A damage assessment method for masonry structures subjected to long duration blast loading

With frequent blast accidents of hundreds of tons equivalent explosion, increasing attention has been paid to the damage assessment and anti-explosion safety of building structures. Some evaluation methods give procedures to obtain the pressure-impulse diagrams on the structural components. However, to the best knowledge of authors, how to evaluate the damage degree of building structures as a whole still remains open. In this paper, a weighted component damage method is proposed to evaluate the damage of structures subjected to long duration blast loading. The method, as its name suggests, is to define a damage degree of the whole structure by adding the damage degrees of all components in a weighted manner. The weight of a component, which represents its contribution to the anti-explosion safety, is defined by a strain energy based method. In order to verify the effectiveness of the proposed method, a high-resolution numerical simulation has been performed on a two-story masonry structure subjected to blast loading with a positive phase duration of 100 ms using a self-developed parallel finite element program for shock wave structure destruction simulation. A support rotation criterion based on the flexural deformation model of components is adopted to determine the damage degree of load-bearing components such as brick walls, columns and floors. The damage degree of the whole structure is then obtained using the proposed weighted component damage method. Upon the overpressure-damage curve is obtained, interpolations was carried out to obtain the threshold values of the overpressure corresponding to the six predefined damage levels. The numerical predicted overpressure values were compared with those from literature data. It was shown that the relative error of the overpressure is between -16.9% and 26.2%, and the effectiveness of the proposed method was verified. The proposed assessment approach can be used to obtain the pressure-impulse diagrams of masonry structures and provide effective measures in protecting structures against blast loads.