Collapse Behavior of Reduced-Scale Frames by the Inverted Shaking Table Method under Dynamic Seismic Loading

The shaking table test, which is generally conducted using reduced-scale frames to investigate the collapse behavior of structures during underground motion, is an effective method in the seismic engineering field. However, unlike the shaking table test with full-scale frames, those with reduced-scale frames possess several problems owing to the scaling effect. This paper proposes a novel experimental method for performing the shaking table test with reduced-scale frames to overcome these problems; this method is known as the “inverted shaking table.” Through a series of experiments using this method and two earthquake records as inputs without modifying the time axis, the elastoplastic behaviors of reduced-scale steel frames are obtained up to their collapse owing to the P-Δ effect. Additionally, the changes in the collapse process are studied by changing the vertical load on the test specimens. The test results obtained in this study are validated using the response analysis of a single degree-of-freedom system, which reveals that the hysteresis and acceleration multiplier of the input wave obtained using the response analysis and test for each specimen are approximately the same. This indicates that the proposed method is effective for reproducing the frame behavior up to collapse for specimens with portable components and using general experimental apparatus.