Novel anchorage solution for in-plane decoupling of concrete infill sandwich panels: An experimental study

Abstract

Concrete sandwich panels (CSPs) are widely favored as non-structural infill elements due to their inherent thermal efficiency, acoustic insulation, and ease of erection. However, their rigid connection to structural frames can induce undesirable in-plane force transfer, potentially compromising seismic performance. This study introduces and evaluates a novel, cost-effective flat-duct sleeved rebar anchor system, designed with the dual functionality of providing reliable out-of-plane restraint while minimizing in-plane stiffness transfer. An experimental program was conducted on ten CSP wall specimens (arranged in five pairs) subjected to displacement-controlled cyclic loading. Three pairs for out-of-plane bending and two for in-plane shear. Three top-support configurations were examined: (i) a conventional sliding bearing support, (ii) fixed rebar anchors, and (iii) the proposed flat-duct sleeved rebar anchors. Key response parameters, including peak capacity, elastic stiffness, energy dissipation, ductility, and relative support-wall displacement, were compared. Out-of-plane tests demonstrated that all support systems provided sufficient resistance, with Type 1 (sliding) exhibiting the highest performance. Crucially, both rebar anchor systems (fixed and flat-duct sleeved) maintained connection integrity despite slightly lower out-of-plane stiffness, resulting in some relative displacement between the wall and the frame. In-plane shear tests proved critical in distinguishing the systems. The fixed rebar anchorage (Type (2) transferred significant frame displacement to the infill panel, inducing shear forces that, while small compared to the wall’s in-plane resistance, caused localized concrete cover damage at the connection. Crucially, the proposed Type 3, with its rebar-duct gap, achieved substantial decoupling. Simultaneously, out-of-plane tests demonstrated that the Type 3 system maintained full connection integrity and provided sufficient resistance, comparable to fixed anchors. This work validates the flat-duct sleeved rebar system as a robust, cost-effective, and practical solution for simultaneous out-of-plane restraint and in-plane decoupling, directly addressing the limitations of existing complex details and enhancing the seismic safety of CSP systems.