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Mitchell, Andrew Douglass. "Shear friction behavior of high-strength concrete." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/19274.
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Zaina, Mazen Said Civil & Environmental Engineering Faculty of Engineering UNSW. "Strength and ductility of fibre reinforced high strength concrete columns." Awarded by:University of New South Wales. School of Civil and Environmental Engineering, 2005. http://handle.unsw.edu.au/1959.4/22054.
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The main structural objectives in column design are strength and ductility. For higher strength concretes these design objectives are offset by generally poor concrete ductility and early spalling of the concrete cover. When fibres are added to the concrete the post peak characteristics are enhanced, both in tension and in compression. Most of the available experimental data, on fibre reinforced concrete and fibre reinforced high strength concrete columns, suggest that an improvement in both ductility and load carrying capacity due to the inclusion of the fibres. In this thesis the ductility and strength of fibre reinforced high strength concrete are investigated to evaluate the effect of the different parameters on the performance of columns. The investigation includes both experimental and the numerical approaches with 56 high strength fibre reinforced concrete columns being tested. The concrete strength ranged between 80 and 100 MPa and the columns were reinforced with 1, 2 or 2.6 percent, by weight, of end hooked steel fibres. The effect of corrugated Polypropylene fibres on the column performance was also examined. No early spalling of the cover was observed in any of the steel fibre reinforced column tested in this study. A numerical model was developed for analysis of fibre and non-fibre reinforced eccentrically loaded columns. The column is modelled as finite layers of reinforced concrete. Two types of layers are used, one to represent the hinged zone and the second the unloading portion of the column. As the concrete in the hinged layers goes beyond the peak for the stress verus strain in the concrete the section will continue to deform leading to a localised region within a column. The numerical model is compared with the test data and generally shows good correlation. Using the developed model, the parameters that affect ductility in fibre-reinforced high strength concrete columns are investigated and evaluated. A design model relating column ductility with confining pressure is proposed that includes the effects of the longitudinal reinforcement ratio, the loading eccentricity and the fibre properties and content and design recommendations are given.
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Yosefani, Anas. "Flexural Strength, Ductility, and Serviceability of Beams that Contain High-Strength Steel Reinforcement and High-Grade Concrete." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4402.
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Utilizing the higher capacity steel in design can provide additional advantages to the concrete construction industry including a reduction of congestion, improved concrete placement, reduction in the required reinforcement and cross sections which would lead to savings in materials, shipping, and placement costs. Using high-strength reinforcement is expected to impact the design provisions of ACI 318 code and other related codes.
The Applied Technology Council (ATC-115) report "Roadmap for the Use of High-Strength Reinforcement in Reinforced Concrete Design" has identified key design issues that are affected by the use of high-strength reinforcement. Also, ACI ITG-6, "Design Guide for the Use of ASTM A1035 Grade 100 Steel Bars for Structural Concrete" and NCHRP Report 679, "Design of Concrete Structures Using High-Strength Steel Reinforcement" have made progress towards identifying how code provisions in ACI 318 and AASHTO could be changed to incorporate high-strength reinforcement.
The current research aims to provide a closer investigation of the behavior of beams reinforced with high-strength steel bars (including ASTM A615 Grade 100 and ASTM A1035 Grades 100 and 120) and high-strength concrete up to 12000 psi. Focus of the research is on key design issues including: ductility, stiffness, deflection, and cracking.
The research includes an extensive review of current literature, an analytical study and conforming experimental tests, and is directed to provide a number of recommendations and design guidelines for design of beams reinforced with high-strength concrete and high-strength steel. Topics investigated include: strain limits (tension-controlled and compression-controlled, and minimum strain in steel); possible change for strength reduction factor equation for transition zone (Φ); evaluation of the minimum reinforcement ratio (þmin); recommendations regarding limiting the maximum stress for the high-strength reinforcement; and prediction of deflection and crack width at service load levels. Moreover, this research includes long-term deflection test of a beam made with high grade concrete and high-strength steel under sustained load for twelve months to evaluate the creep deflection and to insure the appropriateness of the current ACI 318 time-dependent factor, λ, which does not consider the yield strength of reinforcement and the concrete grade.
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Dabbagh, Hooshang Civil & Environmental Engineering Faculty of Engineering UNSW. "Strength and ductility of high-strength concrete shear walls under reversed cyclic loading." Awarded by:University of New South Wales. School of Civil and Environmental Engineering, 2005. http://handle.unsw.edu.au/1959.4/27467.
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This study concerns the strength and behaviour of low-rise shear walls made from high-strength concrete under reversed cyclic loading. The response of such walls is often strongly governed by the shear effects leading to the shear induced or brittle failure. The brittle nature of high-strength concrete poses further difficulties in obtaining ductile response from shear walls. An experimental program consisting of six high-strength concrete shear walls was carried out. Specimens were tested under inplane axial load and reversed cyclic displacements with the test parameters investigated being longitudinal reinforcement ratio, transverse reinforcement ratio and axial load. Lateral loads, lateral displacements and the strains of reinforcement in edge elements and web wall were measured. The test results showed the presence of axial load has a significant effect on the strength and ductility of the shear walls. The axially loaded wall specimens exhibited a brittle behaviour regardless of reinforcement ratio whereas the specimen with no axial load had a lower strength but higher ductility. It was also found that an increase in the longitudinal reinforcement ratio gave an increase in the failure load while an increase in the transverse reinforcement ratio had no significant effect on the strength but influenced the failure mode. A non-linear finite element program based on the crack membrane model and using smeared-fixed crack approach was developed with a new aggregate interlock model incorporated into the finite element procedure. The finite element model was corroborated by experimental results of shear panels and walls. The finite element analysis of shear wall specimens indicated that while strengths can be predicted reasonably, the stiffness of edge elements has a significant effect on the deformational results for two-dimensional analyses. Therefore, to capture the deformation of walls accurately, three-dimensional finite element analyses are required. The shear wall design provisions given in the current Australian Standard and the Building Code of American Concrete Institute were compared with the experimental results. The comparison showed that the calculated strengths based on the codes are considerably conservative, specially when there exists the axial load.
