Theoretical modelling for the dynamic responses of RC beams under non-midpoint explosion

Abstract

Dynamic response of a RC beam under close-in explosion is a popular topic in recent few decades, while few researchers discussed the case for the explosion not upon the middle point of beams. This paper proposes a theoretical model for dynamic responses of RC beams under non-midpoint explosions. Firstly, as the maximum deflection point of RC beams under the close-in explosion load always located directly below the detonation point, a concentrated load methodology is proposed, and a formula for calculating the equivalent concentrated load is built according to the principle of equal work done. Secondly, transformation factors are modified according to the position of equivalent concentrated load. The factors including offset distance of detonation point, boundary condition, plastic hinge and complex material behavior are considered in the resistance function calculation and the relationship between the resistance force and the deflection is established. Thirdly, the accuracy of the modified single degree of freedom (SDOF) model is verified through comparison with the experimental data. Finally, the influence of relative offset distance, span-depth ratio and reinforcement ratio on the maximum deflection and supported angle of RC beams subjected to close-in blast loads is discussed. The theoretical model overcomes the limitation of the existing model, which requires the detonation point to be located directly above the mid-span of RC beams. It is more applicable relative to the traditional SDOF model, since the location of the detonation in the accident or war is always arbitrary.