an initial crack width accepted in the service limit state. The mechanical behaviour of FRC were analysed in terms of applied load level, crack opening displacement (CMOD) and fatigue life. The residual flexural tensile strength was assessed after these tests to estimate the impact of the cycles in the remaining resistant capacity of the specimens. Results suggest that the mechanism of crack propagation is independent of the fibre type and content and the monotonic load-crack opening displacement curve might be used as deformation failure criterion for FRC under flexural fatigue loading. The conducted probabilistic approach allows predicting the fatigue strength of concrete reinforced with steel fibres. The findings postulate the proposal of a model to predict the evolution of the crack-opening and the remaining resistant capacity. An optimisation procedure is proposed to derive the model parameters using a limited number of initial load cycles. This doctoral thesis provides knowledge and data that may aid further research and contribute to the future development of design recommendations.El hormigón reforzado con fibra (FRC) se reconoce como material adecuado para aplicaciones estructurales. El número de normativas que lo han aprobado es una evidencia. Las estructuras donde generalmente se usa FRC pueden estar sujetas a cargas de fatiga y se espera que resistan millones de ciclos durante su vida útil. Las cargas cíclicas afectan significativamente a las características de los materiales y pueden causar roturas por fatiga. Las secciones transversales más demandadas se fisuran bajo tensión debido a cargas directas o deformaciones impuestas. Comúnmente, las publicaciones informan del comportamiento de fatiga del hormigón bajo compresión y son válidas para secciones no fisuradas. La imprecisión de las recomendaciones se refleja a través de la formulación de modelos que contemplan un enfoque probabilístico o la introducción de altos coeficientes de seguridad dentro de los códigos de construcción. El objetivo de la presente tesis doctoral es realizar un análisis orientado al diseño estructural sobre el comportamiento del FRC pre-fisurado sometido a cargas de fatiga por flexión. Se investigaron FRC con fibras de acero y polipropileno con diferentes contenidos de fibras mediante pruebas de flexotracción a tres puntos, considerando un ancho de fisura inicial aceptado en el estado límite de servicio. El comportamiento mecánico del FRC se analizó en términos de nivel de carga aplicada, desplazamiento de apertura de fisura (CMOD) y vida útil bajo fatiga. La resistencia residual a flexotracción se evaluó después de los ciclos de fatiga para estimar el impacto de los ciclos en la capacidad de resistencia restante de las muestras. Los resultados sugieren que el mecanismo de propagación de fisuras es independiente del tipo y contenido de fibra y la curva monotónica de CMOD podría ser utilizada como criterio de falla de deformación para FRC bajo carga de fatiga por flexotracción. El enfoque probabilístico realizado permite predecir la resistencia a la fatiga del hormigón reforzado con fibras de acero. Los resultados postulan la propuesta de un modelo para predecir la evolución de la apertura de fisura y la capacidad resistente remanente. Se propone un procedimiento de optimización para derivar los parámetros del modelo utilizando un número limitado de ciclos de carga inicial. Esta tesis doctoral proporciona conocimiento y datos que pueden ayudar a futuras investigaciones y contribuir al desarrollo futuro de recomendaciones de diseño.
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Burrell, Russell P. "Performance of Steel Fibre Reinforced Concrete Columns under Shock Tube Induced Shock Wave Loading." Thesis, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23516.
Повний текст джерелаАнотація:
It is important to ensure that vulnerable structures (federal and provincial offices, military structures, embassies, etc) are blast resistant to safeguard life and critical infrastructure. In the wake of recent malicious attacks and accidental explosions, it is becoming increasingly important to ensure that columns in structures are properly detailed to provide the ductility and continuity necessary to prevent progressive collapse. Research has shown that steel fibre reinforced concrete (SFRC) can enhance many of the properties of concrete, including improved post-cracking tensile capacity, enhanced shear resistance, and increased ductility. The enhanced properties of SFRC make it an ideal candidate for use in the blast resistant design of structures. There is limited research on the behaviour of SFRC under high strain rates, including impact and blast loading, and some of this data is conflicting, with some researchers showing that the additional ductility normally evident in SFRC is absent or reduced at high strain loading. On the other hand, other data indicates that SFRC can improve toughness and energy-absorption capacity under extreme loading conditions. This thesis presents the results of experimental research involving tests of scaled reinforced concrete columns exposed to shock wave induced impulsive loads using the University of Ottawa Shock Tube.
A total of 13 half-scale steel fibre reinforced concrete columns, 8 with normal strength steel fibre reinforced concrete (SFRC) and 5 with an ultra high performance fibre reinforced concrete (UHPFRC), were constructed and tested under simulated blast pressures. The columns were designed according to CSA A23.3 standards for both seismic and non-seismic regions, using various fibre amounts and types. Each column was exposed to similar shock wave loads in order to provide direct comparisons between seismic and non-seismically detailed columns, amount of steel fibres, type of steel fibres, and type of concrete.
The dynamic response of the columns tested in the experimental program is predicted by generating dynamic load-deformation resistance functions for SFRC and UHPFRC columns and using single degree of freedom dynamic analysis software, RCBlast. The analytical results are compared to experimental data, and shown to accurately predict the maximum mid-span displacements of the fibre reinforced concrete columns under shock wave loading.
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Rengarajan, Muralidharan. "Laboratory testing of shotcrete with fibres of steel, basalt or synthetic materials." Thesis, KTH, Betongbyggnad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-287310.
Повний текст джерелаАнотація:
Shotcrete or sprayed concrete has become an inevitable material for stabilising and supporting hard rock tunnels. To prevent rock block fallouts in the excavated tunnel, shotcrete is pneumatically projected under high pressure on the rock surface. This method has proven to reduce the construction time drastically, and the addition of fibres in the shotcrete material results in Fibre Reinforced Shotcrete (FRS). The fibres increased the strength of the parent matrix and made the reinforcement bar (mesh) placing procedure with its heavy labour work unnecessary. Even though FRS have been in use for many years, to design FRS lining there are currently no complete, widely used guidelines. Traditionally, the most frequently used testing was a traditional beam testing method which helps to determine the FRS mechanical properties. Previous studies prove that the result from beams often show a high scatter in the results. Another proposed standard testing method is the Round Determinate Panel method to determine the energy absorption capacity. This method has the potential to be a reliable test procedure with a repeatable and predictable crack pattern.In this project, an experimental investigation was carried out to understand the behaviour of macro fibres of steel, basalt and synthetic materials in FRS. The specimens were sprayed in situ and cast in laboratory, of which the in situ samples were assigned to different curing conditions. The test standard ASTM C-1550 was used to design the round panels and SS-EN 14488-3 for the beams. Each type of FRS specimen’s compressive strength was tested, evaluated and compared. The single fibre pullout strength was tested to determine the bond strength between shotcrete and fibres.The calculated results showed the coefficient of variation (COV) of energy absorption capacity from panels varied within 3 % – 13 % and the residual strength of beams within 12 % – 35 %. Irrespective of testing method, the Dramix 3D steel fibre and Minibars basalt fibre for the tested cases showed the lowest dispersion of result. Minibars showed a significant increase in compressive strength compared to the other fibres. Single fibre pullout testing concluded that the steel fibre had superior load capacity at the first crack. Minibars showed a strength close to that of steel fibres and a failure mode similar to that with synthetic fibres.
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Ali, Ahsan. "Bond behavior of lightweight steel fibre-reinforced concrete." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2017. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-230104.
Повний текст джерелаАнотація:
This research was undertaken for studying the bond behaviour of Lightweight Fibre-reinforced Concrete (LWFC). Lightweight concrete is inherently weak in tension and has higher brittleness than the conventional concrete. To improve these and other properties, it is generally reinforced with deformed bars and fibres. There are number of studies that favour the use of Steel fibres, however such studies are mainly focused either on normal weight concrete or on the mechanical properties of different concretes. There are also different committee reports and in some cases specific sections of codes that specifically deal with the normal weight fibre-reinforced concrete.
However, such is not the case with lightweight fibre-reinforced concrete; there is limited literature available especially on the Bond of lightweight fibre-reinforced concrete.
