Blast Testing of a Cold-Formed Steel-Framed Building with a Roof Truss System: II. Component-Level Response

Abstract

This paper presents the measured responses of components—blast wall, shear walls, deep beam and bottom chord bracing, and a roof truss—of an instrumented full-scale cold-formed steel (CFS)-framed building subjected to open-arena blast testing. The objective of this test program is to provide a rich data set to inform future research, analysis, and design of these building components for structures that may be subjected to blast loads. A companion paper presents the blast loading, system-level responses, and observed damage, while this paper focuses on component-level responses. The behavior of the blast wall was examined through instrumentation of the central stud with linear variable differential transformers (LVDTs), shock accelerometers, and strain gauges. Additionally, load cells installed at several anchors connecting the bottom track of the blast wall to the foundation recorded hold-down forces along the wall developed during the test. In-plane displacement vectors and time histories for points on one of the shear walls were obtained from high-speed video, while a load cell positioned at an anchor at the bottom track of the shear wall was used to investigate hold-down forces at the shear wall. Forces in the bottom chord bracing of the roof diaphragm were studied through strain measurements. Lastly, the behavior of the roof truss was studied using measurements obtained from an array of LVDTs, shock accelerometers, and strain gauges mounted on the central truss. The results and single-degree-of-freedom (SDOF) analyses serve to provide greater insight into component-level responses, interactions between building components and subcomponents, and evidence of component and connection behaviors that have not been previously documented in the published literature for CFS-framed buildings subjected to blast loads. The performance of the building components and supporting SDOF analyses demonstrate significant energy absorbing capacity of conventionally constructed CFS stud walls that exceed established performance criteria in current design standards and offer experimental observations to support future development of performance criteria for CFS shear walls and roof trusses, which currently do not exist.