Damage assessment of structures against blast load based on mode approximation method

Abstract

Damage assessment plays an important role in the evaluation of the stability and strength of structures, which is significant for both the existing structures and those under construction. An effective damage assessment method based on the deformation behavior of a structure is essential in order to apply protective measures when there exists potential blast load risks. For a reinforced concrete structural element, the analysis becomes more complicated because the reinforced concrete always deforms in a nonlinear way, especially in the post-failure stage.

Although it is straightforward to use the single-degree-of-freedom (SDOF) approach to derive the structural response, the SDOF model usually oversimplifies the structural deformation due to the limitation of its mathematical form and ignores the influence of the shear deformation in bending failure. In the present study, the mode approximation method (MAM) is adopted to generate pressure-impulse (P-I) equations and diagrams. According to this method, the shear and bending responses can be considered simultaneously, and the combined failure modes for structural elements are included.

Damage assessment for underground structures is also studied. The soil-structure interactions (SSI) due to external or internal explosion are simplified as damping or stiffness effect and theoretical solutions are derived based on the MAM. To obtain a more accurate theoretical solution and consider the complexities of the material strength and the SSI effect, the MAM has been subsequently extended to use a generalized integration procedure on scenarios of both surface and underground structures. Therefore, the pulse-shape effect and the nonlinearities of material strength and the complicated SSI effect could be considered.