In current research work effect of fibres is studied on the bond behaviour of the lightweight reinforced concrete. Since most of code provisions for bond are based on experimental work originally carried out on conventional concrete, effect of fibres on bond of conventional concrete was therefore also included in present research domain.
Main bond tests were carried out using Pull-out test methodology. Test results indicate that the ultimate bond strength of conventional concrete when reinforced with steel fibres increased by 29%. However due to very low density and high porosity of lightweight aggregates, no significant improvement on bond strength of LWFC, as a result of fibres’ addition could be observed. Nevertheless, there is noteworthy improvement in the post-cracking bond strength of LWFC. Besides this, current bond-stress slip law as defined by Model Code 2010 does not reflect the positive effect of fibres, hence some modifications are suggested.
It is also found that among the existing code expressions for estimation of bond strength, expression proposed by Model Code 2010 presents better results and its effectiveness can be further increased if fibre factor and factor for lightweight concrete are considered.
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Aoude, Hassan. "Structural behaviour of steel fibre reinforced concrete members." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18676.
Повний текст джерелаАнотація:
A series of full-scale axial compression tests was conducted on RC and SFRC columns. The specimens, which were detailed with varying amounts of transverse reinforcement, were cast using a self-consolidating concrete (SCC) mix that contained various quantities of fibres. The results demonstrate that the addition of fibres leads to improvements in load carrying capacity and post-peak response. The results also show that the addition of steel fibres can partially substitute for the transverse reinforcement in RC columns, thereby improving constructability while achieving significant confinement. Analytical models for the prediction of the load-strain response of SFRC columns are presented and validated with the experimental results. The tensile behaviour of SFRC members reinforced with a single reinforcing bar was also studied. The results indicate that the addition of fibres leads to improvements in tension stiffening and crack control. A procedure for predicting the response of tension members, accounting for the presence of fibres, is presented. Experimental investigations were carried out on a series of RC and SFRC beams. The effects of steel fibres on shear capacity, failure mechanism and crack control are studied. The results show that the addition of steel fibres leads to improvements in load carrying capacity and can lead to a more ductile failure. A simple procedure that can be used to predict the ultimate shear capacity of SFRC beams is introduced and validated using results from other researchers.Une série d'essais a été réalisée sur des poteaux de taille réelle soumis à des charges axiales. Les échantillons, qui avaient des quantités variables d'armature transversale, ont été construits en utilisant un béton auto-plaçant qui contenait une quantité variable de fibres métalliques. Les résultants de cette étude expérimentale démontrent que la présence des fibres influence positivement la capacité portante des poteaux. De plus, les résultats montrent que l'utilisation d'un béton renforcé de fibres métalliques (BFM) peut s'avérer une solution appropriée pour assurer une ductilité adéquate aux poteaux. L'auteur propose des modèles analytiques pour prédire le comportement de poteaux chargés uniaxialement. Le comportement sous tension d'éléments en BFM armés d'une seule barre a été étudié. Les résultats montrent que la présence de fibres améliore la résistance en tension. Une procédure pour la prédiction de la réponse des éléments soumis sous tension, prenant en compte la présence de fibres métalliques, est présentée. Des recherches expérimentales furent entreprises afin d'étudier le comportement de poutres sans étriers. L'influence de la présence de fibres sur le développement de fissures ainsi que les mécanismes de ductilité et de rupture est discutée. Les résultats montrent que l'ajout de fibres améliore la capacité portante et la ductilité des poutres. Une procédure est suggérée afin de déterminer la capacité portante de poutres construits avec BFM.
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Al-Mashikhi, Said Omar. "Fibre laser cutting of thin section mild steel." Thesis, University of Nottingham, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.523004.
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Jones, Peter A. "Flexural modelling of steel fibre reinforced sprayed concrete." Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/6885.
Повний текст джерелаАнотація:
A current limitation on the structural use of steel fibre reinforced sprayed concrete (that equally applies to cast steel fibre reinforced concrete) is a distinct lack of accepted design rationales and codes of practice. The research presented here describes the development of a model, based on conventional principles of mechanics, for predicting the flexure behaviour of a wet process sprayed concrete reinforced with deformed steel fibres. The model uses a stress-block diagram to represent the stresses (and resultant forces) that develop at a cracked section by three discrete stress zones: (a) a compressive zone; (b) an uncracked tensile zone; and (3) a cracked tensile zone. By using this concept it is shown that the stress-block diagram, and hence flexural behaviour, is a function of six principal parameters: the compressive stress-strain relation; the tensile stress-strain relation; fibre pull-out behaviour; the number and distribution of fibres across the crack in terms of their positions, orientations and embedment lengths; and the strain/crack-width profile in relation to the deflection of the beam. An experimental investigation was undertaken to obtain relationships for these parameters. Five tests were identified and developed as part of this investigation: a single fibre pull-out test; a compression test; a strain analysis test; a fibre distribution analysis test; and a flexural toughness test. The majority of the investigation used cast (as opposed to sprayed) specimens so that the test variables under investigation could be better controlled. Spraying trials were also successfully undertaken to demonstrate the pumpability and sprayability of the adopted mixes and to verify the use of the model for both cast and sprayed specimens. The results of the modelling analysis showed a reasonable agreement between the model predictions and experimental results in terms of the load-deflection response. However, the accuracy of the model is probably unacceptable for it to be currently used in design. A subsequent analysis highlighted the single fibre pull-out test and the sensitivity of the strain analysis tests as being the mai n cause of the discrepancies. As a result, recommendations are made for how the model might be improved. Overall this research has provided a valuable insight into the reinforcing mechanisms, fracture processes and characteristics of failure associated with the flexural behaviour of steel fibre reinforced concrete. It is envisaged that the proposed model could form the basis of a design rationale which requires only the matrix strength, fibre type, fibre content, beam size and loading geometry as design input parameters. Consequently, it could offer a much needed link between flexural toughness performance and structural design, by allowing designers to make informed choices regarding the mix design in order to meet the ultimate and serviceability requirements of a particular application.
16
Gurusamy, K. "The marine durability of steel fibre reinforced concrete." Thesis, University of Aberdeen, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234802.
Повний текст джерела
17
Jafarifar, Naeimeh. "Shrinkage behaviour of steel-fibre-reinforced-concrete pavements." Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/7475/.
Повний текст джерелаАнотація:
The use of steel fibres extracted from waste tyres as reinforcement for concrete pavements has been developed at the University of Sheffield. The EU funded EcoLanes Project (Economical and sustainable pavement infrastructure for surface transport) undertook extensive research and developed solutions for Steel-Fibre-Reinforced-Concrete (SFRC) pavements with a particular focus on using recycled steel fibres and roller compacted concrete. The current research project ran alongside the EcoLanes project and aimed at contributing towards the development of design guidelines for pavements reinforced with recycled steel fibres. It was achieved through a study on the restrained shrinkage behaviour of Recycled-Steel-Fibre-Reinforced-Roller-Compacted-Concrete (R-SFR-RCC) pavements, and its consequent effect on the load bearing capacity and fatigue performance of pavements. The work in this thesis is mainly based on numerical investigations, but experiments were carried out to obtain the material properties (moisture transport, free shrinkage and mechanical). These basic physical properties were extracted from test results, using inverse analysis. The extent of distress induced by drying shrinkage was evaluated using moisture transport analysis coupled with stress analysis. The effect of shrinkage distress on the load bearing capacity of the pavement was investigated in a comparative way with and without shrinkage. Fatigue test results were also used to study the long-term load-bearing capacity. It was found that the rate of drying and consequent moisture diffusivity in SFRC is higher than for plain concrete and in RCC it is higher than for CC. Moisture diffusivity varies in the range of 0-5 mm2/day for moisture contents lower than 87-92% and then sharply increases to 30 mm2/day for saturated concrete. Free shrinkage is lower for SFRC compared with plain concrete, at early ages. RCC free shrinkage develops at a more uniform rate compared to CC. For the studied SFR-RCC pavement, surface micro-cracks are formed predominantly due to curling (with opening density of 0.69 mm/m) potentially forming micro-cracks (0.014 mm-0.056 mm width) spaced at 20 mm-60 mm. Cracking at the top surface initiates from the beginning of drying, and stabilises after 180 days. Shrinkage cracking penetrates down to around a quarter of the slab thickness, and the tensile strength at the top surface reduces 50% of the maximum strength; whereas based on the Concrete Society TR34, the strength reduces by 30% at the surface and drops linearly to zero at half depth. The current study found that the stress induced by curling is dominant, compared to that induced by external restraints. Shrinkage induced cracks was found to reduce the ultimate load bearing capacity and the fatigue capacity of the pavement by up to 50%.
