Responses of cold-formed steel storage racks with spine bracings using speed-lock connections with bolts II: Nonlinear dynamic response history analysis

The objective of this paper is to investigate the seismic response of cold-formed steel storage racks with spine br acings using two types of connections: a speed-lock connection, JD1, and a speed-lock connection with two bolts and full flange welding, JD5, using the incremental dynamic analysis (IDA) as a companion paper to the pushover analysis. The racks analyzed are racks using only JD1 and JD5 connections given the insights in terms of their performances observed from the pushover analysis in the companion paper. This paper presented the structural models for the IDA analysis with the hysteretic behaviors of the connections based on the previous experimental studies. With selected ground motion records, a total of 44 IDA curves were produced for each rack model studied: a single entry unit rack (SEU) and a double entry unit rack (DEU). The impact of the ground motion records was studied based on the IDA and associated fractile curves. The response modification factor R were then calculated for each rack and compared with those from the pushover analysis. The collapse mechanisms were also studied from the IDA results and compared with those from the pushover analysis. Moreover, the seismic performances of the racks were evaluated based on nonlinear dynamic response history analysis under the ground motions that were closely matching with fractile curves.