Dynamic Bond Stress-Slip Relationship between Basalt FRP Sheet and Concrete under Initial Static Loading

Reinforced concrete structures strengthened by fiber-reinforced polymer (FRP) always suffer dynamic loadings. Furthermore, the dynamic loadings are always added at the base of static loadings. The success of this strengthening method relies on the effectiveness of the bond of the FRP sheet to the concrete. Although numerous experimental studies have investigated this bond, experimental data concerning dynamic tests on basalt FRP (BFRP) sheets applied on concrete specimens under different initial static loadings are still lacking. This paper presents an experimental investigation on the dynamic bond behavior between the BFRP sheet and concrete under different initial static loadings (0, 30, 50, 80, and 100%) and displacement rate of 70 mm/s. Double-lap shear specimens were used for the tests. The results of the dynamic tests are reported and discussed to evaluate and compare the influence of initial static loading on the dynamic bond behavior between BFRP sheets and concrete. A nonlinear bond stress-slip relationship of the BFRP-concrete interface under different initial static loadings is determined based on an analysis of displacement data, which comprise four empirical parameters, namely, dynamic maximum bond stress tau(d)(max i) under different initial static loadings, corresponding slip s(0), curve characteristic constant n, and local slip s. The test results show that (1) the dynamic bond capacity of the BFRP-concrete interface decreases with increasing initial static loading; (2) the failure mode of all specimens is debonding in the concrete layer; (3) the dynamic effective bond length of the BFRP-concrete interface increases with increasing initial static loading; and (4) the dynamic maximum bond stress decreases with increasing initial static loading. The calculation models of dynamic bond capacity and dynamic effective bond length considering the influence of initial static loading are also presented. (C) 2015 American Society of Civil Engineers.