Blast Testing of a Cold-Formed Steel-Framed Building with a Roof Truss System: I. Design, Characterization of Blast Pressures, and System-Level Response

This paper presents the design and measured response of an instrumented 5.49-m×4.88-m single-story cold-formed steel (CFS)-framed building with CFS gabled roof trusses subjected to open-arena blast testing. Although extensive experimental and numerical research has been conducted on the behavior of CFS stud walls and some limited work has been performed on CFS roof trusses under blast loading, all research conducted to date has been performed on individual components. The experiments described herein document the first tests of a complete CFS-framed building subjected to blast loads. This paper presents the configuration and design of both conventional and hardened aspects of the building specimen, instrumentation for measuring the blast pressure and system-level building responses, and the general test program. System identification results are obtained from experimental modal analysis to document the linear elastic dynamic properties of the constructed building specimen. The response of the building specimen is presented for a blast load with large scaled distance to examine the elastic response and subsequently for a blast load with a small enough scaled distance to cause significant damage to the building. Blast pressures measured across the building walls and windward and leeward sides of the roof, as well as those measured in the free field, are presented to document the blast loading and contribute toward addressing the lack of full-scale experimental blast pressure measurements on gable roofs in the published literature. An established semiempirical procedure is employed to investigate the accuracy of predicting blast pressures across the building using simplified methods and to quantify discrepancies between the measured and predicted blast wave parameters on the leeward side of the roof. The system-level response of the building is then examined and the damage observed following the blast test is documented. The measured response exhibited coupled system-level dynamics that have not been considered in prior studies of CFS components under blast loading. The experiment also highlights the importance of considering the negative phase of the blast pressure when evaluating the response of CFS buildings. Observed damage offers unique insight into various limit states encountered in the building system, including the development of web crippling at the end of studs, which has been previously identified as a potential connection failure mode, but has not been well characterized for CFS stud walls subjected to blast.