Seismic Performance Evaluation of Damaged RC Column Retrofitted By Gfrp-Strip Device

Abstract eng:
Many reinforced concrete (RC) buildings, which were designed and constructed with old seismic-design codes, have been seriously damaged and destructed in both destructive earthquakes and several aftershocks. Several aftershocks may be quite destructive because of the previous damage of the RC building. Therefore, demand for development of rapid-repair methods was increased to prevent possible collapse of RC building during the aftershocks. Partial or total collapse of a RC building under the earthquakes was led by the collapse of columns. Therefore, the main purpose of a seismic retrofitting method is to increase shear capacity of the RC columns. In this study, a GFRP-strip device was proposed to improve the seismic performance of damaged RC columns and was designed to consider easy installation and rapid repair. The GFRP-strip device consists of both GFRP composite strips and aluminum clip-connectors. The shape of the aluminum clip-connectors was designed in three pieces to consider easy installation and rapid repair. Three RC specimens consisted of two columns, which were designed at 75% scale of existing school buildings constructed in the 1980s in South Korea, and were constructed to evaluate the performance of the GFRP-strip device. Two of the RC specimens were pre-tested to take damage before installing the GFRP-strip device. After the pre-test damage was done, the GFRP-strip devices were installed along the plastic-hinge regions on both ends of the test columns. The experimental test results indicate several improvements in seismic performance of damaged columns. These include strength enhancement, failure mode, ductility and hysteretic energy-dissipation capacity. Thus, both the maximum strength and ductility of the retrofitted specimens were increased. Furthermore, accumulated energy-dissipation capacity of the retrofitted specimens was increased. Taking the un-retrofitted RC specimen as a control specimen, the failure behavior of the retrofitted RC specimens was changed from brittle-shear failure to ductile-flexural behavior, which was maintained until the failure of the GFRP-strip devices occurred. Finally, it is shown that the proposed GFRP-strip device developed can be used to improve the seismic performance of damaged RC columns.

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