18
Incerti, Andrea. "Steel and macro-synthetic self-compacting fibre reinforced concrete, experimental study on the long-term deformations." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3265/.
Повний текст джерелаАнотація:
Experimental study on the long-term deformations of the fibre reinforced concrete.
Steel and macro-synthetic fibers were used to evaluate the shrinkage, creep, mid-span deflection, cracking and rupture analysis of three different types of samples.
At the end the main topics of ACI guidelines were analyzed in order to perform an overview of design.
19
Lewis, Kathryn R. "Fire Design of Steel Members." University of Canterbury. Civil Engineering, 2000. http://hdl.handle.net/10092/8279.
Повний текст джерелаАнотація:
The New Zealand Steel Code consists of few practical design tools other than finding the time and temperature that a simply supported steel member will fail. Many other design methods that consistently give accurate estimations of the behaviour of steel members have been published, and computer programmes developed to assist in the prediction of the temperature rise of steel when subjected to elevated temperatures environments.
This report describes the origins of the fire design methods used in the New Zealand
Steel Code, NZS 3404:1997. The New Zealand Steel Code is reviewed and the design features are compared with the equivalent method found in the Eurocode, ENV 1993-1-2, which is the most advanced international steel fire code.
The methods of evaluating the temperature rise of protected and unprotected steel beams are also investigated. Results from the simple formulas included in the New
Zealand Code, and those developed by the European Convention for Constructional
Steelwork, ECCS, are compared with results from the time step 'spreadsheet' method and from the finite element computer programme, SAFIR, for the ISO 834 standard fire. The comparisons show that the spreadsheet method gives temperatures very close to the average temperatures calculated by SAFIR for all cross sections and protection layouts. The equations from ECCS and NZS 3404 give good results for unprotected steel, and for protected steel the ECCS equations appear to represent the thermal response of the steel quite accurately while the New Zealand Steel Code has no simple method of estimating the temperatures for protected steel.
The methods used for comparing the results with the ISO fire are then repeated with
Eurocode Parametric fires, and with results from a real fire test.
Suggested improvements are made for the New Zealand Steel Code, to improve the concepts and information available to engineers designing for fire safety.
20
Kennedy, Gaylene Denise. "Repair of cracked steel elements using composite fibre patching." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0005/MQ34384.pdf.
Повний текст джерела
21
Nordström, Erik. "Durability of sprayed concrete : steel fibre corrosion in cracks /." Luleå, 2005. http://epubl.luth.se/1402-1544/2005/02.
Повний текст джерела
22
Elsaigh, Walied Ali Musa Hussien. "Modelling the behaviour of steel fibre reinforced concrete pavements." Pretoria : [s.n.], 2007. http://upetd.up.ac.za/thesis/available/etd-01292008-175515.
Повний текст джерела
23
Paine, Kevin Andrew. "Steel fibre reinforced concrete for prestressed hollow core slabs." Thesis, University of Nottingham, 1998. http://eprints.nottingham.ac.uk/11095/.
Повний текст джерелаАнотація:
An investigation of prestressed concrete containing steel fibres as secondary reinforcement to improve performance in shear, flexure and bond is reported. Emphasis is placed on the use of steel fibres in prestresssed extruded hollow core slabs, since these common precast elements have intrinsic difficulty in incorporating traditional secondary reinforcement due to their unique shape and manufacturing method. Two separate studies were carried out. The first study involved laboratory investigations into the bond between fibre reinforced concrete (FRC) and the prestressing strand, and the shear behaviour of laboratory-cast prestressed fibre reinforced concrete (PFRC) beams. The second part involved the factory production of fibre reinforced hollow core slabs in co-operation with a local manufacturer. The fibre reinforced hollow core slabs were subjected to conventional full-width shear tests, concentrated load shear tests, and to transverse flexure. For all laboratory cast elements, cubes, cylinders and prisms were cast to investigate compressive, tensile and flexural properties, respectively. Two types of steel fibre were investigated: hooked-end steel fibres at fibre volume fractions (Vf) of 0.5%, 1.0% and 1.5%; and amorphous metal fibres at Vf‘s of 0.28% and 0.56%. The trial production of fibre reinforced hollow core slabs necessitated the investigation of the effect of steel fibres on the extrusion manufacturing process. It was shown that fibre reinforced hollow core slabs could be adequately compacted with only slight increases in mixing water. Fibres were found to distribute randomly throughout the cross-section. However, the rotation of the augers affected the orientation of fibres, with fibres tending to align vertically in the web. It was shown that the addition of steel fibres to prestressed concrete has a negative effect on the bond between matrix and tendon, leading to longer transfer lengths. The effect of the increase in transfer length was to reduce cracking shear strengths by 4%. Shear tests showed that the incorporation of steel fibres could increase shear strength by as much as 45% for Vf = 1.5%. This increase in shear strength, known as the fibre contribution, was shown to be due to fibres bridging across the crack and an increased compressive resistance due to fibres arresting the propagation of cracks into the compressive zone. A semi-empirical equation for shear strength of PFRC elements is developed. It is given in two forms, one compatible with the present equations for prestressed concrete given in BS 8110 and Eurocode 2, and a second form compatible with that advocated for fibres in reinforced concrete. The equation makes use of equivalent flexural strength which is recognised as the most useful material property for design of FRC. The equation was found to give good correlation with the shear strength of single web beams cast both in the laboratory and under factory conditions. However, a overall strength reduction factor is required for full-width hollow core slabs to account for uneven load distribution and inconsistent web widths. This is consistent with tests on plain hollow core slabs found in the literature.
24
Oikonomou-Mpegetis, Sotirios. "Behaviour and design of steel fibre reinforced concrete slabs." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/23792.
Повний текст джерелаАнотація:
Using Steel Fibre Reinforced Concrete (SFRC) can bring substantial benefits to the construction industry of which savings in construction time and labour are most significant. In addition, steel fibres enhance crack control particularly when acting in conjunction with reinforcement bars. Despite the aforementioned benefits of SFRC, there is a still a lack of consensus on the principles that should be adopted in its design. Currently, a number of different test methods are used to determine the material properties of SFRC but there is no agreement on which method is best. As a result, steel fibre suppliers claim widely differing properties for similar fibres which leads to confusion amongst designers and in some cases inadequate structural performance. This research considers the design of SFRC slabs with emphasis on pile supported slabs which are frequently designed using proprietary methods due to the absence of codified guidance. Key issues in the design of such slabs are control of cracking in service and the calculation of flexural and punching shear resistances. A fundamental challenge is that SFRC exhibits a strain softening response at the dosages commonly used in slabs. At present, the yield line method is generally considered most suitable for designing such slabs at the ultimate limit state but there is a lack of consensus on the design moment of resistance as the bending moment along the yield lines reduces with increasing crack width. This thesis investigates these matters using a combination of experimental and theoretical work. The experimental work compares material properties derived from notched beam and round plate tests and seeks to determine a relationship between the two. Tests were also carried out on continuous slabs with the same material properties as used in the notched beam and round plate tests. Round plate tests were also carried out to determine the contribution of steel fibres to punching shear resistance. The theoretical work investigates the applicability of yield line analysis to the design of SFRC slabs using a combination of numerical modelling and design oriented analytical models. Design for punching shear and the serviceability limit state of cracking are also considered.
25
Mouton, Christiaan Johannes. "Investigating the tensile creep of steel fibre reinforced concrete." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20355.
