Shear Capacity and Flexural Ductility of Reinforced High- and Normal-strength Concrete Beams PDF Download

Author: Md. Shahidul Islam
Publisher:
ISBN:
Category : Concrete beams
Languages : en
Pages : 100

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Author: Md Shahidul Islam
Publisher: Open Dissertation Press
ISBN: 9781374753815
Category :
Languages : en
Pages :

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This dissertation, "Shear Capacity and Flexural Ductility of Reinforced High- and Normal-strength Concrete Beams" by Md Shahidul, Islam, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. DOI: 10.5353/th_b3121444 Subjects: Concrete beams - Testing High strength concrete - Testing Shear (Mechanics)

Author: Siu-Lee Chau
Publisher:
ISBN: 9781361234099
Category :
Languages : en
Pages :

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This dissertation, "Effects of Confinement and Small Axial Load on Flexural Ductility of High-strength Reinforced Concrete Beams" by Siu-lee, Chau, 周小梨, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled EFFECTS OF CONFINEMENT AND SMALL AXIAL LOAD ON FLEXURAL DUCTILITY OF HIGH-STRENGTH REINFORCED CONCRETE BEAMS Submitted by CHAU Siu Lee for the Degree of Master of Philosophy at The University of Hong Kong in August 2005 Compared with normal-strength concrete, high-strength concrete has higher strength but is generally more brittle. Its use in a reinforced concrete structure could lead to an undesirable reduction in ductility if not properly controlled. In this thesis, the effects of confinement and small axial load on the flexural ductility of reinforced concrete beams cast of both normal- and high-strength concrete have been evaluated by analyzing the complete moment-curvature behaviour of the beam sections. The results reveal that the use of high-strength concrete would at a constant tension steel ratio increase the flexural ductility, while at a constant tension to balanced steel ratio decrease the ductility. On the other hand, provision of confinement enhances the ductility of both normal- and high-strength concrete sections at both a constant tension steel ratio and at a constant tension to balanced steel ratio. It does this in two ways. Firstly, it increases the balanced steel ratio of the section. So, for a constant steel ratio, the section with higher confinement is more under-reinforced. Secondly, it increases the residual strength and ductility of the concrete such that at the same tension to balanced steel ratio, the ductility of the section increases. From the results of the analysis, it can be concluded that providing confinement to a section is an effective way of improving the ductility of reinforced concrete beam sections, especially those cast of high-strength concrete. However, most codes of practice do not specify a suitable design method for reinforced concrete beams that takes into account the effect of confinement. Therefore, design formulas for the flexural strength and ductility design of high-strength concrete beams with the effects of confinement taken into account have been developed. On the other hand, it is proposed to compensate for the reduction in flexural ductility due to the use of high-strength concrete by adding compression and/or confining reinforcement. A simple design method that correlates the amount of addition reinforcement needed to maintain a constant level of minimum ductility and the concrete strength is developed. Conversely, the presence of compressive axial load, even at a low level, has an adverse effect on flexural ductility. As a portion of concrete is used to resist the axial load, the section becomes less under-reinforced. Therefore, the flexural ductility decreases with the level of axial load applied. From the results obtained, it is found that the presence of axial load mainly affects the degree of the section being under- or over-reinforced. Measures should therefore be taken to maintain the ductility level of sections with applied axial load at an acceptable level. The study recommends the provisions of additional compression reinforcement to resist the applied axial load, and proposes a design method for restoring the ductility of a section with applied axial load to a ductility level attained by an identical section without axial load. DOI: 10.5353/th_b3199766 Subjects:

Author: James Grierson MacGregor
Publisher: Prentice Hall
ISBN: 9780136139850
Category : Reinforced concrete
Languages : en
Pages : 939

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Based on the 1995 edition of the American Concrete Institute Building Code, this text explains the theory and practice of reinforced concrete design in a systematic and clear fashion, with an abundance of step-by-step worked examples, illustrations, and photographs. The focus is on preparing students to make the many judgment decisions required in reinforced concrete design, and reflects the author's experience as both a teacher of reinforced concrete design and as a member of various code committees. This edition provides new, revised and expanded coverage of the following topics: core testing and durability; shrinkage and creep; bases the maximum steel ratio and the value of the factor on Appendix B of ACI318-95; composite concrete beams; strut-and-tie models; dapped ends and T-beam flanges. It also expands the discussion of STMs and adds new examples in SI units.

