Fayaz Rahimzadeh Rofooei

The behavior of Cold‐Framed Steel (CFS) frames under earthquake loads must be examined before CFS building systems can be integrated fully into the construction market. Over the past 20 years, studies have focused on the subsystem level, while system‐level performance has been less studied. This paper aims to bridge the gap between subsystem and system‐level performance. In this regard, a full‐scale shake‐table test is conducted using results from subsystem‐level tests to provide experimental insight into the behavior of real 3D CFS‐framed structures under seismic excitation. The CFS‐framed building is designed in accordance with the Iranian Cold‐Formed Light Steel Structures Design and Construction Code. The building's structural system comprises CFS, CFS‐framed shear walls with two‐sided and one‐sided sheathings, and a k‐brace for lateral force‐resisting shear walls. The CFS test structure features a rectangular floor plan measuring 2.9 m × 3.10 m, with a uniform story height of 2.4 m throughout all levels. Using signal‐processing techniques, the frequency response function of the CFS specimen is determined to identify its natural frequencies and damping ratios. The structure is subjected to ground motion tests on the shake‐table. Then, simplified numerical models are developed in OpenSees. Nonlinear time‐history analyses were performed on finite element models of the CFS building, with results systematically compared with shake‐table test data to validate the proposed simplified modeling approach. The developed model demonstrates excellent agreement with experimental results, showing: (1) close correlation in natural period between the numerical model and physical structure, and (2) nearly identical peak story absolute acceleration responses.

The performance of several regression methods is investigated to estimate the distribution of engineering demand parameters conditioned on intensity measures (EDP|IM) for small record sets. In particular, the performance of the multivariate ordinary least squares (OLS), a simultaneous mean-variance regression (MVR) done by a penalized weighted least-square loss function, and a mean-covariance/variance regression based on expectation maximization method (EM) are assessed. The efficiency of the introduced methods is compared with FEMA-P58 methodology. Performance assessment of EM and MVR methods shows that the overall increase in efficiency is about 25–45% for maximum inter-story drift ratios, and 30–50% for maximum absolute floor acceleration.