Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains viii, 114 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 112-114).

Thesis (M.S. in in civil engineering)--Washington State University, December 2009. / Title from PDF title page (viewed on Jan. 26, 2010). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 42).

Thesis (M.S.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 179-180). Also available via World Wide Web.

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 66-68). Also available in print.

Akademisk avhandling - Chalmers tekniska hogskola, Gothenburg, Sweden. / "Doktorsavhandlingar vid Chalmers tekniska hogskola." Bibliography: p. [441]-444.

Thesis--M. Phil., University of Hong Kong.

Thesis (Ph. D.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xii, 160 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 104-106).

The stress-strain characteristics of concrete developed in flexure is very important for flexural strength design of reinforced concrete (RC) members. In current RC design codes, the stress-strain curve of concrete developed in flexure is obtained by scaling down the uni-axial stress-strain curve to account for the strain gradient effect. Therefore, the maximum concrete stress that can be developed under flexure is smaller than its uni-axial strength, and the use of which always underestimates the flexural strength of RC beams and columns even though the safety factors for materials are taken as unity. Furthermore, the value of strength underestimation was different for RC beams and columns, which indicates that the extent of strain gradient will affect the maximum concrete stress and stress-strain curve developed under flexure. To investigate the maximum concrete stress, 29 column specimens were fabricated and tested in this study. They were divided into 9 groups, each of which was poured from the same batch of concrete and contained specimens with identical cross-section properties. In each group, one specimen was tested under concentric load while the rest was/were subjected to eccentric or horizontal load. To study the strain gradient effects, the ratio of the maximum concrete compressive stress developed in the eccentrically/horizontally loaded specimens to the maximum uni-axial compressive stress developed in the counterpart concentrically loaded specimens, denoted by k3, is determined based on axial force and moment equilibriums. Subsequently, the concrete stress block parameters and the equivalent rectangular concrete stress block parameters are determined. It is found that the ratios of the maximum and equivalent concrete stress to uni-axial cylinder strength, denoted respectively by k3 and , depend significantly on strain gradient, while that of the depth of stress block to neutral axis depth, denoted by , remains relatively constant with strain gradient. Design equations are proposed to relate and  with strain gradient for strength calculation, whose applicability is verified by comparing the strengths of RC beams and columns tested by various researchers with their theoretical strengths predicted by the proposed parameters and those evaluated based on provisions of RC codes. Based on the test results, the stress-strain curve of normal-strength concrete (NSC) developed under strain gradient is derived using least-square method by minimising the errors between the theoretical axial load and moment and the respective measured values. Two formulas are developed to derive the flexural stress-strain curve, whose applicability is verified by comparing the predicted strength with those measured by other researchers. Lastly, the application of the proposed stress-block parameters and stress-strain curve of NSC will be illustrated by developing some charts for flexural strength design of NSC beams and columns. The application will further be extended to develop strength-ductility charts for NSC beams and columns, which enable simultaneous design of strength and ductility. By adopting the proposed design charts, the flexural strength design, as well as that of the plastic hinge forming mechanism during extreme events, will be more accurate. The resulting design will be safer, more environmentally friendly and cost effective. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

Existing reinforced concrete (RC) structure can be strengthened upon the addition of externally bonded high-strength light-weight fibre-reinforced polymer (FRP) composites. An abundance of research over the last two decades has established the effectiveness of the externally bonded FRP via extensive experimental testing. Perhaps the most commonly occurring failure mode though is premature debonding of the FRP and debonding generally occurs at strains well below the strain capacity of the FRP. Debonding failures are undesirable as they are typically brittle and represent an under-utilisation of the FRP material. A straightforward means to prevent or at least delay debonding is by the addition of mechanical anchors, however, research to date on anchors is extremely limited. Of the various anchor concepts examined to date by researchers, this dissertation will focus on anchors made from FRP which are herein referred to as FRP anchors. The details and results of a program of research on the performance of FRP anchors in FRP-strengthened structures are presented in this dissertation. An extensive review of exiting literature helps establish knowledge gaps which serve to justify the need and the scope of the research reported herein. A novel bow-tie FRP anchor concept is then proposed and tested in smaller-scale single-shear FRP-to-concrete joint assemblages as well as larger-scale simply-supported FRP-strengthened RC slabs. The anchors are shown to increase the strength and slip capacity of the joints by up to 41 % and almost 600 %, respectively, in comparison with unanchored control joints. The anchors are then shown to increase the load and deflection capacity of slabs by 30 % and 110 %, respectively, above an unanchored control slab. In addition to strength, it is the ability of FRP anchors to introduce deformability into FRP-strengthened RC slabs which is particularly beneficial in order to produce safer structures. An analytical model is then developed which is based on a novel quad-linear moment-curvature response which can capture the complete load-deflection response of the FRP-strengthened slabs anchored with FRP anchors. The analytical modeling approach enables closed-form equations to be derived which can then be used by design engineers to relatively easily construct load-deflections responses and accurately predict member responses. Following the concluding comments for the project as a whole, future research topics of relevance are identified. / published_or_final_version / Civil Engineering / Master / Master of Philosophy

Reinforced concrete (RC) columns are the primary load-bearing structural components in buildings. Over time these columns may need to be repaired or strengthened either due to defective construction, having higher loads than those foreseen in the initial design of the structure, or as a result of material deterioration or accidental damage. Three external strengthening methods, namely steel jacketing, concrete jacketing and composite jacketing, are commonly adopted for upgrading the ultimate load capacity of RC columns. Among these strengthening techniques for RC columns, steel jacketing, which is easy to construct, less prone to debonding and has better fire resistance than bonded plates, has been proven to be an effective retrofitting scheme and is the most commonly used. Different methods for strengthening existing RC columns have been proposed in the literature. However, no matter which jacket is used to strengthen RC columns, the adverse effects of pre-existing loads on stress-lagging between the concrete core and the new jacket have yet to be solved. In order to deal with this problem, a new postcompression approach was proposed for strengthening preloaded RC columns. In this approach, the slightly precambered steel plates were used. The advantages of this ‘post-compressed plates’ (PCP) strengthening technique are that both the strength and deformability of existing columns can be enhanced and the design life of old buildings can be prolonged. Due to the aforementioned advantages, the PCP strengthening technique was investigated in this study. To begin with, axial compression tests of the PCP strengthened columns were conducted. The overall response, in particular the internal force distribution between concrete and steel plates was obtained. It was observed that the plate thickness and preloading level had dominant effects on the behaviour of PCP strengthened columns. Subsequently, eccentric compression tests of PCP strengthened columns were undertaken. The behaviour of PCP strengthened columns was mainly affected by the degree of eccentricity and plate thickness. Placing flat and precambered steel plates on the tension and compression sides respectively of the RC columns and using post-compression method on the compression side can significantly improve the ultimate load capacity of RC columns under large eccentricity; while placing precambered steel plates on the side faces of the RC columns can significantly improve the ultimate load capacity of RC columns under small eccentricity. Finally, axial compression tests of PCP repaired fire-exposed columns were carried out. The ultimate load capacity of fire-exposed columns can be restored up to 72% of original level by using this post-compression approach. The corresponding theoretical models were also developed to predict the ultimate load capacity of PCP strengthened columns. Comparison of theoretical and experimental results showed that the theoretical models accurately predicted the load-carrying capacities of PCP strengthened columns. According to the experimental and theoretical results, a unified design procedure for the PCP strengthened columns was proposed to aid engineers in designing this new type of PCP strengthened columns and to ensure proper column detailing for desirable performance. The design procedure was validated by the available experimental and theoretical results. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy