Thesis (M. Phil.)--University of Hong Kong, 1987.

Thesis--Ph. D., University of Hong Kong, 1985.

Thesis--M. Phil., University of Hong Kong, 1984.

Thesis (M. Phil.)--University of Hong Kong, 1986.

No description available.

Existing reinforced concrete (RC) beams often need to be strengthened due to material deterioration or a change in usage. The bolted side-plating (BSP) technique, i.e., attaching steel plates to the side faces of RC beams using anchor bolts, effectively enhances the bearing capacity without significant loss in deformability thus receives wide acceptance. However, as a newly developed technique, only limited information is available in literature, which mainly focused on the overall load–deflection performance of lightly reinforced BSP beams. Little studies have been conducted on the partial interaction between steel plates and RC beams which is closely related to the performance of BSP beams. The longitudinal and transverse slips, which control the degree of partial interaction, have yet to be determined precisely. Accordingly, in this thesis, extensive experimental, numerical and theoretical studies on BSP beams are presented. The experimental behaviour of BSP beams was investigated. For the first time, special effort was put in precisely measuring the profiles of longitudinal and transverse slips. In order to investigate the behaviour of BSP beams under other load cases and beam geometries, a nonlinear finite element analysis was conducted. The numerical method is more economical and capable of overcoming the difficulty in measuring the transverse slips precisely. A new approach to evaluating the transverse bolt shear force was also developed through a parametric study. New partial interaction models were developed by isolating and considering the longitudinal and the transverse partial interaction separately. A longitudinal slip model was developed based on the BSP beam section analysis, in which different strains of steel plates and RC beams were considered but the difference in deflection hence the difference in curvature was not taken into account. Meanwhile, a piecewise linear model was also proposed for the transverse slip and bolt shear transfer by introducing Winkler’s model and defining the transverse slip as the difference in deflection. Formulas for the slips, the plate forces, the strain and the curvature factors that indicate the degree of partial interaction, were also deduced. Furthermore, these formulas allow us to evaluate the effect of partial interaction in the BSP strengthening design. A numerical program was originally developed to evaluate the performance of BSP beams with partial interaction. The balance between strengthening effect and strengthening efficiency was also achieved by a parametric optimization study, which would simplify the design procedure of BSP strengthening significantly. According to the numerical and theoretical results, a new design approach for BSP beams, which needs only minor modification to existing design formula for RC beams, was proposed to aid engineers in designing this type of BSP beams and to ensure proper details for desirable performance. Compared to the conventional design methods that assume a full interaction between steel plates and RC beams, this new method not only retains the features such as ease of use and fast calculation, but also yields results that are more reliable. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

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Pretensioned concrete box beams have been used in highway bridges for more than half a century. Due to their geometry, they have often been used as a viable alternative to the classic I-shaped girders. Box beams are highly effective in cases where speed of construction is a priority. However, the detailing and design of box beams are more complicated than that of I-shaped girders. The flow of forces at the beam’s end blocks must be understood in order to detail reinforcement adequately. The following were the objectives of this research study: (i) quantify the demands placed on box beam end blocks upon prestress transfer, (ii) characterize the demands placed on box beam end blocks upon the application of superimposed loads, (iii) evaluate the effects of alternative void geometries at skewed ends of box beams on curing temperatures, (iv) based on the knowledge gained in (i), (ii) and (iii), improve the box beam end blocks, (v) test the improved end block under worst case scenario demands at prestress transfer and under extreme loading conditions, and (vi) validate currently used shear strength design methodologies in their application to pretensioned box beams. In order to achieve these objectives, an experimental program was conducted. The experimental program included the load testing of ten 4B28 and five 5B40 box beams, for a total of twenty nine load tests. The influence of several factors that distinguish box beam behavior from the better-understood I-shaped girder behavior was studied. Additionally, the experimental program included the fabrication, instrumentation and early-age behavior study of five 5B40 box beams. The first three beams were used to vii assess the behavior of box beams fabricated with the current TxDOT standard details (from December 2006). The fourth beam incorporated modifications to the standard reinforcement details based on the observations made through the study of the first three 5B40 box beams. The last specimen corresponded to a new box beam cross section (5XB40) optimized to be used in a spread-box beams configuration. / text

published_or_final_version / Civil Engineering / Master / Master of Philosophy

published_or_final_version / Civil and Structural Engineering / Master / Master of Philosophy