Development and performance of a ductile shear tie for precast concrete insulated wall panels

This paper presents the development and experimental evaluation of a new ductile shear tie system for precast concrete insulated wall panels subjected to large flexural demands from blast or impact loading. The ties develop a stable plastic hinge mechanism with a multi-legged design, enabling larger inter-wythe shear deformations without sacrificing structural integrity. The performance of these ties is assessed in conjunction with two types of rigid insulation, extruded (XPS) and expanded polystyrene (EPS), that are commonly used for insulated precast concrete facade panels. Shear test specimens with either bonded or unbonded insulation layers were both fabricated to determine the individual contributions of the shear ties and insulation to the total shear strength. A double shear experimental test procedure is proposed to mechanically emulate the flexure-induced behavior of shear ties in insulated wall panels. A series of shear tests was conducted, first under semi-static loading and then at higher strain rates to quantify shear resistance of panels subjected to blast loading. A qualitative comparison is made between failure mechanisms of XPS and EPS insulation, and the new tie is able to achieve a reliably high level of shear deformation ductility relative to other commercially available ties. The shear resistance backbone curves obtained from this study can be used as input for enhanced design and analysis of precast concrete insulated wall panels to resist blast loading.