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Meyer, Karl F. "Transfer and development length of 06-inch diameter prestressing strand in high strength lightweight concrete." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/20727.
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Islam, Md Shahidul. "Shear capacity and flexural ductility of reinforced high- and normal-strength concrete beams." Thesis, Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B1766536X.
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Reutlinger, Christopher George. "Direct pull-out capacity and transfer length of 06-inch diameter prestressing strand in high-performance concrete." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19026.
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Shams, Mohamed Khalil. "Time-dependent behavior of high-performance concrete." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/20682.
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Chau, Siu-lee, and 周小梨. "Effects of confinement and small axial load on flexural ductility of high-strength reinforced concrete beams." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B31997661.
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Wong, Hin-cheong Henry, and 黃憲昌. "Effects of water content, packing density and solid surface area on cement paste rheology." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39326032.
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Wong, Kong-yeung, and 黃剛揚. "Development of high strength concrete for Hong Kong and investigation of their mechanical properties." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B31213765.
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Lokuge, W. P. (Weena Priyanganie) 1967. "Stress-strain behaviour of confined high strength concrete under monotonically increasing and cyclic loadings." Monash University, Dept. of Civil Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/9425.
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Ghasemi, Sahar. "Innovative Modular High Performance Lightweight Decks for Accelerated Bridge Construction." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2248.
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At an average age of 42 years, 10% of the nation’s over 607,000 bridges are posted for load restrictions, with an additional 15% considered structurally deficient or functionally obsolete. While there are major concerns with decks in 75% of structurally deficient bridges, often weight and geometry of the deck further limit the load rating and functionality of the bridge. Traditional deck systems and construction methods usually lead to prolonged periods of traffic delays, limiting options for transportation agencies to replace or widen a bridge, especially in urban areas.
The purpose of this study was to develop a new generation of ultra-lightweight super shallow solid deck systems to replace open grid steel decks on movable bridges and as well serve as a viable alternative in bridge deck replacements across the country. The study has led to a lightweight low-profile asymmetric waffle deck made with advanced materials. The asymmetry comes from the arrangement of primary and secondary ribs, respectively perpendicular and parallel to the direction of traffic. The waffle deck is made with ultrahigh performance concrete (UHPC) reinforced with either high-strength steel (HSS) or carbon fiber reinforced polymer (CFRP) reinforcement. With this combination, the deck weight was limited to below 21 psf and its overall depth to only 4 inch, while still meeting the strength and ductility demands for 4 ft. typical stringer spacing. It was further envisioned that the ultra-high strength of UHPC is best matched with the high strength of HSS or CFRP reinforcement for an efficient system and the ductile behavior of UHPC can help mask the linear elastic response of CFRP reinforcement and result in an overall ductile system. The issues of consideration from the design and constructability perspectives have included strength and stiffness, bond and development length for the reinforcement, punching shear and panel action. A series of experiments were conducted to help address these issues. Additionally full-size panels were made for testing under heavy vehicle simulator (HVS) at the accelerated pavement testing (APT) facility in Gainesville. Detailed finite element analyses were also carried out to help guide the design of this new generation of bridge decks. The research has confirmed the superior performance of the new deck system and its feasibility.
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Halabi, Walid Charif. "High Strength concrete corbels." Thesis, University of Aberdeen, 1991. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU047734.
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Concrete is still the most widely used construction material of modern times. In very recent years attempts have been made by using steel fibre reinforcement to improve the inherent weaknesses that concrete possesses such as its low tensile strength and the tendency to shrink on drying and to creep under stress. In this context, the use of steel fibre reinforcement together with high strength concrete corbel joints has been investigated. This study came after fibre reinforced concrete had received wide recognition for its crack and deformation control, ductility and energy absorption characteristics. In the present study, the fracture behaviour and deformation characteristics of plain conventionally reinforced concrete corbels with and without steel fibre reinforcement has been investigated. The different types of steel fibres used and other experimental materials are described in chapter 3, whereas chapter 2 gives a review of the old and current design approaches used for concrete corbel design. In chapter 4 the deformation, cracking and ultimate strength of plain high strength concrete corbels has been studied with different cube strength ranged between 25 to 90 N/mm2. In chapter 5 a proposed theory to predict the ultimate strength of high and normal strength concrete corbels, conventionally reinforced, has been derived. The influence of steel fibre reinforcement on the performance of conventionally reinforced concrete corbels has been studied in chapter 6. Melt extract steel fibres were used in the majority of the corbels together with other types such as crimped, hooked and plastic fibres (polypropylene). In the same chapter 6, the theory has been extended to account for the strength gained by fibre addition. The effect of steel fibre reinforcement on the shear transfer strength has been studied in chapter 7. The theory proposed in chapter 5 has been further extended to predict the shear strength of 'push-off' type of specimens of plain and fibre reinforced concrete, with conventional steel reinforcement.
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Porras, Yadira A. "Durable high early strength concrete." Thesis, Kansas State University, 2018. http://hdl.handle.net/2097/38761.
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Master of ScienceDepartment of Civil Engineering
Mustaque A. Hossain
Based on a 2017 report on infrastructure by the American Society of Civil Engineers, 13% of Kansas public roads are in poor condition. Furthermore, reconstruction of a two-lane concrete pavement costs between $0.8 and $1.15 million dollars per lane mile. High early strength Portland cement concrete pavement (PCCP) patches are widely used in pavement preservation in Kansas due to the ability to open to traffic early. However, these repairs done by the Kansas Department of Transportation (KDOT) deteriorate faster than expected, though, prompting a need for inexpensive, durable high early strength concrete repair mixtures that meet KDOT standards (i.e., a 20-year service life). This study developed an experimental matrix consisting of six PCCP patching mixture designs with varying cement content and calcium chloride dosage. The mixtures were subjected to isothermal calorimetry, strength testing, drying shrinkage, and various durability tests. The effects of cement content and calcium chloride dosage on concrete strength and durability were then investigated. In addition, the compressive strength development with time, the split tensile versus compressive strength relationship, and the shrinkage strain of the PCCP patching mixtures were compared to established relationships provided by the American Concrete Institute (ACI). Results showed a maximum 3% increase in total heat generated by various concrete paste samples in isothermal calorimetry testing. The minimum compressive strength of 1,800 psi required by KDOT could likely be obtained using any of the PCCP mixtures, regardless of the cement content or calcium chloride dosage used in the study. Furthermore, surface resistivity tests for mixtures containing calcium chloride could result in erroneous measurements. Only one mixture satisfied the maximum expansion and minimum relative dynamic modulus of elasticity required by KDOT. Some ACI relationships for shrinkage and strength development do not appear to be valid for high early strength PCCP patching mixtures.
