CFSRC researchers Mohammed Eladly and Ben Schafer working on the CFS-NHERI project investigated the seismic deflection amplification factor (Cd) for a series of archetype buildings employing cold-formed steel framed shear walls. A total of 118 archetype buildings were considered, of which 83 utilize cold-formed steel framed shear walls with steel sheet sheathing and 35 utilize wood structural panel sheathing. Nonlinear time history analyses for the 118 archetype buildings subjected to the 44 FEMA P695 earthquakes was conducted using nonlinear equivalent single degree of freedom (SDOF) models constructed in OpenSees.
Depiction of application of Cd to predict nonlinear peak deflection from a time history
The results show that current practice may over-estimate expected deflections. To address this issue, and to simplify design, a linearization of the AISI S400 deflection expression is recommended, instead of the overly-conservative AISI S400-20 nonlinear deflection expression employed in current practice. The work was summarized at the recent CFSRC Colloquium in this paper, and is under final revision with a journal. A link to the final paper will be added upon publication.
Histogram of predicted Cd across earthquakes and buildings vs. code specified Cd of 4.0