THEORETICAL MODEL FOR HFR-LWC BEAM UNDER BLAST LOADING ACCOMPANYING MEMBRANE ACTION AND ITS EXPERIMENTAL VALIDATION

Membrane effect is regarded as a potential safety factor in current blast-resistance design codes, but the membrane behavior and its contribution to structural resistance are not intensively investigated as yet. Based on the equivalent Single-Degree-of-Freedom (SDOF) method, a theoretical model for beam-like member under close-range blast loading accompanying membrane action is proposed. A special loading device of membrane action is manufactured in this paper, and the blast-resistant tests on 8 Hybrid Fiber Reinforced-Lightweight Aggregate Concrete (HFR-LWC) beams are performed. The overpressure history of shock wave, mid-span displacement and failure pattern of HFR-LWC beam are obtained. The influences of constraint stiffness, scaled distance of explosion and reinforcement ratio on load-carrying capacities and failure modes of HFR-LWC beam are discussed, and then the reliabilities of presented model are validated by blast-resistant tests. It is indicated that the analytical results based on the improved SDOF model are in good agreement with the experimental data, which provides a reliable tool for quantitatively estimating the membrane contribution to structural resistance and predicting the dynamic behaviors of HFR-LWC beam under blast loading accompanying membrane action. The blast-resistances of HFR-LWC beam would be significantly enhanced by membrane effect, and the ultimate resistances of beam-like member might be greatly underestimated if the membrane action is neglected.