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El-Baden, Ali Said Ahmed. "Shrinkage of high strength concrete." Thesis, Cardiff University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531983.
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Li, Yang. "Blast Performance of Reiforced Concrete Beams Constructed with High-Strength Concrete and High-Strength Reinforcement." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35261.
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This thesis focuses on the dynamic and static behaviour of reinforced concrete beams built using high-strength concrete and high-strength steel reinforcement. As part of this study, a total of 8 high-strength concrete beams, built with and without steel fibres, and reinforced with high strength ASTM A1035 bars are tested under simulated blast loading using the University of Ottawa shock-tube, with an additional 3 companion beams tested under quasi-static loading. The variables considered in this study include: concrete type, fibre content, steel reinforcement ratio and steel reinforcement type. The behaviour of the beams with high-strength steel bars is compared to a companion set of beams reinforced with conventional steel reinforcement. The criteria used to evaluate the blast performance of the beams includes: overall blast capacity, maximum and residual displacements, secondary fragmentation and crack control. The dynamic results show that high strength concrete beams reinforced with high-strength steel are able to resist higher blast loads and reduce displacements when compared to companion beams with conventional steel reinforcement. The results also demonstrate that the addition of steel fibres is effective in controlling crack formation, minimizing secondary blast fragments, reducing displacements and further increasing overall blast capacity. However, the use of high-strength steel and high-strength concrete also shows potential for brittle failures under extreme blast pressures. The static results show that specimens with high-strength steel bars do not increase beam stiffness, but significantly increase peak load carrying capacity when compared to beams with the same ratio of conventional steel reinforcement. The analytical research program aims at predicting the response of the test beams using dynamic inelastic single-degree-of-freedom (SDOF) analysis and includes a sensitivity analysis examining the effect of various modelling parameters on the response predictions. Overall the analytical results demonstrate that SDOF analysis can be used to predict the blast response of beams built with high-strength concrete and steel reinforcement with acceptable accuracy.
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Lee, Kwang-Myong. "Interface fracture in high strength concrete." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12540.
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Mahawish, Ali Hassan. "Axisymmetric compression testing of concrete by nitrogen." Thesis, Cardiff University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316326.
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Branch, James. "Plastic properties of fresh high strength concrete." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/842953/.
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This thesis describes the novel test techniques that were developed to measure the parameters associated with the plastic shrinkage, and subsequent possible plastic shrinkage cracking, of high strength concrete. The parameters measured during the first 24 hours after placing were the stress- strain relationship, negative pore pressure and free shrinkage strain development. The plastic behaviour of eight high strength concrete mixes was quantified and these mixes were then tested to assess their propensity towards plastic shrinkage cracking, using restrained ring tests. A review of the parameters associated with plastic shrinkage cracking was carried out. The general view was that as the particle size in a cement matrix gets smaller, then the negative pore pressures developed are greater and hence shrinkage increases. This meant that the presence of secondary cementing materials, of very small diameter, such as microsilica, in high strength concretes would explain their apparent susceptibility to plastic shrinkage cracking. Eight high strength concrete mixes were tested in exposed and sealed conditions. It was found that when tested in sealed conditions none of the parameters measured presented itself as the sole driving force behind plastic shrinkage or plastic shrinkage cracking. Also, when cured in sealed conditions, none of the mixes tested in the restrained ring test apparatus cracked. When tested in exposed conditions, the presence of wind had little effect on the stress-strain relationship of the mixes tested. However the presence of wind seemed to cause negative pore pressures to develop earlier than in the sealed samples and increased free shrinkage by 3 to 40 times depending on the mix. The samples that exhibited the highest free shrinkage strains, in exposed conditions, were the mixes that cracked when tested in the restrained shrinkage rings. The mixes that cracked all contained microsilica and these mixes did not crack when the same mixes were tested without microsilica. Polypropylene fibres were found to reduce the cracked area of the samples that cracked. The supplementary cementing materials used in this study were ground granulated blast furnace slag, metakaolin, microsilica and pulverised fuel ash.
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Xue, Hongyu. "Structural behaviour of high strength concrete columns." Thesis, University of Westminster, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339246.
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Bush, Richard James. "Creep and shrinkage of high strength concrete." Thesis, Cardiff University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531922.
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Kong, Paul Y. L. "Shear strength of high performance concrete beams." Thesis, Curtin University, 1996. http://hdl.handle.net/20.500.11937/2600.
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An analytical and experimental investigation on the shear strength of High Performance Concrete (HPC) beams with vertical shear reinforcement or stirrups was carried out. The analytical work involved developing a theory based on the truss analogy, capable of predicting the response and shear strength of such beams subjected to combined bending moment and shear force.The experimental work comprised forty-eight beam specimens in eight series of tests. Most of the beams were 250 mm wide, 350 mm deep and had a clear span of approximately 2 metres. The largest beam was 250 mm wide, 600 mm deep and had a clear span of 3.1 metres. Test parameters included the concrete cover to the shear reinforcement cage, shear reinforcement ratio, longitudinal tensile steel ratio, overall beam depth, shear span-to-depth ratio and concrete compressive strength. The loading configurations included using one, two or four symmetrically placed concentrated loads on simply supported spans.The theory predicted the shear strength of the beams in the present study well. When beams from previous investigations were included, the theory also gave good prediction of the shear strength. Apart from this, comparisons of shear strength were also made with the predictions by the shear design provisions contained in the Australian Standard AS 3600 (1994), American Concrete Institute Building Code ACI 318-95, Eurocode EC2 Part 1 and Canadian Standard CSA A23.3-94. The AS 3600 method was found to give the best correlation with the test results among all the code methods.
