Seismic performance of a 3-story RC frame in a low-seismicity region

Abstract

The objectives of the research stated herein are to investigate the seismic performance of a 3-story reinforced concrete (RC) ordinary moment-resisting frame, which has not been engineered to resist earthquake excitations, and to evaluate the reliability of the available static and dynamic inelastic analysis techniques. A 1:5 scale model constructed according to the Korean practice of nonseismic detailing and the similitude law was subjected to a series of the shaking table motions simulating Taft N21E component earthquake ground accelerogram. Due to the limitation in the capacity of the used shaking table, a pushover test was performed to observe the ultimate capacity of the structure after earthquake simulation tests. The model showed the linear elastic behavior under the Taft N21E motion with the peak ground acceleration of 0.12 g , representing the design earthquake in Korea. The model revealed fairly good resistance to the higher levels of earthquake simulation tests though it was not designed against earthquakes. The main components of its resistance to the high level of earthquakes appear to be (1) the high overstrength, (2) the elongation of the fundamental period, (3) the minor energy dissipation by inelastic deformations, and (4) the increase of the damping ratio. The drifts of the model under these tests were approximately within the allowable limit. Analysis of the results of the pushover test reveals that the model structure has the overall displacement ductility ratio of 2.4 and the overstrength coefficient of approximately 8.7. The evaluation of the accuracy of analytical simulation by IDARC-2D leads to the conclusion that while global and local behaviors can be, in general, simulated with limited accuracy in the dynamic nonlinear analysis, it is easy to obtain a fairly high level of accuracy in the prediction of global behavior in the static nonlinear analysis.