Pure-bending yielding dissipater for the seismic retrofitting of reinforced concrete buildings with soft-story irregularity

Abstract

Removing masonry infill walls from the ground or lower stories of buildings to make more open spaces, may lead to forming soft-story structural irregularities. Since considering the masonry infill walls as non-structural components is a common assumption in the evaluation of the seismic demand of buildings, there is a lack of knowledge dealing with the influence of the soft-story effect on the seismic response. In this study, the performance of 4-, 8-, and 12-story moment-resisting reinforced concrete frames with and without a ground soft story is compared first. Then, a proposal including the use of a yielding dissipater device to retrofit soft-story buildings is presented. The low cost, the simple manufacturing technology, and the same behavior in tension and compression, which makes the new axial force not imposed on the columns, are some of the advantages of this device. In order to assess the seismic performance of the proposed system, incremental dynamic analysis was conducted on the frames. Five states were considered for each frame: (a) bare frame, (b) fully-infilled frame, (c) ground soft-story frame, (d) and (e) retrofitted frames with two different configurations of yielding dissipater devices in the ground soft story. The responses of the structures are compared in terms of capacity curves, progressive damage curves, inter-story drifts, and story damage values. The results demonstrate that the frames equipped with the yielding dissipater devices experience higher lateral load capacity, lower overall damage, lower drift, and a lower damage value in the ground story than the soft-story ones.