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Kong, Paul Y. L. "Shear strength of high performance concrete beams." Curtin University of Technology, School of Civil Engineering, 1996. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=11337.
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An analytical and experimental investigation on the shear strength of High Performance Concrete (HPC) beams with vertical shear reinforcement or stirrups was carried out. The analytical work involved developing a theory based on the truss analogy, capable of predicting the response and shear strength of such beams subjected to combined bending moment and shear force.The experimental work comprised forty-eight beam specimens in eight series of tests. Most of the beams were 250 mm wide, 350 mm deep and had a clear span of approximately 2 metres. The largest beam was 250 mm wide, 600 mm deep and had a clear span of 3.1 metres. Test parameters included the concrete cover to the shear reinforcement cage, shear reinforcement ratio, longitudinal tensile steel ratio, overall beam depth, shear span-to-depth ratio and concrete compressive strength. The loading configurations included using one, two or four symmetrically placed concentrated loads on simply supported spans.The theory predicted the shear strength of the beams in the present study well. When beams from previous investigations were included, the theory also gave good prediction of the shear strength. Apart from this, comparisons of shear strength were also made with the predictions by the shear design provisions contained in the Australian Standard AS 3600 (1994), American Concrete Institute Building Code ACI 318-95, Eurocode EC2 Part 1 and Canadian Standard CSA A23.3-94. The AS 3600 method was found to give the best correlation with the test results among all the code methods.
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Edwards, Derek Oswald. "An investigation into possible means of increasing the strength of lightweight high strength concrete." Thesis, [Hong Kong] : University of Hong Kong, 1993. http://sunzi.lib.hku.hk/hkuto/record.jsp?B1331161X.
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Buchberg, Brandon S. "Investigation of mix design and properties of high-strength/high-performance lightweight concrete." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/23394.
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Wong, Kong-yeung. "Development of high strength concrete for Hong Kong and investigation of their mechanical properties /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19667711.
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Cladera, Bohigas Antoni. "Shear design of reinforced high-strength concrete beams." Doctoral thesis, Universitat Politècnica de Catalunya, 2003. http://hdl.handle.net/10803/6155.
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Aunque el hormigón de alta resistencia se está utilizando de manera creciente en los últimos años para la construcción de estructuras, la norma Española vigente, la Instrucción EHE, sólo abarca hormigones de resistencias características a compresión inferiores a 50 MPa. El aumento de resistencia del hormigón está directamente asociado a una mejora en la mayoría de sus prestaciones, especialmente de la durabilidad, aunque también produce un aumento en la fragilidad y una disminución de la rugosidad de las fisuras, lo que afecta de forma muy especial a la resistencia a cortante.El objetivo principal de este trabajo es contribuir al avance del conocimiento del comportamiento frente a la rotura por cortante de vigas de hormigón de alta resistencia. Para ello, y en primer lugar, se ha llevado a cabo una extensa revisión del estado actual del conocimiento de la resistencia a cortante, tanto para hormigón convencional como para hormigón de alta resistencia, así como una profunda investigación de campañas experimentales anteriores.
Se ha realizado una campaña experimental sobre vigas de hormigón de alta resistencia sometidas a flexión y cortante. La resistencia a compresión del hormigón de las vigas variaba entre 50 y 87 MPa. Las principales variables de diseño eran la cuantía de armadura longitudinal y transversal. Los resultados obtenidos experimentalmente han sido analizados para estudiar la influencia de las distintas variables en función de la resistencia a compresión del hormigón.
Con el objetivo de tener en cuenta, no sólo los resultados de nuestros ensayos, sino también la gran cantidad de información disponible en la bibliografía técnica, se ha preparado una base de datos con vigas de hormigón convencional y de alta resistencia a partir del banco de datos de la Universidad de Illinois. Los resultados empíricos han sido comparados con los cortantes últimos calculados según la Instrucción EHE, las especificaciones AASHTO LRFD, el Código ACI 318-99 y el programa Response-2000, basado en la teoría modificada del campo de compresiones.
Se han construido dos Redes Neuronales Artificiales (RNA) para predecir la resistencia a cortante en base a la gran cantidad de resultados experimentales. La principal característica de las RNA es su habilidad para aprender, mediante el ajuste de pesos internos, incluso cuando los datos de entrada y salida presentan un cierto nivel de ruido. Con los resultados de la RNA se ha realizado un análisis paramétrico de cada variable que afecta la resistencia última a cortante.
Se han propuesto nuevas expresiones que tienen el cuenta el comportamiento observado para el diseño frente al esfuerzo cortante de vigas tanto de hormigón convencional como de alta resistencia con y sin armadura a cortante, así como una nueva ecuación para la determinación de la armadura mínima a cortante. Las nuevas expresiones presentan resultados que se ajustan mejor a los resultados experimentales que los obtenidos mediante la utilización de las normativas vigentes.
Finalmente se han planteado varias sugerencias de futuras líneas de trabajo, que son resultado de la propia evolución del conocimiento sobre el tema de estudio durante el desarrollo de esta tesis.
Although High-Strength Concrete has been increasingly used in the construction industry during the last few years, current Spanish Structural Concrete code of practice (EHE) only covers concrete of strengths up to 50 MPa. An increase in the strength of concrete is directly associated with an improvement in most of its properties, in special the durability, but this also produces an increase in its brittleness and smoother crack surfaces which affects significantly the shear strength.
The aim of this research is to enhance the understanding of the behaviour of high-strength concrete beams with and without web reinforcement failing in shear. In order to achieve this objective, an extensive review of the state-of-the-art in shear strength for both normal-strength and high-strength concrete beams was made, as well as in-depth research into previous experimental campaigns.
An experimental programme involving the testing of eighteen high-strength beam specimens under a central point load was performed. The concrete compressive strength of the beams at the age of the tests ranged from 50 to 87 MPa. Primary design variables were the amount of shear and longitudinal reinforcement. The results obtained experimentally were analysed to study the influence of those parameters related to the concrete compressive strength.
