Incremental dynamic analysis and FEMA P695 seismic performance evaluation of a cold‐formed steel–framed building with gravity framing and architectural sheathing

Abstract

Summary The objective of this paper is to present incremental dynamic analysis (IDA) and seismic performance evaluation results for a two‐story cold‐formed steel (CFS)–framed building. The archetype building was designed to current U.S. standards and then subjected to full‐scale shake table tests under the U.S. National Science Foundation Network for Earthquake Engineering Simulation (NEES) program. Test results showed that the building's stiffness and capacity were considerably higher than expected and the building suffered only nonstructural damage even at excitations in excess of Maximum Considered Earthquake levels for a high seismic zone. For the archetype building, three‐dimensional finite element models at different modeling fidelity levels were created using OpenSees. The models are subjected to IDA using the far‐field ground motion records prescribed in Federal Emergency Management Agency (FEMA) P695. Seismic performance quantification following the FEMA P695 procedure shows that if the modeling fidelity only follows the state‐of‐the‐practice, ie, only includes shear walls, unsafe collapse margin ratios are predicted. State‐of‐the‐art models that account for participation from CFS gravity walls and architectural sheathing have overall performance that are consistent with testing, and IDA results indicate acceptable collapse margin ratios, predicated primarily on large system overstrength. Neglecting the lateral force resistance of the gravity system and nonstructural components, as done in current design, renders a safe design in the studied archetype, but largely divorced from actual system behavior. The modeling protocols established here provide a means to analyze a future suite of CFS‐framed archetype buildings for developing further insight on the seismic response modification coefficients for CFS‐framed buildings.

Seismic Evaluation of a 2-Story Cold-Formed Steel Framed Building using ASCE 41-17

“…In contrast, if the shear walls and all the gravity framing (unsheathed) were considered, the collapse probabilities were acceptable -suggesting ASCE 7 response modification factors ( and Ω ) are justified. Moreover, if the final building, with sheathing, non-structural walls, and finish systems, was considered, the collapse probabilities were acceptable by an even wider margin and the structural analysis was in line with the shake table test results [19]. Essentially, for this building, and likely this building system type, ASCE 41's lack of an "easy switch" to account for system overstrength in the linear assessment procedure is an important reason that it's linear analysis method provides such pessimistic predictions of performance.…”

“…The overall building response involved only minor damage even for seismic excitations in excess of ASCE 7's maximum considered earthquake levels [17]. Subsequent nonlinear time history analyses further demonstrated that while the building was efficiently designed with respect to ASCE7/AISI S400 (i.e., design demand/capacity ratios for the shear walls generally near 1.0), the building had substantial strength reserve and more than acceptable collapse probabilities [18,19].…”

Design and process optimization of combined medical and elderly care services: An integrated service blueprint–TRIZ model

“…The service blueprint is a two-dimensional description of the service process, which divides the service process into three parts (patient actions, front-stage action, and back-stage action) to identify the line of interaction and line of visibility. This allows for a clear understanding of the interactions and influences among the different parts of the service process (15)(16)(17) while enabling the visual analysis of the root causes affecting the service perception and satisfaction of the elderly population (18).…”

Seismic performance of mid-to-high rise modular steel construction - A critical review

“…The sheathed steel stud walls were simplified to equivalent cross braces and the model was verified to be reasonable for further incremental dynamic analysis (IDA). Leng et al [ 124 ] demonstrated the necessity of modelling the gravity system and architectural sheathing for the CFS framed building by experiment and non-linear IDA. Annan et al [ 125 ] investigated the seismic vulnerability of 2-, 4-, and 6- story MSC via incremental dynamic analysis (IDA), and demonstrated a satisfactory performance of MSC at designed intensity levels.…”