Cold-temperature-induced thermal stress response of cold-formed steel roof decks

Cold-formed steel roofing systems are susceptible to thermal gradients due to direct exposure to ambient temperature variations. Under cold ambient conditions, roof panels experience thermal contraction. Because the panels are restrained by fasteners and supporting elements such as purlin, this contraction induces tensile stresses along the roof span and shear stresses in the fasteners that transfer forces to the supporting system. This restraint produces nonuniform stress fields across the roof under varying temperatures, which complicates design and performance assessment. Understanding the resulting stress distribution is therefore critical for evaluating overall roof performance. This study examined the thermal response of profiled steel decks under extreme low-temperature conditions. Decks measuring 4.88 m by 0.91 m (16 ft by 3 ft) were exposed to outdoor conditions during extreme winter events. To capture nonuniform thermal stress fields, the specimens were instrumented with distributed fiber optic strain and temperature sensors. The fiber optic sensor layout was designed to measure both strain and temperature variation along the longitudinal deck length caused by thermal gradients. The distributed fiber data were used to develop nonuniform thermal stress fields that characterize the thermal behavior of roof decks. The outcomes of this study will help to understand how cold-temperature-induced thermal stresses in cold-formed steel roofs contribute to cumulative deformation, which is important for design and long-term performance assessment of cold-formed steel structures in cold climates.