Influence of fire on the lateral resistance of cold-formed steel shear walls – phase 2:

Abstract

This report presents experimental investigations of the performance of cold-formed steel lateral force-resisting systems (CFS-LRFS) under combinations of simulated earthquake and fire loading. Three types of shear wall systems are investigated: gypsum-sheet steel composite panel sheathed walls, oriented strand board (OSB) sheathed walls, and steel strap braced walls. Twenty-two 2.7 m tall by 3.7 m long test specimens are subjected sequentially to combinations of mechanical (cyclic shear deformation) and thermal (fire) load. The mechanical loading setup and protocol are based on ASTM E2126 Method C. Fire loads of varying intensity that represent the characteristics of actual fires are investigated. The work is a step toward developing fragility curves (representations of the probability of exceeding a given damage state as a function of an engineering demand parameter) for these systems for use in performance-based design for fire.

Fire resistance of cold‐formed steel framed shear walls under various fire scenarios

“…The measured moisture content of specimens from three randomly sampled gypsum boards was (18.9 ± 0.1) percent by mass. The structural design and detailing of the walls is provided in the NIST report Influence of Fire on the Lateral Resistance of Cold-Formed Steel Shear Walls-Phase 2 16 ; hereafter "NIST report. "…”

“…A complete listing of the thermal measurements can be found in the NIST report. 16 The temperatures relevant to the thermal behavior of the structural elements include chord stud temperatures, interior stud temperatures, sheathing panel temperatures (sheathed walls), and the temperatures between the gusset plates and straps (braced walls). The top interior stud temperature (TC_T_IS) was generally a good overall indicator of the thermal damage to the wall.…”

“…specific fire exposure. 13,14 The results showed that the failure mode shifted from local to global buckling of the sheathing as a consequence of the fire exposure and highlighted the relevance of the gypsum boards on the performance of the walls. 15 The second phase of the study extended the work to two additional types of CFS walls and various levels of fire severity.…”

“…Shear walls (walls with structural sheathing) and strap‐braced walls are structural systems intended to resist lateral (horizontal) forces, such as the ones that occur due to wind and earthquakes. The first phase of the study investigated the performance of gypsum‐sheet steel composite panel sheathed shear walls under a specific fire exposure . The results showed that the failure mode shifted from local to global buckling of the sheathing as a consequence of the fire exposure and highlighted the relevance of the gypsum boards on the performance of the walls .…”

“…15 The second phase of the study extended the work to two additional types of CFS walls and various levels of fire severity. 16 In the second phase, 22 wall specimens were subjected sequentially to various combinations of cyclic shear deformation and fire load. This paper focuses on the fire response of gypsum-sheet steel composite panel sheathed walls, oriented strand board (OSB) sheathed walls, and steel strap-braced walls; the structural response of the walls is reported separately.…”