With the aim of taking into account, in addition to the results of our tests, the large amount of information available, a large database was assembled based on the University of Illinois Sheardatabank for normal-strength and high-strength concrete beams. These test results were compared with failure shear strengths predicted by the EHE Code, the 2002 Final Draft of EuroCode 2, the AASHTO LRFD Specifications, the ACI Code 318-99, and Response-2000 program, a computer program based on the modified compression field theory.
Furthermore, two Artificial Neural Networks (ANN) were developed to predict the shear strength of reinforced beams based on the database beam specimens. An ANN is a computational tool made up of a number of simple, highly-interconnected processing elements that constitute a network. The main feature of an ANN is its ability to learn, by means of adjusting internal weights, even when the input and output data present a degree of noise. Based on the ANN results, a parametric study was carried out to study the influence of each parameter affecting the failure shear strength.
New expressions are proposed, taking into account the observed behaviour for the design of high-strength and normal-strength reinforced concrete beams with and without web reinforcement. A new equation is given for the amount of minimum reinforcement as well. The new expressions correlate with the empirical tests better than any current code of practice.
Finally, as a natural corollary to the evolution of our understanding of this field, some recommendations for future studies are made.
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Razvi, Salim R. "Confinement of normal and high-strength concrete columns." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/10075.
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A comprehensive research project was conducted to investigate the behaviour and design of earthquake resistant normal-strength and high-strength concrete columns. The project included three essential components; testing of full size columns, development of an analytical model, and development of a design procedure. The experimental program consisted of material research and structural testing. The first phase was designed to study mechanical properties of high-strength concrete, which involved testing of a large number of concrete cylinders. The second phase was designed to investigate performance of confined normal and high-strength concrete columns under concentric compression. The experimental program included tests of 46 full size square and circular columns, with concrete strength ranging between 60 MPa and 124 MPa. The parameters considered included; cross-sectional shape (circular and square), volumetric ratio and spacing of transverse reinforcement, distribution of longitudinal reinforcement and resulting tie arrangement, yield strength of transverse reinforcement, concrete compressive strength, influence of longitudinal reinforcement in circular columns, and type of circular reinforcement (continuous spiral and circular hoops). The analytical component of the research program involved development of a mathematical model to represent stress-strain relationship of confined concrete. This was done in two steps. The first step included formulation of the relationship for normal strength concrete, for which extensive test data was available. The second step involved modification of the model for high-strength concrete. An extensive literature survey was first conducted, followed by evaluation of previous test data. This information was used, along with the results of the experimental phase of this investigation to develop a generalized cofinement model for normal-strength and high-strength concrete columns. The analytical and experimental research was used in developing a design procedure for confinement of earthquake resistant concrete columns. The procedure includes all the relevant parameters of confinement that have been observed to be important in column tests, and relates the design variables to deformation capacities. A displacement based design methodology was developed, where the lateral drift demand is a design parameter. This approach leads to different confinement steel requirements for columns with different deformability demands, an approach currently lacking in practice. Furthermore, the reinforcement arrangement is recognized as a design parameter, allowing lower volumetric ratio of confinement reinforcement for efficient arrangements. This may result in significant savings in steel, eliminating the common problem of steel congestion in earthquake resistant columns. (Abstract shortened by UMI.)
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Logan, Andrew Thomas. "Short-Term Material Properties of High-Strength Concrete." NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-07252005-220433/.
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The need to extend the applicability of the AASHTO LRFD Bridge Design Specifications to high-strength concrete is being addressed by a series of projects being sponsored by the National Cooperative Highway Research Program (NCHRP). Among these projects, NCHRP Project 12-64 is being carried out at North Carolina State University (NCSU) to expand the use of the design specifications to 18,000 psi (124 MPa) for reinforced and prestressed concrete members in flexure and compression. As a part of this project, specimens were tested to determine the material properties of three high-strength concrete mixtures having target compressive strengths of 10,000, 14,000, and 18,000 psi (69, 97, and 124 MPa). The effects of various curing methods were also studied. This study covers the compressive strength, elastic modulus, Poisson?s ratio, and modulus of rupture of high-strength concrete. The study showed that extended curing beyond 7 days resulted in little or no increase in compressive strength. For predicting the elastic modulus of high-strength concrete, the ACI 318-02 or AASHTO-LRFD equation over-estimates the actual modulus while the ACI 363R-92 equation adequately predicts the measured value. The modulus of rupture equation in ACI 318-02 or AASHTO-LRFD gives a good approximation of the modulus of rupture of high-strength concrete when 1-day heat curing and 7-day moist curing are used. The equation from ACI 363R-92 gives a good estimate of modulus of rupture values for continually moist-cured specimens. The Poisson?s ratio of high-strength concrete is generally within the range of that reported for normal-strength concrete.
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Zhang, Lihe. "Impact resistance of high strength fiber reinforced concrete." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/705.
Full textAbstract:
Concrete structures may be subjected to dynamic loading during their service life. Understanding the dynamic properties of concrete structures is becoming critical because of the increased concern about the dynamic loading of both civilian and military structures, and especially, the recent increase in terrorist attacks on structures. Fiber reinforced concrete (FRC) is known to exhibit superior performance in its post-peak energy absorption capacity, (i.e., toughness) under flexural and tensile loading. However, the behavior of fiber reinforced concrete under compressive impact has not previously been investigated. In the present research, the response of fiber reinforced concrete was investigated over the full strain rate regime, from static loading to high strain rate loading, and finally to impact loading. The compressive toughness of FRC under static loading was studied using an existing Japanese standard (JSCE SF-5). Then, a test method for FRC under compressive impact loading was developed, involving the use of a high speed video camera system to measure the deformation of FRC cylinders under compressive impact.
The strain rate sensitivity of FRC in both flexure and compression was also fully investigated. FRC was found to have higher strengths under impact loading (both flexural and compressive) than under static loading. The compressive toughness under impact loading increased due to the high peak load and the high strain capacity. FRC under flexural impact loading showed a greater strength improvement than under static flexure. FRC displays a much higher Dynamic Improvement Factor (DIF) under flexural impact than under compressive impact. It gave an overall higher performance under impact than under static loading. It also exhibited a higher strain rate sensitivity than plain concrete in both compression and flexure.