Author: Ching-Ming Johnny Ho
Publisher: Open Dissertation Press
ISBN: 9781374713376
Category : Technology & Engineering
Languages : en
Pages : 328

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This dissertation, "Inelastic Design of Reinforced Concrete Beams and Limited Ductile High-strength Concrete Columns" by Ching-ming, Johnny, Ho, 何正銘, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled INELASTIC DESIGN OF REINFORCED CONCRETE BEAMS AND LIMITED DUCTILE HIGH-STRENGTH CONCRETE COLUMNS submitted by Ho Ching Ming Johnny for the degree of Doctor of Philosophy at The University of Hong Kong in January 2003 This thesis studies the inelastic analysis and design of normal- and high-strength reinforced concrete beams and high-strength reinforced concrete columns. Particular attention is given to the proposed design method of limited ductile high-strength reinforced concrete columns. Analytical studies on normal- and high-strength reinforced concrete beams and experimental research on high-strength reinforced concrete columns are conducted and discussed. To investigate the post-peak behaviour and flexural ductility performance of reinforced concrete beams and columns, the author proposes a new method of rigorous nonlinear moment-curvature analysis that incorporates the strain history effect of tension steel. The moment-curvature curves derived using the new method resemble more closely the actual post-peak behaviour of reinforced concrete members compared to their conventionally-derived counterparts. The results enable the author to derive: (1) a theoretical equation that correlates the curvature ductility factor of reinforced concrete beams to various structural parameters; (2) two sets of design ultimate concrete strains suitable for use with either the proposed equivalent rectangular concrete stress block or the equivalent rectangular stress block of BS 8110; and (3) a series of design charts that facilitates the concurrent design of flexural strength and ductility of reinforced concrete beams. A new parametric study using the proposed analysis method is also conducted to refine the author's previously-proposed equation on transverse steel content of limited ductile high-strength reinforced concrete columns. A series of high-strength reinforced concrete columns containing transverse reinforcement calculated in accordance with this refined equation are tested under compressive axial load and reversed cyclic inelastic displacements to assess its adequacy. These columns prove capable of achieving a curvature ductility factor close to 10, which is the commonly-accepted measure for limited ductile structures. They are subsequently compared with another series of columns containing transverse steel calculated in accordance with the shear requirement of BS 8110. The performance of the latter series is shown to be much worse than the former in terms of flexural strength and ductility. The influence of transverse steel configuration is investigated on some test specimens selected from these two series of columns. In addition, three column specimens are tested to investigate the effect of tension steel lap splice. The test results indicate that the lap splice should be located further away from the potential plastic hinge region. The author also proposes a rational evaluation of plastic hinge length, which could hitherto only be assessed empirically during experimental tests, using various methods that can be grouped into direct and indirect methods. The results are compared with the experimental data obtained from the majority of the column test specimens and with the experimental data obtained by other researchers, and they match closely. To facilitate the design of limited ductile hig

Author: Roya Solhmirzaei
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 287

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Ultra high performance concrete (UHPC) is an advanced cementitious material made with low water to binder ratio and high fineness admixtures, and possesses a unique combination of superior strength, durability, corrosion resistance, and impact resistance. However, increased strength of UHPC results in a brittle behavior. To overcome this brittle behavior of UHPC and improve post cracking response of UHPC, steel fibers are often added to UHPC and this concrete type is designated as Ultra High Performance Fiber Reinforced Concrete (UHPFRC). Being a relatively new construction material, there are limited guidelines and specifications in standards and codes for the design of structural members fabricated using UHPFRC. To develop a deeper understanding on the behavior of UHPFRC flexural members, seven beams made of UHPFRC are tested under different loading conditions. The test variables include level of longitudinal reinforcement, type of loading (shear and flexure), and presence of shear reinforcement. Further, a finite element based numerical model for tracing structural behavior of UHPFRC beams is developed in ABAQUS. The developed model can account for the nonlinear material response of UHPFRC and steel reinforcement in both tension and compression, as well as bond between concrete and reinforcing steel, and can trace the detailed response of the beams in the entire range of loading. This model is validated by comparing predicted response parameters including load-deflection, load-strain, and crack propagation against experimental data obtained from tests on UHPFRC beams with different material characteristics and under different loading configurations. The validated model is applied to conduct a set of parametric studies to quantify the effect of different parameters on structural response of UHPFRC beams, including the contribution of stirrups and concrete to shear capacity of beams, to explore feasibility of removing the need for shear reinforcement in UHPFRC beams. Results from experiments and numerical model reveal that UHPFRC beams exhibit distinct cracking pattern characterized by the propagation of multiple micro cracks followed by widening of a single crack leading to failure. Also, UHPFRC beams exhibit high flexural and shear capacity, as well as ductility due to high compressive and tensile strength of UHPFRC and fiber bridging developing at the crack surfaces that leads to strain hardening in UHPFRC after cracking. Thus, absence of shear reinforcement in UHPFRC beams does not result in brittle failure, even under dominant shear loading. Data from the conducted experiments as well as those reported in literature is utilized to develop a machine learning (ML) framework for predicting structural response of UHPFRC beams. On this basis, a comprehensive database on reported tests on UHPFRC beams with different geometric, fiber properties, loading and material characteristics is collected. This database is then analyzed utilizing different ML algorithms, including support vector machine, artificial neural networks, k-nearest neighbor, support vector machine regression, and genetic programing, to develop a data-driven computational framework for predicting failure mode and flexural and shear capacity of UHPFRC beams. Predictions obtained from the proposed framework are compared against the values obtained from design equations in codes, and also results from full-scale tests to demonstrate the reliability of the proposed approach. The results clearly indicate that the proposed ML framework can effectively predict failure mode and flexural and shear capacity of UHPFRC beams with varying reinforcement detailing and configurations. The research presented in this dissertation contributes to the development of preliminary guidance on evaluating capacity of UHPFRC beams under different configurations.

Author: H. G. Russell
Publisher:
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 296

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Author: Shuenn-Yih Chang
Publisher: CRC Press
ISBN: 0203388070
Category : Technology & Engineering
Languages : en
Pages : 974

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Advances in Civil Engineering and Building Materials presents the state-of-the-art development in: - Structural Engineering - Road & Bridge Engineering- Geotechnical Engineering- Architecture & Urban Planning- Transportation Engineering- Hydraulic Engineering - Engineering Management- Computational Mechanics- Construction Technology- Buildi

Author: Roukaya Bastami
Publisher:
ISBN:
Category :
Languages : en
Pages :

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This thesis presents the results of a research program examining the effects of macro-synthetic fibers on the shear and flexural behaviour of high-strength concrete (HSC) beams subjected to static and blast loads. As part of the study, a series of seventeen fiber-reinforced HSC beams are built and tested under either quasi-static four-point bending or simulated blast loads using a shock-tube. The investigated test parameters include the effects of: macro-synthetic fibers, fiber hybridization, combined use of fibers and stirrups and longitudinal steel ratio and type. The results show that under slowly applied loads, the provision of synthetic fibers improves the shear capacity of the beams by allowing for the development of yield stresses in the longitudinal reinforcement, while the combined use of synthetic fibers and stirrups is found to improve flexural ductility and cracking behaviour. The results also show that the provision of synthetic fibers delays shear failure in beams tested under blast pressures, with improved control of blast-induced displacements and increased damage tolerance in beams designed with combined fibers and stirrups. The study also shows that the use of hybrid fibers was capable of effectively replacing transverse reinforcement under both loading types, allowing for ductile flexural failure. Moreover, the use of synthetic fibers was effective in better controlling crushing and spalling in beams designed with Grade 690 MPa high-strength reinforcement. Furthermore, the results demonstrate that synthetic fibers can possibly be used to relax the stringent detailing required by modern blast codes by increasing the transverse reinforcement hoop spacing without compromising performance. As part of the analytical study, the load-deflection responses (resistance functions) of the beams are predicted using sectional (moment-curvature) analysis, as well as more advanced 2D finite element modelling. Dynamic resistance functions developed using both approaches, and incorporating material strain-rate effects, are then used to conduct non-linear single-degree-of-freedom (SDOF) analyses of the blast-tested beams. In general, the results show that both methods resulted in reasonably accurate predictions of the static and dynamic experimental results.

Author: W. B. Cranston
Publisher:
ISBN:
Category : Columns, Concrete
Languages : en
Pages : 18

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