Effect of cyclic loading on composite behavior of insulated concrete sandwich wall panels with GFRP shear connectors

A full-scale experiment was conducted to investigate the composite behavior of insulated concrete sandwich wall panels (ICSWPs) under monotonic loads and wind-induced cyclic loads. The experimental program consists of two groups, according to the applied loading type and the type of insulation, with the same configurations of glass-fiber-reinforced polymer (GFRP) grids. The degree of composite action in terms of the initial stiffness and ultimate strength were compared at the global level, and the degree of composite action in terms of the shear flow were compared at the local level (in accordance with the variables). The test results showed that the adhesive bonds based on the insulation absorptiveness and the mechanical bonds based on the insulation surface roughness and groove treatment were effective for inducing the desired composite behavior of ICSWPs in both monotonic loading and cyclic loading tests. The cyclic test group showed a lower degree of composite action compared to the monotonic test group at a constant rate. This is the case because cumulative fatigue loading damaged the GFRP strands and debonded the interface between the concrete and insulation. These results indicated that the adhesive and mechanical bonds between the insulation and concrete wythes can be used to estimate the design strength of ICSWPs with GFRP shear grids. Additionally, the reduction factor for the design strength by the fatigue effect should be considered in estimation of design strength.