Evaluation of Deflection Amplification Factor for Special Moment-Resisting Frame with Shear Wall under Critical Strong Ground Motions with/without Successive Shocks

In most seismic design codes, lateral loads are reduced by applying the response modification coefficient in the linear static analyses. Hence, the lateral displacements of the structure should be increased to obtain a realistic estimation of the actual displacements. In this regard, static drifts are multiplied by a deflection amplification factor (Cd). This factor is proposed based on single earthquakes in seismic codes such as ASCE 7 and Standard No. 2800 (4th Edition) while structures in seismic regions will typically be exposed to a number of aftershocks after a major earthquake. Since, the repair of the structures will not be practically possible before exposing to aftershocks, ensuring the proper performance of structures under successive earthquakes is essential. Accordingly, in this paper, deflection amplification factor has been evaluated for dual system of special moment-resisting frame with shear wall under critical seismic sequences. For this purpose, 3 RC building frames with the number of 3, 7 and 11 story have been subjected to linear static, linear and nonlinear dynamic analyses and the deflection amplification factor has been calculated and extracted for each of them under two states of successive and single earthquakes. The results show that successive shocks do not significantly affect the Cd compared to a single earthquake. In addition, a supplementary study has been performed for a number of single earthquakes (near-fault earthquakes which have been introduced in FEMA P695) to provide more reliable results. This investigation reveals that the proposed values in ASCE7-16 and Standard 2800 are not sufficient for Cd coefficient.