Experimental characterization of a bolt-based connection for insulated load-bearing precast concrete wall under monotonic and cyclic loading: Effect of wall detailing

The seismic performance of precast concrete modular structures depends strongly on the behaviour of connections, particularly horizontal joints in load-bearing wall structural systems. In lightweight insulated load-bearing wall panels, the insulation layer reduces and interrupts the concrete solid region available for anchorage, altering the local force-transfer mechanism around the bolt and potentially promoting brittle failures such as splitting, cover spalling, or incomplete development of the intended strut-and-tie mechanism. Dry, inspectable, and replaceable connections are essential for improving life-cycle performance, post-earthquake repairability, and functional recovery of modular buildings. Based on this motivation, this study experimentally investigates the monotonic and cyclic tensile behaviour of bolted horizontal connection for lightweight insulated load-bearing wall panels. Twelve specimens, covering four different configurations defined by the solid concrete zone thickness, 100 mm or 200 mm, and the reinforcement layout around the bolt region. The threaded bars were intentionally overdesigned to force failure in the surrounding concrete, allowing the wall-side anchorage capacity and failure mechanisms to be isolated. The response was assessed in terms of damage pattern, initial stiffness, peak strength, ductility, energy dissipation, and damping. The results show that the solid concrete thickness was the governing parameter, namely increasing it from 100 mm to 200 mm increased peak strength by up to 185%, displacement capacity by over 250%, and cumulative energy dissipation by more than 500%. Reinforcement detailing also affected the response, with bars placed closer to the bolt improving energy dissipation by up to 115% and ductility by approximately 23%. These outcomes provide experimental evidence for the design of dry, inspectable, and repairable bolted connections in lightweight load-bearing precast wall systems.