Damage analysis, in terms of loss of strain energy, was carried out based on damage mechanics principles. Damage was found to increase with increasing strain rate. A new constitutive model was proposed to account for the relationship between DIF (Comp) and strain rate and the data derived from the model were found to be consistent with the experimental results.
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Denno, Mohamad Ghyath. "The durability of high strength lightweight aggregate concrete." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336389.
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Friis, Jesper. "Structural performance of confined high strength concrete columns." Thesis, City University London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397864.
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Moussalli, Tatiana 1978. "Performance issues for high strength concrete in bridges." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/84267.
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Reis, Jonathan M. "Structural Concrete Design with High-Strength Steel Reinforcement." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1277124990.
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Ezekiel, Samson. "Fire resistance simulation for high strength reinforced concrete." Thesis, London South Bank University, 2015. http://researchopen.lsbu.ac.uk/2084/.
Full textAbstract:
High strength reinforced concrete (HSRC) has been used more frequently in the construction of high rise buildings and other concrete structures in recent decades due to its advantages and excellent performance over normal strength and conventional reinforced concrete. Some of these advantages include: higher strength, better durability and allowance for provision of using less concrete and smaller section sizes. Although HSRC performs better than normal strength reinforced concrete (NSRC) at ambient temperatures, NSRC has been found to perform better than HSRC at elevated temperatures and fire conditions. Provision of adequate fire resistance for reinforced concrete (RC) structures is essential as fire represents an extreme loading and hazardous condition to which a structure might be exposed during its life span. The fire resistance of RC members is evaluated using a prescriptive approach which is irrational and conservative. Current codes of practice and construction in industry are moving towards performance based fire design method with computing software, which is a rationally based method with each structure designed to meets its own need. This method requires comprehensive knowledge and modelling of concrete and reinforcement material behaviour and their response at elevated temperatures. The fire resistance of HSRC members (columns and beams) in this study was evaluated using a three-dimensional Finite Element (FE) model created in ANSYS. The stress – strain behaviour of concrete proposed in this research was used in modelling the behaviour of concrete in ANSYS, while other concrete and steel material properties were accounted for by using models proposed by other researchers. The fire resistance of the HSRC members is evaluated using coupled field analysis (thermal – structural analysis) with performance based failure criteria provided in the code of practice. The accuracy of the FE model was verified by comparing the thermal response, structural response and predicted fire resistance with fire test results obtained. Using the validated FE model, parametric studies were conducted to investigate the influence of various parameters affecting the fire performance of HSRC members exposed to fire. From the parametric studies conducted, simplified calculation models were developed for evaluating the resistance of HSRC members (columns and beams) exposed to fire. These models were validated with results from ANSYS and a fire resistance test. The simple model accounts for major factors such as member size, load ratio and fire scenario, and therefore can be easily incorporated into structural design. The FE model and simple calculation model provide a rational approach for evaluating the fire resistance of HSRC (members) and predict a more accurate fire resistance than the prescriptive approach.
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Ahmed, El-Mahadi. "Rheological properties, loss of workability and strength development of high-strength concrete." Thesis, University College London (University of London), 2002. http://discovery.ucl.ac.uk/1317867/.
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The successful production of high-strength concrete which meets the desired strength and durability is dependent on optimising its rheological (or flow) properties and reducing its loss of workability during the transportation, placing and compaction stages. The research presented in this thesis aimed to: 1. Determine whether mix stability and compactability can be adequately described by the two Bingham parameters of yield value and plastic viscosity. 2. Reduce the uncertainties in material selection with regards to the performance of superplasticizers and cement replacement materials. 3. Examine how the two Bingham parameters vary at different degrees of compaction by vibration. 4. Determine how these influence the strength development characteristics in the hardened state. 5. An additional aim was to carry out any modifications to the test apparatus and methods which experience makes necessary. Measurements with Tattersall's MH two-point workability test apparatus indicated that mix stability correlates more closely with the yield value than with plastic viscosity, whilst the opposite is true with respect to compactability under self-weight. The performance of conventional and new-generation superplasticizers (based on SMF, SNF, MLS, Vinyl and Acrylate polymers) was evaluated with different dosages, mixing procedures and cements. The SNF superplasticizer produced slightly lower initial workabilities than the Acrylate superplasticizer, but the longest workability retentions of the superplasticizers tested. Partial cement replacements by CSF in binary blends produced lower superplasticizer dosage demands, higher initial workabilities and longer workability retentions than those due to PFA and GGBS. When used in ternary blended cements, CSF enhanced the performance of mixes containing PFA or GGBS at w/b ratios of 0.30-0.22. A novel method developed to assess the vibration response of fresh concretes has, for the first time, demonstrated that both the yield value and plastic viscosity decrease during compaction. The method has also demonstrated that the maximum compressive strengths and densities of concretes compacted for different vibration durations/amplitudes coincide with the attainment of zero yield value. Continuous reductions in plastic viscosity during vibration mainly reduced the homogeneity of concrete compacted in short columns.
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Soutsos, Marios Nicou. "Mix design, workability heat evolution and strength development of high strength concrete." Thesis, University College London (University of London), 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308062.
Full textAbstract:
A literature survey of the properties and uses of high strength concrete, defined for this study as having a strength in excess of 60 N/tnm2, has shown that of prime need is a systematic, reproducible procedure for attaining high strength concrete. The "Maximum Density Theory", i.e. the requirement that the aggregate occupies as large a relative volume as possible, has been adopted as an approach to optimisation of the mix proportions. However, this does not consider the effect that the aggregate suIface area has on the requirement of excess paste for lubrication. To investigate the combined effect of void content and surface area, mixes with lower sand proportions than that required for minimum void content were tested for slump. The optimum sand proportion is the one that produces the highest slump, for a particular cement content. This procedure has been called: "The Modified Maximum Density Theory". Having thus optimised the cement and aggregate contents, partial cement replacement by mineral admixtures, at low water-cement ratios, has been investigated in order to assess: a) their contribution to long term strengths, b) their contribution to reducing the heat evolution of concrete mixes, and c) their effect on the workability of concrete. Condensed silica fume (at replacement levels of up to 15%) produced higher compressive strengths than ordinary Portland cement. Ground granulated blast furnace slag (at replacement levels of up to 30%) can be used without decreasing the 28-day strength. Replacement by 20% pulverised fuel ash resulted in a 15% decrease in the 28-day strength and equal strength to ordinary Portland cement concrete at ages beyond 56-days. Temperature measurements during hydration, under adiabatic conditions, have however shown that these replacement levels do not lower the temperature rise at a water-binder ratio of 0.26. The higher levels required for significant temperature reduction will also cause a significant reduction in the strength. To offset this ground granulated blast furnace slag (58%) and pulverised fuel ash (36%) in combination with 10% condensed silica fume 4 were used. These combinations reduced the temperature rise by more than 10°C while the reduction in the 28-day compressive strength was less than 15%. Partial cement replacement by pulverised fuel ash and ground granulated blast furnace slag improved the workability and therefore allowed a reduction in the superplasticiser dosage required for a given slump. The use of condensed silica fume reduces the workability at low superplasticiser dosages, but it has a water-reducing effect above a certain superplasticiser dosage. Results from these studies have been used to formulate guidelines for the proportioning of materials for producing high strength concrete.
