Structural and Thermal Performances of Shelf Angle Connections with Innovative Detailing

Abstract Steel through bolts have been conventionally used by the construction industry to anchor shelf angles to a wooden frame system. However, these fasteners are uneconomical, time-consuming, and result in poor thermal performance, since they need to penetrate the entire building envelope. This research investigates the use of lag screws as a novel alternative fastener for anchoring shelf angles to spruce–pine–fir wood-framed structures and evaluates their structural and thermal performance through comprehensive experimental testing and finite-element analysis. Furthermore, the study explores the application of fiberglass stand-offs to facilitate continuous exterior insulation and mitigate thermal bridging, which has not been addressed in previous investigations. The results indicate that through bolts had a higher load capacity per fastener compared to lag screws, primarily due to their longer embedment length. However, both types of connections demonstrated sufficient load capacity to support the design load of the bearing structure. Through-bolt specimens, however, showed greater midspan deflection and rotation. Furthermore, finite-element analysis revealed that through-bolt connections had the lowest thermal performance among all the connections studied. In contrast, lag screws effectively disrupted the heat flow associated with the thermal bridge in the through-bolt connection, highlighting their potential to improve energy efficiency in wood-framed facade systems.