Evaluation of the seismic performance factors for steel diagrid structural systems using FEMA P-695 and ATC-19 procedures

Abstract

The diagrid structural systems are mainly used for their structural capabilities and architectural aesthetic possibilities which are provided by the unique geometric configurations of these systems. However, the seismic performance factors of these structural systems are not yet explicitly recommended in the existing building codes. In this study, the seismic performance factors (SPFs) of 6- to 24-story steel diagrid structures are determined considering the post-buckling behavior of diagonal members in compression. Also, the effect of change in span length and the diagonal angles on the SPFs of diagrid structures is studied. The ATC-19 coefficient method is used for calculating the SPFs while FEMA P-695 approach is adopted for evaluating the accuracy of the computed factors. Also, the seismic collapse capacity of these structures considering uncertainties in ground motion, modeling, design, and test data is evaluated based on the FEMA P-695 methodology. The OpenSees software is used for modeling and performing the numerical analyses. The obtained results indicate that by increasing the height of diagrid structures, the over-strength, the response modification factor and the median collapse intensity decrease while the ductility factor increases. It is also concluded that the adjusted collapse margin ratios of the diagrid archetypes are larger than the limits suggested by FEMA P-695.