Seismic Analysis of the 10-Story CFS-NHERI Building

A 10-story full-scale cold-formed steel building is scheduled to be tested on the newly upgraded 6-DOF Large High-Performance Outdoor Shake Table (LHPOST6) at the University of California San Diego serving as the capstone effort to the NSF-funded Collaborative Research: Seismic Resiliency of Repetitively Framed Mid-Rise Cold-Formed Steel Buildings (CFS-NHERI) project. In preparation for this test program, a simplified pancake model is developed in OpenSees to predict the dynamic characteristics and to simulate the behavior of this 10-story test building under nonlinear dynamic response history analysis. The pancake model is composed of rigid diaphragms and nonlinear shear springs representing the hysteretic behavior of the lateral load resisting shear walls. Pinching4 material properties calibrated using past experiments defined the properties of shear springs with scaling based on geometric properties. To evaluate the robustness of the approach, a similar model of a 6-story CFS building, tested under uni-directional shaking was also developed. For the 6-story modeling effort, the dynamic characteristics and response under the same series of ground motions used in the shake table tests are compared with the test results and good agreement is observed. Thus, for the 10-story CFS-NHERI building (pre-test) analyses, a suite of 22 far-field ground motion pairs provided in FEMA P695 are chosen to perform nonlinear response history analysis. The responses under these scaled ground motions are compared to investigate the effect on the seismic response of the 10-story CFS-NHERI building. In future work, the responses of the pancake model will be compared with other numerical models being developed by fellow researchers within the CFS-NHERI team using more complex wall line representations for example. At present however, it is recognized that the simplified pancake model provides a fast computational turnaround time, while effectively capturing the characteristics and providing reasonable estimates of the responses, which makes it useful for pre-test analyses to identify a candidate suite of ground motions to be used for the future shake table test program.

Proceedings of the Cold-Formed Steel Research Consortium Colloquium.