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Marquis, Glenn M. "Effect of high-strength concrete on the seismic response of concrete frames." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ37270.pdf.
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Soleymani, Ashtiani Mohammad. "Seismic performance of high-strength self-compacting concrete in reinforced concrete structures." Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2013. http://hdl.handle.net/10092/9162.
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Self-compacting concrete (SCC) was first developed in Japan about two decades ago. Since then, it has been offered as a solution to various challenges inherently associated with traditional concrete construction; i.e. quality and speed of construction, impact of unskilled labour force and noise pollution etc. SCC flows into a uniform level under its own weight and fills in all recesses and corners of the formwork even in highly congested reinforcement areas. In recent years the interest in using SCC in structural members has increased manifold; therefore many researchers have started investigating its characteristics. Nevertheless, before this special concrete is widely accepted and globally used in structures, its structural performance under different conditions should be investigated.
This research focuses on investigating the behaviour of high strength self-compacting concrete (HSSCC) in reinforced concrete (RC) structures through a systematic approach in order to bridge part of an existing gap in the available literature. The dissertation is comprised of four main stages; namely, mix design development and mechanical properties of HSSCC, bond performance of deformed bars in HSSCC, experimental investigation on interior RC beam-column joints (BCJs) cast with HSSCC under reversed cyclic excitations, and finally finite element (FE) modelling and analysis of interior BCJs.
First, a HSSCC mix proportion yielding compressive strength greater than 100 MPa was developed in the laboratory using locally available materials in New Zealand. Two benchmark concrete mixes of conventionally-vibrated high-strength concrete (CVHSC) and normal-strength conventionally vibrated concrete (CVC) were also designed for comparison purposes. Material characteristics (such as compressive, splitting tensile and flexural strengths as well as modulus of elasticity, shrinkage and microstructural properties) of all mixes were evaluated. It was found that, once the lower quality of material in normal strength concrete is offset by achieving a denser mix in high-strength concrete, mechanical properties of HSSCC are equivalent to or higher than those in CVHSC.
Given that the performance of RC structures (and in specific BCJs) is highly dependent on bond between reinforcement and concrete, understanding the bond behaviour in HSSCC was an imperative link between the first and third phases of this research. Therefore, the second phase focused on scrutinizing bond properties of deformed bars in HSSCC using monotonic pull-out and innovative cyclic beam tests. Processing of the pull-out results revealed that a shorter development length may be utilized in HSSCC. In addition, the grade (or ductility) of reinforcing steel was found to substantially influence the post-yield bond performance. Important modifications to the bond model used in the CEB-FIP model code and Maekawa’s bond-slip-strain relationship were suggested from the results of this phase. An innovative cyclic beam specimen and test setup were also designed such that a more realistic bond performance could be observed in the laboratory tests compared to that in real RC structures. Deleterious impact of cyclic loading and buckling of reinforcement on bond performance were investigated using this testing protocol.
The third phase of this research focused on the design, fabrication and testing of seven full-size BCJs. BCJs are one of the most critical parts in RC frame structures and their response substantially affects the overall behaviour of the structure. In seismically active regions like New Zealand, the criticality of BCJs is exacerbated with the complexities involved in seismic resistance. The already congested intersection of RC beam and column looks more like a solid steel connection after consideration of earthquake requirements, and placement of concrete becomes problematic in such areas. At the same time, in many of the high-rise structures, normal strength concrete does not meet the capacity requirements; this requires the usage of high-strength concrete. Therefore, once the seismic performance of HSSCC is guaranteed, it can possibly be a solution to both the capacity and compaction problems. Variables such as axial load, concrete type, steel grade, casting direction, and joint shear reinforcement were considered variable in the experimental investigations. It was found that HSSCC has similar seismic performance to that of CVHSC and it can also be incorporated in the joint area of CVC for an enhanced performance.
Finally, DIANA (a nonlinear FE program) was used to simulate the experimental results obtained in the third phase of this research. All BCJs were successfully modelled using their relevant attributes (such as the mechanical properties of HSSCC, steel stress-strain response, test setup and loading protocol) and nonlinear FE analyses (FEA) were performed on each model. FE results were compared to those obtained in the laboratory which showed a reasonable agreement between the two. The capabilities of the FEA were scrutinized with respect to the hysteresis loops, energy dissipation, joint shear deformations, stress development in the concrete and steel, and drift components.
Integrating the results of all stages of this research provided better understanding of the performance of HSSCC both at the material and structural levels. Not only were none of the seismically important features compromised by using HSSCC in BCJs, but also many other associated benefits were added to their performance. Therefore, HSSCC can be confidently implemented in design of RC structures even in seismically active regions of the world.
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Roenker, Andrew T. "Testing of Torque-and-Angle High Strength Fasteners." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1490701582262578.
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Dunbeck, Jennifer. "Evaluation of high strength lightweight concrete precast, prestressed bridge girders." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28091.
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HUANG, PO-CHIA, and 黃柏嘉. "Seismic Testing of High-Strength Reinforced Concrete Exterior Beam-Column-slab connections." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/49818516948465088936.
