Many bridges were constructed before a seismic design provision was implemented in Korea. Therefore, poor seismic response of non-seismically detailed RC bridge columns could be expected during a seismic event. The aim of this study is to report experimental results of a seismic retrofit method for the non-seismically detailed rectangular RC bridge columns by casing lap-splice region with a Stainless Steel Wire Mesh (SSWM) and permeable polymer mortar. Total five reduced scale RC column specimens were tested to examine the seismic performance improvement due to the SSWM wrap casing for retrofitting the rectangular RC columns with an inadequate lap-splice length in the longitudinal reinforcement. The test results show that the non-seismically detailed rectangular RC column has poor seismic capacity. However, this deficient seismic capacity can be upgraded by applying an elliptical shape SSWM wrap and an elliptical shape mortar casing into the lap-splice region of rectangular RC column.

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In this paper, a preliminary design procedure of magnetorheological (MR) dampers is developed for controlling building response induced by seismic excitation. Hysteretic biviscous model which is simple and can describe the hysteretic characteristics of MR damper, is used for parametric studies. The capacity of MR damper is determined as a portion of not the building weight but the lateral restoring force. A method is proposed for the optimal placement and number of MR dampers, and its effectiveness is verified by comparing it with the simplified sequential search algorithm. Numerical results indicate that capacity, number and placement can be reasonably determined using the proposed design procedure.

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