Bidirectional Shaking Table Tests of a One-fourth Scale Reinforced Concrete Space Frame

Shaking table tests on the 1/4th-scale three-story reinforced concrete frames were carried out to investigate the effects of bidirectional earthquake motions on overall nonlinear response of reinforced concrete frame buildings. Two identical models were constructed and one was subjected to bidirectional horizontal earthquake motions and the other was subjected to unidirectional one. A series of earthquake input tests with step-by-step increased the intensity were conducted for both models. The two models exhibited the strong column-weak beam collapse mechanism at a same input level where the maximum interstory drift angle was about 1/40 for both models. Until this input level, the story restoring force characteristics under the bidirectional input was almost the same as the one under the unidirectional input. However, at the next input level where the maximum interstory drift angle was about 1/25 under the unidirectional motion, the story shear reductions and the increase of interstory drifts were observed in the bidirectional test compared to the unidirectional one.