Global performance of multi-story stiffness-eccentric RC structures subjected to progressive seismic excitations : shaking table investigations

Asymmetric structures have demonstrated poor seismic performance while experiencing major earthquakes in the past. Such structures exhibit complex vibration characteristics under seismic shaking as there is coupling between the lateral and torsional components of vibration. These coupled vibrations tend to cause weak locations under torsional distress, which eventually leads to the global failure of the structure. This paper presents the experimental evaluation of a plan-asymmetric structure with stiffness eccentricity. The experimental investigation was conducted by means of shake table testing on a 1/4-scaled reinforced concrete (RC) frame shear wall structure exposed to progressive seismic excitations. The structural response is monitored from a global failure perspective both in the elastic and inelastic states under increased torsional vibrations. The experimental findings indicate that: (1) irregularities in a structure can lead to significant amplification of the dynamic response due to induced torsional vibrations (2) the damage in the structure influences the dynamic properties of the structure, which eventually tend to influence the global structural response (3) structural acceleration response is more sensitive to seismic excitations and appears to have more influence on local oscillations compared with structural displacement response and (4) floor rotations excessively increase with the increasing damage state of the structure. Based on the physical inspection and extracted measurements, the shear wall sustained severe damage, whereas beams and columns at the flexible edge of the structure formed plastic hinges in critical zones.