Seismic assessment of a dual concentrically braced steel structure under near-fault ground motions

In this paper, the ‎seismic performance of ‎a five-story steel ‎structure with a dual ‎system used as a lateral load resisting system ‎comprised of a moment-resisting frame ‎and a concentrically ‎braced frame is ‎evaluated ‎under near-field ground motion ‎records with and ‎without pulses. This research paper aims to ‎evaluate ‎the pulses’ ‎effects ‎on ‎the ‎probability ‎of ‎the ‎collapse, global ‎damage index, ‎and the ‎annual and 50-‎‎year collapse risks of ‎the ‎structure ‎with such dual ‎systems, which have been less ‎considered‎ in previous ‎research works. To this ‎end, ‎incremental ‎dynamic ‎analyses ‎are ‎performed, and to ‎determine the ‎probability that the ‎studied structure ‎will ‎exceed a specific ‎damage state, ‎fragility ‎functions are ‎developed. ‎The ‎global damage index ‎of the structure is also ‎computed, and a full ‎assessment of the ‎collapse risk of the ‎structure is carried ‎out under the ‎near-field ‎ground ‎motion ‎records ‎with ‎and ‎without ‎pulses. ‎Finally, It is ‎concluded ‎that ‎the ‎probability ‎of ‎ ‎collapse, global ‎damage index, ‎and the ‎annual and 50-‎‎year collapse risks of ‎the ‎‎structure subjected ‎to ‎the ground ‎motions ‎with pulses ‎are ‎higher than the ‎ground ‎motions ‎without ‎pulses. For the pulse periods larger than two times the period‎ of the ‎first ‎mode of the ‎structure, ‎the ‎intensification occurs due to the equalization ‎of the increased period of the first mode of the ‎structure and the ‎period of the pulse.