Повний текст джерелаАнотація:
Thesis (MScEng)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Research in concrete has advanced to such an extent that it is now possible to add steel fibres to concrete in order to improve its durability and ductility. This led to a research group in Europe, FIB, who has provided guidelines to designing Steel Fibre Reinforced Concrete (SFRC) structures. They have found that it is possible for SFRC beams in flexure to be in static equilibrium. However, the time-dependent behaviour of SFRC has not been researched fully and it requires further investigation. When looking at a concrete beam in flexure there are two main stress zones, the compression zone and the tension zone, of which the tensile zone will be of great interest. This study will report on the investigation of the tensile time-dependent behaviour of SFRC in order to determine how it differs from conventional concrete. The concrete has been designed specifically to exhibit strain-softening behaviour so that the material properties of SFRC could be investigated fully. Factors such as shrinkage and tensile creep of SFRC were of the greatest importance and an experimental test setup was designed in order to test the tensile creep of concrete in a simple and effective manner. Comparisons were be made between the tensile creep behaviour of conventional concrete and SFRC where emphasis was placed on the difference between SFRC specimens before and after cracking occurred in order to determine the influence of steel fibre pull-out. The addition of steel fibres significantly reduced the shrinkage and tensile creep of concrete when un-cracked. It was however found that the displacement of fibre pull-out completely overshadowed the tensile creep displacements of SFRC. It was necessary to investigate what effect this would have on the deflection of SFRC beams in flexure once cracked. Viscoelastic behaviour using Maxwell chains were used to model the behaviour of the tensile creep as found during the tests and the parameters of these models were used for further analyses. Finite Element Analyses were done on SFRC beams in flexure in order simulate creep behaviour of up to 30 years in order to determine the difference in deflections at mid-span between un-cracked and pre-cracked beams. The analyses done showed that the deflections of the pre-cracked SFRC beams surpassed the requirements of the Serviceability Limit States, which should be taken into account when designing SFRC beams.
AFRIKAANSE OPSOMMING: Die navorsing in beton het gevorder tot so ‘n mate dat dit nou al moontlik is om staal vesels by die beton te voeg sodat dit beton se duursaamheid en duktiliteit te verbeter. Dit het gelei tot ‘n groep in Europa, FIB, wat dit moontlik gemaak het om Staal Vesel Beton (SVB) strukture te ontwerp. Hulle het gevind dat dit moontlik is vir SVB balke om in statiese ewewig te wees tydens buiging. Die tyd afhanklike gedrag van SVB is egter nog nie deeglik ondersoek nie en benodig dus verdure ondersoek. Wanneer ‘n balk in buiging aanskou word kan twee hoof spanningzones identifiseer word, ‘n druk zone en ‘n trek zone, waarvan die trek zone van die grootste belang is. Hierdie studie gaan verslag lewer oor die ondersoek van tyd-afhanklike trekgedrag van SVB om te bepaal hoe dit verskil van konvensionele beton. Die beton was spesifiek ontwerp om vervormingsversagtende gedrag te wat maak dat die materiaal eienskappe van SVB ten volle ondersoek kan word. Faktore soos krimp en die trekkruip van SVB was van die grootste belang en ‘n eksperimentele toets opstelling was ontwerp om die trekkruip van beton op ‘n eenvoudige en effektiewe manier te toets. Daar was vergelykings getref tussen die trekkruip gedrag van konvensionele beton en SVP en groot klem was geplaas op die verskil tussen SVB monsters voor en na die monsters gekraak het om te bepaal wat die invloed was van staalvesels wat uittrek. Die byvoeging van staalvesels het beduidend die kruip en trekkruip van beton verminder. Daar was alhoewel gevind dat die verplasing van die uittrek van staalvesels heeltemal die trekkruip verplasings van SVB oorskadu het. Dit was nodig om te sien watse effek dit op die verplasing van SVB balke in buiging sal hê. Viskoelastiese gedrag deur Maxwell kettings was gebruik om die gedrag van trekkruip, soos gevind deur die toetse, te modelleer en die parameters van hierdie modelle was verder gebruik vir analises. Eindige Element Analises was gedoen op SVB balke in buiging om die trekkruip gedrag tot op 30 jaar te simuleer op die verskil tussen die defleksies by midspan tussen ongekraakte en vooraf gekraakte balke te vind. Die analises het gewys dat die defleksies van die vooraf gekraakte balke nie voldoen het aan die vereistes van die Diensbaarheid limiete nie, wat in ag geneem moet word wanneer SVB balke ontwerp word.
26
Nordström, Erik. "Steel fibre corrosion in cracks : durability of sprayed concrete." Licentiate thesis, Luleå tekniska universitet, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18249.
Повний текст джерелаАнотація:
Steel fibre reinforced sprayed concrete is common practice for permanent linings in underground construction. Today there is a demand on "expected technical service life" of 120 years. Thin steel fibres could be expected to discontinue carrying load fast with a decrease of fibre diameter caused by corrosion, especially in cracks. The thesis contains results from inspections on existing sprayed concrete structures and a literature review on corrosion of steel fibres in cracked concrete. To study the mechanisms ruling inititation and propagation of corrosion both field exposure tests and accelerated laboratory exposure tests with cracked steel fibre reinforced sprayed concrete have been performed. Parameters tested are type of spraying method, exposure environment, fibre length, usage of accelerators, crack width and time of exposure. A discussion on how the influence of corrosion on load bearing capacity should be considered in a service-life model is also presented.Godkänd; 2000; 20070317 (ysko)
27
Ratner, Alon. "Hybrid steel wire strands with carbon fibre reinforced plastics." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/12477/.
Повний текст джерелаАнотація:
It has been hypothesised that weight reduction in ropes can be realised by the hybridisation of steel strands with non-metallic carriers in order to improve the efficiency of hoisting processes, most notably in mining applications. While this has been attempted by replacing steel central wires with unreinforced polymers and parallel fibre cores, this investigation has considered the replacement of steel wires with carbon fibre reinforced plastic rods. Fibre reinforced plastics are valued for their high strength-to-weight ratios and ubiquity. Since load sharing is maximal between materials of similar stiffness in a hybrid system, high strength carbon fibres were identified as the most feasible reinforcements for achieving compatible mechanical properties with those of high strength steel wires. A nylon polymer matrix was chosen to provide a reasonable balance between toughness, environmental stability and cost. A pultruder was designed and constructed in order to produce carbon fibre/nylon 12 rods for the creation of novel steel/CFRP hybrid strands. Development of the pultruder highlighted challenges in manufacturing that have been solved for industrial processes but remain underrepresented in academic research. Cost effective and flexible laboratory-scale techniques included fibre spreading by rollers, powder impregnation and the use of heating strips. Superior consolidation of the polymer matrix was obtained in rods pultruded from commingled stretch-broken carbon fibre/nylon tows, which emerged as the most appropriate feedstock. The Young's modulus and tenacity of hybrid carbon fibre/vinyl ester central rods were found to exceed that of standard steel strands, which in turn were higher than that of hybrid strands produced with in-house pultruded rods. Although this identified a need for the refinement of manufacturing conditions, it identified a lower bound of material properties required of the central rod in order to improve the tenacity of a hybrid strand. The finding of higher tenacity for the hybrid carbon fibre/vinyl ester strands demonstrated the feasibility of hybridising steel wire strands with non-metallic rods as a novel means of increasing the strength-to-weight ratio of strands. Finite element modelling of strands with a range of non-metallic core materials confirmed the material selection process by predicting the suitability of carbon fibre reinforced plastics over other core materials in improving the tenacity of hybrid strands.
28
Vieira, Mylene de Melo. "Assessment of chloride corrosion in steel fibre reinforced cementitious composites." Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/663458.
