| Summary: | 碩士 === 臺灣大學 === 土木工程學研究所 === 98 === During the 1999 Chi-Chi earthquake in Taiwan, a large number of old buildings suffered from severe damage or complete failure, and there were thousands of casualties and a great loss of property. A large majority of building collapse resulted from the loss of vertical-load carrying capacities of columns. Most of the damaged columns were found with non-ductile detailing, such as widely spaced hoops with 90 degree end hooks. These columns are known to have poor seismic performance in terms of ductility and energy dissipation capacity. Due to the architecture needs, such as: door, window, etc, the columns are constraint or so called short column. This changes the failure mode from flexural failure to flexural shear failure.
There are several important variables which can affect the strength and behavior of columns, such as longitudinal reinforcement ratio, axial load and hoop detailing. Totally, six full scale specimens were tested under cyclic lateral load with double curvature and constant axial load until failure to observe the behavior of flexural shear and axial failure of columns. Test results show that under different magnitude of axial load, the collapse behavior is different in sense that higher axial load can accelerate the failure process. Columns with larger transverse reinforcement ratio can sustain higher lateral displacement capability, and larger longitudinal reinforcement ratio can enhance the ductility by extending the flexural shear displacement to axial displacement.
The experimentally observed behavior is compared with predicted behavior based on several available analytical models. The Technology Handbook for Seismic Evaluation and Retrofit of School Buildings of NCREE assessment model provides the closest estimations with the experimental results, but with light longitudinal reinforcement columns seem to overestimate the axial failure displacements.
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