| Summary: | 碩士 === 國立成功大學 === 土木工程學系 === 89 === Precast method can shorten construction time, reduce construction cost and control quality easily. The advantages of hollow cross-sections of concrete columns are material savings and lighter mass. Application of precast method to hollow bridge columns has good potential. The purpose of this research is to study the flexural behavior of precast concrete hollow bridge columns for shear transfer. In the analyses, nine models for the stress-strain relationship of confined concrete are taken into account. In addition, the softened branch relation and effect of low-cycle fatigue as well as shear transfer in the connection region are also considered, so that an analytical model has been derived and the corresponding program has been developed.
With regard to experiment, three parameters are involved, namely, connection method, type of shear key in connection region, and size and amount of tendons. Totally, seven small scale models were tested to investigate the flexural behavior under consideration of shear transfer in the connection region and to examine the analytical model. According to the test results, the dissipated energy of precast columns with shear transfer connection is not less than that of precast columns with connection in plastic hinge region. However, the ductility of precast columns with shear transfer connection are slightly smaller. In other words, precast concrete bridge columns have good seismic performance. The performance of the connection region with shear transferred by shear key and moment carried by presstressing tendons and concrete is excellent. The behavior of specimens with shear transfer connection is similar to that constructed precast method for plastic hinge region, especially in appropriate prestressing tendon force. The failure mode of all specimens is flexural failure. Longitudinal rebars subjected to reversed cyclic loads will have low-cycle fatigue, resulting in local buckling under compression and rupture under tension. When the test results are compared with all nine models, it is found that Confined Kent and Park model provides generally the best simulations. Except the unconfined Kent and Park model, all remaining eight models can also predict the flexural behavior of precast concrete columns for shear transfer.
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