Повний текст джерелаАнотація:
High performance steel fibre reinforced cementitious composites (HPSFRCCs) show enhanced structural performance and durability. The improved properties favour its use in agressive conditions (such as marine environment) prone to corrosion. Despite the remarkable advances in the knowledge about corrosion of conventional reinforced concrete structures, questions still remain about its effects on the durability of HPSFRCC. The governing mechanisms of corrosion, the presence of cracks, the high steel fibre content, and the long-term chloride exposure still need to be properly evaluated. Given the increased application of HPSFRCC with structural responsibility and the high steel fibre content commonly used in the mixes, it is of great importance to understand the main mechanisms governing the chloride corrosion and its effects on the durability of the real-scale structures constructed with the material. To overcome these barriers and the uncertainty mentioned, this doctoral thesis adresses the following key issues: the effect of chlorides in uncracked HPSFRCCs under constant conditions; the influence of chloride corrosion in uncracked HPSFRCCs under wet-dry cycles with chlorides; the effect of corrosion in pre-cracked HPSFRCCs subjected to the same cycles and the proposal of a simplified model to consider the structural effects of corrosion. The first subject concerns the assessment of chloride corrosion on the aesthetic aspect and on the mechanical behaviour of HPSFRCCs by means of an accelerated test. For that, HPSFRCCs specimens with and without chlorides added to the mixes and with different fibre contents were tested. The preliminary experimental programme shows that, in general, the chlorides produce a level of surface corrosion with aesthetic consequences but have small influence on the mechanical performance. In the second subject, the influence of cycles was assessed in accelerated tests with uncracked HPSFRCCs prisms. The results reveal that, for uncracked HPSFRCCs elements, the corrosion affects the surface aspect but has no influence on the post-cracking response. The third subject focuses on the analysis of pre-cracked HPSFRCCs prisms under cyclic chloride exposure, considering different pre-crack widths and fibre contents. The study shows that the corrosion affects significantly the mechanical behaviour of the fibres for all specimens. The last subject covers a proposal of a simplified model to consider the effect of corrosion in the ULS design of HPSFRCC elements under cyclic chloride exposure. The model proposed was capable of reproducing the influence of the corrosion process over the cycles, being compatible with the current philosophy proposed in codes for the design of HPSFRCC structures.Los compuestos cementicios de alta resistencia reforzados con fibra de acero (CCARRFA) muestran un mayor rendimiento estructural y durabilidad. Las mejoras en las propiedades del CCARRFA debido a la inclusión de fibras de acero favorecen su uso en condiciones agresivas (tales como el ambiente marino) propensas a la corrosión. A pesar de los notables avances en el estudio de la corrosión de estructuras de hormigón armado, aún quedan cuestiones sin resolver respecto a sus efectos en la durabilidad del CCARRFA. En relación a ello, los mecanismos que gobiernan la corrosión, la presencia de fisuras, el alto contenido de fibra de acero y la exposición prolongada a los cloruros deben ser evaluados adecuadamente. Dado el aumento de la utilización de CCARRFA con responsabilidad estructural y el alto contenido de fibra de acero comúnmente utilizado en las mezclas, resulta de gran importancia comprender los principales mecanismos que gobiernan la corrosión, así como sus efectos en la durabilidad de estructuras a escala real construidas con este material. Para superar estas barreras y las incertidumbres mencionadas, esta tesis doctoral tratará los siguientes aspectos clave: el efecto de los cloruros en CCARRFA no fisurado en condiciones constantes; la influencia de la corrosión por cloruros en CCARRFA no fisurado sometido a ciclos de mojado y secado con cloruros; el efecto de la corrosión en CCARRFA fisurados sometidos a los mismos ciclos y una propuesta de modelo simplificado para considerar los efectos estructurales de la corrosión. El primer aspecto aborda la evaluación de la corrosión por cloruros desde un punto de vista estético y del comportamiento mecánico del CCARRFA mediante un ensayo acelerado. Para ellos, se han ensayado probetas de CCARRFA con y sin cloruros añadidos a las mezclas con diferentes contenidos de fibra. La campaña experimental preliminar mostró que, en general, los cloruros producen un nivel de corrosión superficial con consecuencias estéticas, pero con poca influencia en el comportamiento mecánico. En el segundo aspecto, se evaluó la influencia de los ciclos en ensayos acelerados en probetas de CCARRFA no fisuradas. Los resultados revelaron que en los elementos de CCARRFA no fisurados la corrosión afecta al aspecto superficial pero no influye en la respuesta post-fisuración. El tercer aspecto trata el análisis de probetas de CCARRFA fisuradas con diferentes anchos de fisura y contenidos de fibra sometidas a una exposición cíclica de cloruros. El estudio muestra que la corrosión afecta significativamente al comportamiento mecánico de las fibras de todas las probetas. El último aspecto se centra en la propuesta de uno modelo simplificado que considera el efecto de la corrosión en el diseño en ELU de elementos de CCARRFA bajo una exposición cíclica de cloruros. El modelo propuesto es capaz de reproducir el efecto del proceso de la corrosión a lo largo de los ciclos, siendo compatible con la actual filosofía propuesta en códigos para el diseño de estructuras de CCARRFA.
29
Smith, Joel Aaron. "Implosion of steel fibre reinforced concrete cylinders under hydrostatic pressure." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0001/MQ45939.pdf.
Повний текст джерела
30
Sarandily, A. "High strength autoclaved cementitious matrices and steel fibre reinforced composites." Thesis, University of Salford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374519.
Повний текст джерела
31
Kennedy, I. "Vibration transmissibility characteristics of fibre and steel reinforced flexible pipes." Thesis, University of Manchester, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378334.
Повний текст джерела
32
Shortall, Christopher Douglas. "Mechanical characterisation of an isotropic stainless steel fibre network material." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611295.
Повний текст джерела
33
Molloy, Brian T. "Steel fibre and rebar corrosion in concrete under marine curing." Thesis, University of Aberdeen, 1990. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU032222.
Повний текст джерелаАнотація:
Concern for durability of reinforced concrete structures has, in recent years, coincided with an increasing interest in the use of steel fibre reinforcement. In this investigation the corrosion behaviour of conventional and steel fibre reinforcement in concrete under long term marine curing have been studied. The corrosion behaviour of reinforcement has been assessed visually, and by using electrochemical techniques. Three types of steel fibre were investigated namely low carbon steel, stainless steel melt extract, and galvanised steel. Previous studies have shown that steel fibres exhibit good corrosion resistance in concrete exposed to marine curing. It has been suggested that this is due to the discrete nature of the individual steel fibres which prevents the development of electrochemical cells with large cathode/anode area ratios. In order to determine, therefore, whether a 'size-effect' phenomenon influences steel fibre corrosion rates, concrete specimens were cast with different lengths and diameters of steel wire and subsequently exposed to marine curing. Parallel concrete specimens containing samples of conventional reinforcing bar were also manufactured. Cement replacement materials such as pulverised fuel ash, ground granulated blast furnace slag and microsilica are widely used in order to enhance specific properties of fresh or hardened concrete. In this investigation durability characteristics of concrete containing cement replacement materials were studied. These characteristics, including alkalinity of pore fluid and diffusion rates of chloride ions are of importance in relation to the passivation or corrosion of steel reinforcement.
34
Lasota, Tomáš. "Computational Modelling of Mechanical Behaviour of "Elastomer-Steel Fibre" Composite." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-234188.
Повний текст джерелаАнотація:
Tato práce se zabývá výpočtovými simulacemi zkoušek jednoosým tahem a tříbodovým ohybem kompozitního vzorku složeného z elastomerové matrice a ocelových výztužných vláken orientovaných pod různými úhly, jakož i jejich experimentální verifikací. Simulace byly provedeny pomocí dvou různých modelů - bimateriálového a unimateriálového výpočtového modelu. Při použití bimateriálového modelu, který detailně zohledňuje strukturu kompozitu, tzn. pracuje s matricí a jednotlivými vlákny, je zapotřebí vytvořit model každého vlákna obsaženého v kompozitu, což přináší řadu nevýhod (pracná tvorba výpočtového modelu, řádově větší množství elementů potřebných k diskretizaci v MKP systémech a delší výpočetní časy). Na druhé straně v unimateriálovém modelu se nerozlišují jednotlivá vlákna, pracuje se pouze s kompozitem jako celkem tvořeným homogenním materiálem a výztužný účinek vláken je zahrnut v měrné deformační energii. Porovnání experimentů se simulacemi ukázalo, že bimateriálový model je v dobré shodě s experimenty, na rozdíl od unimateriálového modelu, který je schopen poskytnou odpovídající výsledky pouze v případě tahového namáhání. Z tohoto důvodu byl hledán způsob, který by umožnil rozšířit unimateriálový model o ohybovou tuhost výztužných vláken. V roce 2007 Spencer a Soldatos publikovali rozšířený unimateriálový model, který je schopen pracovat nejen s tahovou, ale i ohybovou tuhostí vlákna. Představený obecný model je však založen na Cosseratově teorii kontinua a jeho praktické využití je pro jeho složitost nemožné. Proto byl vytvořen zjednodušený model (částečně podle Spencera a Soldatose) s vlastní navrženou formou měrné deformační energie. Za účelem ověření nového unimateriálového modelu s ohybovou tuhostí vláken byly odvozeny všechny potřebné rovnice a byl napsán vlastní konečno-prvkový řešič. Tento řešič je založen na Cosseratově teorii kontinua a obsahuje zmíněný anizotropní hyperelastický unimateriálový model zahrnující ohybovou tuhost vláken. Vzhledem k tomu, že v případě Cosseratovy teorie jsou při výpočtu potřebné i druhé derivace posuvů, bylo nutné použít tzv. C1 prvky, které mají spojité jak pole posuvů, tak jejich prvních derivací. Nakonec byly provedeny nové simulace s využitím vlastního řešiče, které ukazují, že tuhost vláken lze u nového unimateriálového modelu řídit odpovídající materiálovou konstantou. V závěru práce je pak diskutováno, zda je nový unimateriálový model s ohybovou tuhostí schopen poskytnout stejné výsledky jako model bimateriálový, a to jak při tahovém tak i ohybovém namáhání kompozitního vzorku.
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Elsaigh, W. A. "Steel fiber reinforced concrete ground slabs : a comparative evaluation of plain and steel fiber reinforced concrete ground slabs." Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-03032006-154355/.
Повний текст джерела
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Algassem, Omar. "Parameters Affecting the Blast Performance of High Strength Fibre Reinforced Concrete Beams." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35022.
Повний текст джерелаАнотація:
A limited number of studies have been conducted in the literature in order to investigate the behaviour of high-strength fibre-reinforced concrete (HSFRC) structural components subjected to blast loads. This study summarizes the results of a research program investigating the potential of using steel fibres to improve the blast performance of high-strength reinforced concrete beams. As part of the experimental investigation twenty beams were tested, including nine beams tested under static four-point bending, and eleven beams tested under dynamic blast loads using a shock-tube. Parameters considered in the study include the effect of concrete strength, steel fibres, fibre content, fibre type, longitudinal reinforcement ratio, and presence of shear reinforcement. All beams in the study have identical dimensions, with a cross-section of 125 x 250 mm and length of 2440 mm. To manufacture the specimens, two beams were cast with normal-strength self-consolidate concrete (SCC), with a specified strength of 50 MPa, while the remaining beams were cast with either plain or fibre-reinforced high-strength concrete having a compressive strength which varied between 95-110 MPa. The steel fibre content in the HSFRC beams varied between 0.5 and 1.0%, by volume of concrete. To investigate the effect of reinforcement ratio (ρ), the beams were reinforced with 2-#4 (American size) bars, 2-15M bars or 2-20M bars (ρ = 1.02%, 1.59%, and 2.41%, respectively). The majority of the plain concrete beams had transverse reinforcement which consisted of 6 mm stirrups arranged at a spacing of 100 mm in the shear spans, while most of the HSFRC beams were built without stirrups. The results indicate that all the parameters in this study (reinforcement ratio, presence of stirrups, concrete strength, steel fibres, fibre content and fibre type) affected the static and blast response of the beams, however, the results demonstrate that steel fibres have a more remarkable effect when compared to the other parameters. The provision of fibres is found to improve the blast performance of the HSC beams by increasing shear capacity, reducing maximum and residual mid-span displacements, reducing blast fragments and increasing damage tolerance.
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Olawale, Aderemi Olayiwola. "Collapse behaviour of steel columns in fire." Thesis, University of Sheffield, 1988. http://etheses.whiterose.ac.uk/1869/.
Повний текст джерелаАнотація:
The three years' work undertaken in this project is a purely numerical analysis of the inelastic behaviour of steel columns in fire. This is made up of three main parts, each devoted to the development and use of a numerical technique to study the behaviour of steel columns in fire. The first two chapters report on the state of the art on plate analysis, plasticity theories, column behaviour at room temperature, finite strip method and the behaviour of columns at elevated temperature. Part 1, consisting of Chapters 3 to 5, reports on the development of the small deflection finite strip method which includes the effect of plastification of component plates using deformation theory of plasticity. The validity of the method is tested by comparing with published test data on steel columns at ambient and elevated temperature. The comparisons show that the method gives good correlation with test data. Parametric studies have been carried out to assess the effects of slenderness ratios, different stress-strain-temperature representations, residual stresses, eccentricity of loading and local budding of columns. In addition the inelastic behaviour of an H-section under uniform end couples is studied. Part 2, consisting of Chapters 6 and 7, reports on the development of a finite element method which includes the effect of thermal gradients over the member cross-section. The method is compared with test data on both uniformly and non-uniformly heated columns. This shows a good correlation between the method and experiment. Parametric studies have been carried out to assess the effects of initial out-of-straightness, different end conditions, thermal gradients and interaction of eccentricity of loading with thermal gradients on columns. In addition a simple Shanley's column theory is utilised to demonstrate the interaction effect of eccentricity of loading with thermal gradients on columns. Part 3, consisting of Chapter 8, reports on the development of a large deflection finite strip method which includes flow theory of plasticity. The method has not been used for any parametric study. Finally, general conclusions and recommendations for future works are presented in Chapter 9. It is hoped that the valuable information provided in this thesis will be useful in providing a better understanding on the real behaviour of steel columns in fire.
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Abu, Sha'ari. "Analysis of steel frame structures in fire." Thesis, University of Sheffield, 1991. http://etheses.whiterose.ac.uk/3065/.
Повний текст джерелаАнотація:
The main aim of the present research is to develop a method of analysis for structural frames exposed to fire including the effects of material and geometric non-linearities. A matrix stiffness method based on a secant stiffness approach is used providing a full temperature deformation history. The approach has previously been used for the analysis of continuous beams and is extended in the present work to include axial forces. These not only affect the longitudinal displacement, but also reduce the member stiffness and create secondary moments due to the p-delta effect. The influence of material unloading on the moment-axial force-curvature relationship is studied by examining a cross-section subjected to different combinations of bending moment and axial force at both ambient temperature and in fire. A computer program, based on the method is used to conduct a limited parametric study. This includes the influence of slenderness ratio, the magnitude of axial load and moment, the size of cross-section and grade of steel. Both uniform and non-uniform temperature profiles are considered for isolated beams, columns and simple portal frame. The importance of the p-delta effect is also investigated.
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Cheng, Shanshan. "Fire performance of cold-formed steel sections." Thesis, University of Plymouth, 2015. http://hdl.handle.net/10026.1/3316.
Повний текст джерелаАнотація:
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.
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Ramli, Sulong Nor Hafizah. "Behaviour of steel connections under fire conditions." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424307.
Повний текст джерела
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Ramli, Sulong Nor Hafizah. "Behaviour of steel connections under fire conditions." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424307.
Повний текст джерела
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Pros, Parés Alba. "Numerical approach for modeling steel fiber reinforced concrete." Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/83724.
Повний текст джерелаАнотація:
One alternative to overcome the main drawbacks of plain concrete in tension (its brittleness and weakness) is Steel Fiber Reinforced Concrete (SFRC), a technique introduced in the 70's, which consists of adding steel fibers into the concrete matrix.
