Structural Performance of Steel Shelf Angles with Thermally Improved Detailing

Abstract

Structural elements that span the building envelope are susceptible to becoming thermal bridges, transferring heat and energy between interior and exterior. This is especially true with steel structural elements. As part of a larger effort aimed at mitigating thermal bridges in building structures, this work focuses on steel shelf angles in steel building structures, a common cladding detail. Steel shelf angles used to support masonry cladding are examples of continuous thermal bridges, because they are integrally connected to the structural system around the building perimeter. With the aim of preventing energy loss and condensation at these steel details, this work addresses the structural integrity of a range of thermal bridge mitigation strategies through combined experimental and computational research. Of particular interest is the structural performance of these steel shelf angle systems with thermally improved shims added between shelf angle and the supporting structural system using snug-tight bolts. Shim material and thickness are varied, along with angle size, bolt diameter, and bolt material. Computational results support the experimental findings that adding thermally improved shims can improve the structural performance of shelf angles under design loads. Design guidance is provided to account for these new variables and limit states.