Full textAbstract:
碩士國立雲林科技大學
營建工程系
104
To study the degradation of joint shear strength, this paper designed four New RC exterior beam-column connections with slabs and transverse beams covers 2/3 or 3/4 width of the joint face using current codes. Four beam-column connections were made with 70 MPa concrete, SD685 longitudinal reinforcement and SD785 transverse reinforcement. Test results showed that the current ACI 318 code is conservative. The transverse beams which covered 2/3 width of the joint face still had some confining effect to enhance the joint shear strength. Typical pushover analysis use beam-column centerline models with rigid joints, which may get unconservative results. This paper also presents nonlinear modeling of the joint with two equivalent compression struts using a commercial structural analysis tool. Following the recommendations of ASCE 41 and ACI 369, the joint keep elastic if the shear demand is less than the nominal shear strength. This paper propose to model the joint shear failure after beam yielding. Using empirical formula obtained by prior database investigation, the joint nonlinear springs are adjusted according to the prediction of failure mode. The proposed skills can improve the results of pushover analysis and well predict the envelopes for the cyclic loading test results. Further calibration and verification of the modeling parameters are recommended to widely use in practice.
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Liu, Wen-hao, and 柳文皓. "Seismic Testing of High-Strength Reinforced Concrete Interior Beam-Colunm-slab connections." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/z9fj97.
Full textAbstract:
碩士國立雲林科技大學
營建工程系
104
For high-rise buildings, columns made of normal-strength reinforced concrete have large cross-sectional dimensions which cannot be accepted by end users. Using high-strength reinforcement and concrete have many advantages, including smaller member sizes, lighter structure elements, lesser steel reinforcement, longer span capability, and more space available for end users. This paper presents experiments of the sub-project “behavior, design, and modeling of new RC frame joints subjected to seismic loading” in the Taiwan New RC Project. Four new RC interior beam-column connections with transverse beams and slabs were tested according to the acceptance criteria for moment frames, evaluating the effect of transverse beams covers 1/2 or 3/4 width of the joint face. The degradation of the joint shear strength is also investigated. Four beam-column connection specimens were made with 100-MPa concrete, SD685 longitudinal reinforcement, and SD785 transverse reinforcement. Two connection specimens have precast concrete units with cast-in-place concrete joint and slabs, while the other two specimens are monolithic beam-column-slab connections. Test results show that the precast beams and columns with cast-in-place concrete joint perform as well as expected for seismic design of moment frames. Test results shows that the 1/2-column-width-wide transverse beams still have partial confinement effect. It is recommended that the nominal joint strength between calculated by linear interpolation between 1.25√(f_c^' ) MPa(15√(f_c^' ) psi) and 1.67√(f_c^' ) MPa(20√(f_c^' ) psi) for transverse beams cover 1/2 and 3/4 width of the column, respectively.
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Wu, Y. F. (Yu-Fei). "Seismic retrofitting of rectangular reinforced concrete columns with partial interaction plating." 2002. http://web4.library.adelaide.edu.au/theses/09PH/09phw9591.pdf.
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Wu, Y. F. (Yu-Fei). "Seismic retrofitting of rectangular reinforced concrete columns with partial interaction plating / by Yu-Fei Wu." Thesis, 2002. http://hdl.handle.net/2440/21836.
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"June 2002"Includes bibliographical references (leaves 349-374)
xxxix, 416 leaves : ill., plates ; 30 cm.
Thesis (Ph.D.)--University of Adelaide, Dept. of Civil and Environmental Engineering, 2002
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Clark, W. S. "Axial load capacity of circular steel tube columns filled with high strength concrete." Thesis, 1994. https://vuir.vu.edu.au/18153/.
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This study examines the axial load capacity of circular Concrete Filled Steel Tube
columns using High Strength Concrete (CFST-HSC). Emphasis is drawn to the
enhanced axial capacity of short columns attributed to the lateral confinement of the
concrete infill provided by the steel encasement. The degree of confinement has been
found to be dependent on several geometric and mechanical parameters. At present,
significant discrepancies exist with respect to quantifying the effective strength confined concrete. Existing design models and codes are predominantly derived from
the characteristics of normal strength concrete and therefore may be inappropriate concrete filled steel columns utilising High Strength Concrete (HSC).
An extensive experimental program was initiated to examine the axial capacity of
CFST-HSC columns. The results of 62 concentrically loaded scale model columns filled
with High Strength Concrete (46-100 MPa) are presented. The principal experimental
parameters were concrete and steel strengths, tube diameter to wall thickness ratio, column slenderness ratio. The columns tested were classified as short thin walled
sections and were tested as isolated column elements under short term loading. The
results are compared with the predictions of several existing design procedures and
recommendations are proposed.
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Kuan-Yu, Wu, and 吳光育. "Torsional Strength of Plain High-Strength Concrete Beams." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/58241856552406229060.
Full textAbstract:
碩士國立臺灣科技大學
營建工程技術學系
83
The ultimate torsional strengths of plain concrete beams are currently calculated by the elastic theory, the plastic theory and the skew-bending theory. However, these theories are entirely based on tests of low-strength concrete beams. Therefore, it is necessary to examine the applicability of these theories when applied to plain high-strength concrete beams subject to pure torsion. In this study, twenty specimens were tested under pure torsion to investigate the effects on torsional strength of concrete strength ,specimen shape and specimen size. Tests results indicate that for high-strength concrete beams, the ultimate torsional strengths calculated using the elastic theory are quite reasonable for T- and L- beams , but overly conservative for rectangular beams. The plastic theory can reasonably predict the torsional strengths of smaller concrete beams. For larger beams , however , the plastic theory overestimates their torsional strengths. The torsional strengths predicted using the skew-bending theory in terms of concrete strength are quite reasonable for beams of T- and L- sections , but slightly conservative for smaller rectangular beams.
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Zaina, M. "Strength and ductility of fibre reinforced high strength concrete columns /." 2005. http://www.library.unsw.edu.au/~thesis/adt-NUN/public/adt-NUN20051114.101729/index.html.
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Huang, Ming-Ke, and 黃茗科. "Rebound Number Testing for Strength of Hardened Concrete." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/77343228105784612143.
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