Due to the presence of the steel fibers into the concrete matrix, the residual strength and the energy dissipation of the material increase. Moreover, once a crack appears in the concrete, the steel fibers sew this fissure. The shape, the length and the slenderness of the fibers influence on the SFRC behavior. Moreover, the distribution and the orientation of the fibers into the concrete domain must be taken into account for characterizing the material.
In order to characterize the behavior of SFRC, a numerical tool is needed. The aim is to simulate the most standard and common tests (direct and indirect tension tests, flexural test, double punch tes,¿) and more complex setups.
This thesis proposes a numerical tool for modeling SFRC avoiding homogenized models (not accurate enough) and conformal meshes (too expensive). Therefore, the numerical tool accounts for the actual geometry of the fibers, discretized as 1D bars nonconformal with the concrete bulk mesh (2D or 3D domains). The two materials, corresponding to the concrete bulk and the fiber cloud, are defined independently, but coupled by imposing displacement compatibility. This compatibility is enforced following the ideas of the Immersed Boundary methods.
Two different models are considered for modeling the concrete bulk (a continuous one and a discontinuous one). The parametric study of each model is done for only plain concrete, before the addition of the steel fibers.
A phenomenological mesomodel is defined for modeling steel fibers, on the basis of the analytical expressions describing the pullout tests. This phenomenological mesomodel not only describes the behavior of the steel fibers, but also accounts for the concrete-fiber interaction behavior. For each fiber, its constitutive equation is defined depending on its shape (straight or hooked) and the angle between the fiber and the normal direction of the failure pattern.
Both 2D and 3D examples are reproduced with the proposed numerical tool. The obtained results illustrate the presence of the steel fibers into the concrete matrix. The shape of the fiber influences of the SFRC behavior: the residual strength is higher for hooked fibers than for straight ones. Moreover, increasing the quantity of fibers means increasing the residual strength of the material.
The obtained numerical results are compared to the experimental ones (under the same hypothesis). Therefore, the proposed numerical approach of SFRC is validated experimentally.
43
Belghiti, Moulay El Mehdi. "Influence of steel fibres on response of beams." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100222.
Повний текст джерелаАнотація:
The following thesis presents the results of six full scale beams tests as part of a research program conducted at McGill University on the effect of steel fibres on the shear capacity of a beam with an aid ratio greater than 2.5. The test specimens had the following dimensions: 4400 mm long, 300 mm wide and 500 mm long. The beams had 4-25M bottom reinforcing bars and 2-20M top reinforcing bars. Two series were designed with different reinforcing details: the "BA" series contained transverse reinforcement spaced at 275 mm center to center while the "BB" series had no transverse reinforcement. The specimens were cast in three batches of two specimens from each series, with each batch containing concrete with respectively 0%, 0.5% and 1% fibres content by volume. The beams were simply supported and were tested with two equal point loads located at 500 mm from the centre of the beam.This research project demonstrated a clear improvement of the shear capacity resulting from the use of steel fibres for the beams without transverse reinforcement. For the beams with transverse reinforcement, displacement ductility was highly increased. This suggests that fibres have the potential to reduce the congestion of the reinforcement if fibres are designed to replace partially closely spaced transverse reinforcement. Also, it was noted that a redistribution of stresses occurred resulting in the formation of more well-controlled cracks. Finally, the strength predictions using the method developed by Aoude (Aoude, 2007) agree very well with the experimental results.
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Bam, T. J. "A computer-based justification for using the simple bend test as the basis for predicting the performance of steel hooked-end fibres in reinforced concrete." Diss., University of Pretoria, 2019. http://hdl.handle.net/2263/75657.
Повний текст джерелаАнотація:
The classical test to confirm the performance of a given fibre design for use in reinforced concrete is the pull-out test. While attempts have been made to simulate the performance of such pull-out tests, in practice it has been found that there is a significant disparity between prediction and real-life performance.
The high strength of steel reinforcing fibres is a consequence of the cold wire drawing process and subsequent fabrication. Residual stresses exist in cold drawn wire as a consequence of the elastic response to a non-uniform distribution of plastic strain. This also introduces a yield strength profile where yield strength varies radially through the wire. The question arises as to whether fibre design should use a starting material model that considers these properties.
This thesis examines whether the tensile test, simple bend test and pull-out test provide enough information to define a starting material model that may be used for further design and simulation of such fibres.
Since the details of the wire drawing process and material specification are proprietary and therefore unknown, a sensitivity study was conducted to determine which aspects of the wire drawing process have the greatest effect on the pull-out curve and the following were established as being significant:
• Plastic strain due to wire drawing was shown to be the most important factor.
• The bilinear curve was shown to be a suitable approximation for the stress-strain curve.
• Replacing the plastic strain profile with a single value of average equivalent plastic strain is practical.
The following were established as having negligible effect:
• The consequences of the hooked-end forming process.
• The residual stress profiles due to wire drawing provided that the above was also excluded.
• The hardening law
While inverse analysis demonstrated that all tests provide sufficient information to determine the required properties for this bilinear material model, the pull-out test was shown to provide more accurate approximations of the maximum pull-out force at the first and second peaks and the bend test was shown to produce more accurate approximations of the energy associated with pull-out. Good correlation with the baseline pull-out curve was found for both the isotropic and the kinematic hardening laws and it is concluded that behaviour during pull-out is insensitive to the hardening law.
Sensitivity analysis and characterisation of the material model using an experimental pull-out curve demonstrated the importance of the coefficient of friction. Full characterisation using the pull-out curve therefore requires the solution to a three-variable problem: yield strength, tangent modulus and coefficient of friction. This was a suggested topic for further study.Dissertation (MEng)--University of Pretoria, 2019.
Mechanical and Aeronautical Engineering
MEng (Mech)
Unrestricted
45
Kadhim, Majid. "Dynamic response of structural steel elements post-strengthened with CFRP." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/dynamic-response-of-structural-steel-elements-poststrengthened-with-cfrp(6e71c4d5-0bc5-4274-bd84-f99b0c966bb1).html.
Повний текст джерелаАнотація:
Structural elements in buildings and civil engineering infrastructure can often be vulnerable to various kinds of impact actions during their service life. These actions could result from various sources e.g. collision of vehicles, ships and vessels or falling masses in industrial buildings. Since, for various reasons, such accidental actions have not always been considered in the existing engineering design of buildings and civil engineering structures such as bridges etc., investigation of effective structural strengthening techniques is justified. As fibre reinforced polymer (FRP) composites have commonly been employed efficiently to strengthen steel members against static and fatigue loads, examining the FRP strengthening technique to enhance structural steelwork in impact situations is the main focus of this study. The research aims to experimentally investigate the dynamic behavioural response of axially loaded steel columns and steel beams strengthened with various carbon fibre reinforced polymer (CFRP) configurations. To achieve this goal, a series of experimental tests was implemented including testing a number of CFRP strengthened and unstrengthened steel beams and columns under static and impact loads. The experimental results show that CFRP can improve the global and local behaviour of steel members subjected to impact loads. This improvement varied depending on the CFRP configuration, the amount of CFRP and the pre-existing axial load value in the member. In order to examine all the parameters that can affect the dynamic behaviour of CFRP strengthened steel members in addition to those not included in the experimental programme, a comprehensive numerical simulation of the experimental work was carried out using a validated finite element model. Afterwards, an extensive parametric study was conducted to provide a comprehensive understanding of the behaviour of CFRP strengthened steel members subjected to impact load. The simulation results illustrate that the effectiveness of CFRP increases with high impact energies. The parametric study results have also revealed that the configurations and distributions of CFRP have a major influence on the effectiveness of the reinforcement. A detailed numerical assessment has also been performed to find the CFRP effectiveness when applied to full-scale steel columns. It has been found that strengthening with CFRP in practical quantities and configurations could prevent steel columns from failure under transverse impact loading. The strengthening effectiveness was found to be dependent on boundary conditions, impact velocity, impact mass, impact location, preloading level, impact direction, CFRP configuration, and the length and thickness of the CFRP. Based on the results obtained from the full-scale simulation, it has been found that the CFRP strengthening technique can be used efficiently and effectively at the scale of elements common in everyday building and infrastructure. This study also provides a useful database for different kinds of strengthening configurations, impact velocities and masses, boundary conditions, etc.
