Salar Manie - Department of Civil Engineering, Islamic Azad University, Sanandaj Branch,Sanandaj, Iran
Abdoreza Sarvghad-Moghadam - International Institute of Earthquake Engineering & Seismology (IIEES),Tehran, Iran
Mohsen Ghafory-Ashtiany - International Institute of Earthquake Engineering & Seismology (IIEES),Tehran, Iran

This paper is an attempt to study the fragility of a low-rise building with mass irregularities in plan with emphasis on collapse region of response. The study evaluates the fragility and collapse response of a three-dimensional 3-story reinforced concrete model with unidirectional mass eccentricities in plan equal to 0% (symmetrical), 10%, 20% and 30% using extensive nonlinear incremental dynamic analyses. Performance of each model is examined by means of calculation of collapse margin ratios (CMRs) and the associated fragility curves. Results demonstrate that substantial differences exist between behavior of torsional (irregular) and non-torsional (regular) buildings in terms of safety margin against collapse and fragility curves. Results indicate that current seismic design parameters could be non-conservative for low-rise buildings with high levels of plan eccentricity and such structures may not meet the design target performance objectives

fragility, irregular structures, collapse, performance-based, low-rise buildings