Masonry infills are generally assumed as non-structural elements in structural calculations and are not modeled. However, observations after past earthquakes have shown that masonry infills have significant effects on the seismic performance of structures and their seismic behavior should not be neglected. Additionally, the absence of masonry infills in the first story, which is common in structures for commercial and architectural reasons, has led to the occurrence of the soft story phenomenon in past earthquakes. The maximum interstory drift ratio (MD) is the most important criterion for assessing seismic damage and the occurrence of collapse in structures. In this study, the seismic performance of 3- and 9-story steel moment resisting frames (MRFs) with masonry infills was evaluated using a probabilistic framework considering the record-to-record variability. Two configurations were considered for the masonry infills including fully infilled and open ground story configurations. The seismic performance of the MRFs with these two configurations was compared to that of bare MRFs. The OpenSees software was employed for nonlinear modeling of the structures and masonry infills were modeled using single compression-only struts. The fundamental periods of structures with masonry infills significantly increase after the failure of the masonry infills. To evaluate these effects, Rayleigh damping was modeled using the conventional method and a modified method, which considers the severe elongation of fundamental period due the failure of infills, and the responses obtained from the two methods were compared. By performing incremental dynamic analyses using 78 far-field ground motion records, drift margin ratios (DMRs), drift fragility curves and mean annual frequencies of exceeding four MD levels of 0.7%, 2.5%, 5%, and 15% (λ_MD) were obtained for the structures. The MD levels of 0.7%, 2.5%, and 5% correspond to the performance levels of immediate occupancy, life safety, and collapse prevention, respectively. The MD level of 15% corresponds to the seismic collapse of the structures. The results indicate that the presence of masonry infills improves the drift performance of the MRFs with the fully infilled configuration. However, since the masonry infills experience failure at higher drift levels, their effectiveness decreases at these drift levels. Furthermore, the absence of masonry infills in the first story leads to the soft story phenomenon at lower drift levels, and therefore, the performance of the structures with the open ground story configuration is worse than that with the fully infilled configuration. It should be mentioned that at higher drift levels, due to the failure of masonry infills, the structures with the two configurations for infills have almost the same performance and close to the performance of the bare MRFs. The amplification of the soft story phenomenon in the 9-story structure causes the performance of the structure with the open ground story configuration given some drift levels to be even worse than that of the bare structure. For example, by using the modified damping method for the 3-story structure with the fully infilled configuration, the masonry infills reduce the λ_MD value given MD = 0.7% by 43%, but the reduction in the λ_MD given MD = 15% is 19%. Based on the results obtained, the conventional Rayleigh damping method in the technical literature underestimates the responses.

Buckling restrained braced frames (BRBFs) are widely used as a lateral force resisting system due to their advantageous characteristics such as elimination of brace buckling in compression, high ductility and energy dissipation. BRBFs may have damage concentration in one or few stories during severe seismic excitations, because buckling restrained brace (BRB) yields in a certain story and the stiffness of that story significantly decreases. Drift concentration is undesirable as it can lead to general instability resulting from P-Δ effects or residual drift. For controlling damage concentration in one or few stories and achieving a uniform distribution of drifts in all stories, a new system entitled rocking buckling restrained braced frame (RBRBF) can be used. RBRBF system generates uniform story drifts over the height of structure and prevents the damage concentration in one or few stories. Unlike conventional or suspended zipper braced frames, the braces on one side of the braced span along with the adjacent columns and ties are part of a vertical truss system that is hinged at the base and designed to remain elastic until the near collapse limit state is reached. This vertical truss system works as a strong support for preventing damage concentration in one or few stories of the braced frame. The braces on the other side of the braced span are BRBs and are designed to provide energy dissipation. RBRBFs are designed according to a displacement‐based approach. The novelty of this paper is investigating the residual drift performance of this new structural system under the effect of subduction ground motion records, which have higher significant durations compared with crustal ground motion records. In this study, 4-, 8-, and 12-story structures with RBRBF and BRBF systems are considered, and their residual drift capacity values given four maximum residual interstory drift ratio (MRIDR) levels of 0.2%, 0.5%, 1.0% and 2.0% are computed using incremental dynamic analyses (IDAs). IDAs are performed on two-dimensional models of the structures using 22 pairs of short-duration crustal and long-duration subduction ground motion records. After computing the capacity values given these four MRIDR levels, the residual drift margin ratios (RDMR), and the mean annual frequencies (MAFs) of exceeding different MRIDR levels (λ_RD) are obtained. The results demonstrate that all the RBRBFs have better residual drift performance than the BRBFs. Based on these results, the use of RBRBF dramatically reduces BRBF weaknesses including the concentration of damage in a certain story and low post-yield stiffness. For example, the ratios of the total λ_RD value given MRIDR= 2.0% for the BRBF system to its corresponding value for the RBRBF system for the 4-, 8-, and 12-story structures are 21.10, 4.06, and 3.21, respectively. In addition, for most of the structures, as the MRIDR level increases, the ratio of the RDMR value under crustal records to that under subduction records increases.