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Collette, Kristin A. "Comparisons of structural designs in fire." Link to electronic thesis, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-050307-182832/.
Повний текст джерелаАнотація:
Thesis (M.S.) -- Worcester Polytechnic Institute.Keywords: Office buildings; Steel beams; Lumped parameter method; Cardington Tests; Design fire curves . Includes bibliographical references (leaves 144-146).
47
Levchuk, Svetlana. "Interface development for a EUROFER steel matrix composite with SiC-fibre reinforcement." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=97895694X.
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Mondo, Eleonora. "Shear Capacity of Steel Fibre Reinforced Concrete Beams without Conventional Shear Reinforcement." Thesis, KTH, Bro- och stålbyggnad, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-41016.
Повний текст джерелаАнотація:
While the increase in shear strength of Steel Fibre Reinforced Concrete (SFRC) is well recognized, it has yet to be found common application of this material in building structures and there is no existing national standard that treats SFRC in a systematic manner. The aim of the diploma work is to investigate the shear strength of fibre reinforced concrete beams and the available test data and analyse the latter against the mostpromising equations available in the literature. The equations investigated are:Narayanan and Darwish’s formula, the German, the RILEM and the Italian guidelines. Thirty articles, selected among over one hundred articles taken from literature, have been used to create the database that contains almost 600 beams tested in shear. This large number of beams has been decreased to 371 excluding all those beams and test that do not fall within the limitation stated for this thesis. Narayanan and Darwish’s formula can be utilized every time that the fibre percentage, the type of fibres, the beam dimensions, the flexural reinforcement and the concrete strength class have been defined. On the opposite, the parameters introduced in the German, the RILEM and the Italian guidelines always require a further characterization of the concrete (with bending test) in order to describe the post‐cracking behaviour. The parameters involved in the guidelines are the residual flexural tensile strengths according to the different test set‐ups. A method for predicting the residual flexural tensile strength from the knowledge of the fibre properties, the cylindrical compressive strength of the concrete and the amount of fibres percentage is suggested. The predictions of the shear strength, obtained using the proposed method for the residual flexural tensile strength, showed to be satisfactory when compared with the experimental results. A comparison among the aforementioned equations corroborate the validity of the empirical formulations proposed by Narayanan and Darwish nevertheless only the other equations provide a realistic assessments of the strength, toughness and ductility of structural elements subjected to shear loading. Over the three investigated equations, which work with the post‐cracking characterization of the material, the Italian guideline proposal is the one that, due to its wide domain of validity and the results obtained for the gathered database of beams, has been selected as the most reliable equation.
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Kolle, Boris. "Behaviour of steel fibre reinforced high performance concrete under biaxial loading conditions." Thesis, University of Glasgow, 2006. http://theses.gla.ac.uk/715/.
Повний текст джерелаАнотація:
This thesis includes an experimental investigation of the behaviour of steel fibre reinforced high performance concrete (SFRHPC) under biaxial loading conditions. Also included are constitutive models to enable numerical predictions of the strength behaviour of such a material. Within the experimental stage a large biaxial test machine was designed and manufactured. The load capacity of each axis was 2000 kN. Special thought was given to the load platen system because of the friction which occurs between the platen system and the concrete specimen. Brush bearing platens and solid steel blocks with and without Teflon friction reducing pads were tried. Because the brush platen and the Teflon pads were constantly damaged during testing, solid steel block platens were finally used. For tests where tension loads were involved, experiments were carried out with dog-bone shaped specimens and specimens glued on to the platens. Finally, the tension loads were transferred through threaded rods cast into the specimens and connected to the machine patterns with screws. Modern control schemes and high speed data acquisition systems were used to monitor the material response and to collect experimental stress and strain results. The principal deformations were monitored and the crack patterns and failure modes examined. Failure envelopes were developed based on the strength data for each fibre variable. The load capacity of SFRHPC under biaxial load conditions was found to be larger than for plain HPC for all fibre types and volume fractions. The stress-strain recordings indicated a linear behaviour almost up to failure. The examined failure mode between plain and steel fibre HPC was similar and all specimens failed very suddenly with a splitting failure type. The test variables included four different types of hooked ended steel fibres with different fibre volume fractions from plain to 2% in 0.5% steps. The specimens were tested under the entire range of stress combinations including uniaxial compression and tension and biaxial compression-compression and compression-tension. As a result the specimen still failed in an explosive manner but the pieces were still connected together by fibres after failure. The biaxial strength compared to the uniaxial strength increased more, as observed with normal strength concrete. With the addition of fibres the biaxial strength behaviour of HPC was almost the same as for plain normal strength concrete. The deformation characteristics of plain and SFRHPC showed a linear behaviour up to a higher stress than normal strength concrete. In fact the linear limit was almost as high as the failure load. The examined strength data was used to model the biaxial strength envelopes of HPC and SFRHPC using different methods. These included the Ottosen failure criterion and the Willam and Warnke failure criterion.
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Islam, S. M. Zahurul. "Strengthening of aluminium and stainless steel tubular sections with fibre-reinforced polymer." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B47752865.
Повний текст джерелаАнотація:
Strengthening of aluminium and stainless steel structural tubular sections using
adhesive bonded fibre-reinforced polymer (FRP) subjected to web crippling has been
investigated. Aluminium and stainless steel tubular sections may experience web
crippling failure due to local concentrated loads or reactions. The web crippling
strength can be enhanced by strengthening the webs of the sections in localized
regions. The current international specifications of aluminium and stainless steel
structures do not provide web crippling design rules for strengthening of tubular
sections. Therefore, there is a need to develop safe and reliable web crippling design
rules for FRP strengthened aluminium and stainless steel structures.
An extensive test program was performed on FRP strengthening of aluminium and
cold-formed stainless steel tubular sections subjected to web crippling. The test
specimens consisted of 6061-T6 heat-treated aluminium alloy, ferritic stainless steel
type EN 1.4003 and lean duplex type EN 1.4162 square and rectangular hollow
sections. A total of 254 web crippling tests was conducted in this study. The tests
were performed on eighteen different sizes of tubular sections which covered a wide
range of web slenderness (flat portion of web depth-to-thickness) ratio from 6.2 to
62.2.
The web crippling tests were conducted under the four loading conditions according
to the American Specification and Australian/New Zealand Standard for cold-formed
steel structures, namely End-Two-Flange, Interior-Two-Flange, End-One-Flange and
Interior-One-Flange loading conditions. The investigation was mainly focused on the
effects of different adhesive, FRP, surface treatment, widths of FRP plate and web
slenderness of tubular sections for strengthening against web crippling. Six different
adhesives, six different FRPs, two different surface treatments, three different widths
of FRP plate were considered. It was found that the web crippling capacity of
aluminium tubular sections are significantly increased due to FRP strengthening,
especially for those sections with large value of web slenderness. The web crippling
strength can be increased up to nearly 3 times using the appropriate adhesive and
FRP for aluminium tubular sections, whereas the web crippling strength can be
increased up to 51% and 76% for ferritic and lean duplex stainless steel tubular
sections, respectively.
The finite element models for FRP strengthened aluminium and stainless steel
tubular structural members subjected to web crippling were developed and calibrated
against the experimental results. The debonding between FRP plate and aluminium
or stainless steel tubes was carefully modelled using cohesive element. It is shown
that the calibrated model closely predicted the web crippling strengths and failure
modes of the tested specimens. An extensive parametric study included 212 web
crippling specimens was carried out using the verified finite element models to
examine the behaviour of strengthened aluminium and stainless steel tubular sections
subjected to web crippling.
Design equations are proposed to predict the web crippling strengths of FRP
strengthened aluminium and stainless steel tubular sections based on the
experimental and numerical results. The web crippling strengths obtained from the
tests and numerical analysis were compared with the design strengths calculated
using the proposed equations. The reliability of the proposed design rules was
evaluated using reliability analysis.published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy