Numerical Analysis And Evaluation On Block Wall Under Blast Loading

Masonry structure has a relatively high proportion in all kinds of buildings and concrete block masonry walls reinforced with rebars are the direction of development of masonry structure in the future. However, masonry component or structure has a relatively low capacity of resistance under blasting loading. Nowadays, explosive events occur frequently and once the masonry structures are damaged under blast loading, it could bring huge loss of human lives and property, resulting in economy loss and instability of social order. Therefore, research on concrete masonry structures to resist blast loading is an urgent need.The paper numerically analyzes dynamic response, failure mode, and collapse mechanism of concrete block masonry walls under blasting loading by using commercial finite element software, and puts forward an evaluation method for the damage level. The main work is as following:(1) The influencing factors for the dynamic response of the concrete block wall are numerically analyzed. The paper focuses on the failure modes and nonlinear dynamic responses of a reinforced masonry wall confined with edge RC columns and a reinforced masonry wall restricted with a transverse wall under various blasting loading. The influencing rules for the masonry walls with variety of mass of explosive, stand-off distance, wall restriction and reinforcement are numerically analyzed. The results show that the shear failures usually happen both at the top and bottom of the wall, and the bending failures usually generate at the middle part of the wall. The side confined RC columns and the transverse wall can effectively reduce the response of the wall and increase the capacity of the wall under the blast loading.(2) The collapse mechanism of concrete block walls under blast loading is numerically analyzed. Three cases which the vertical compression ratios are 0.2, 0.3 and 0.5, respectively, with the same mass and stand-off of the explosive, are numerically developed. The two kinds of collapse modes which are instability-failure and pressure-failure are numerically developed, and the causes and processes of two collapse mechanisms are also analyzed. The numerical results show that the vertical compression ratio has great influence on the collapse modes for the same blast loading.(3) The failure modes of concrete block walls are also simulated and analyzed. The brittle failure, bending failure and joint failure are numerically developed, which the brittle failure is dominated by shear failure. The numerical simulation shows that block walls prone to bending failure under long-range blast loading and prone to shear failure under close range, a large amount of TNT charges equivalent blast loading. However, under normal circumstances, block walls will generate a combined failure with both of bending and brittle failure characteristics.(4) The damage evaluation method for the concrete block walls is put forward. The P-I curves of a single degree of freedom system under three kinds of blast loadings which are the pulse loading, dynamic loading and quasi-static loading, respectively, are deduced. Numerical simulation method is used to draw P-I curve of block wall in this paper. In order to eliminate the size effect of the wall influenced on the P-I curve, the P-I curve of the wall with three different high-thickness ratio is plotted. Some critical damage points of the walls are numerically simulated and determined, then the P-I curve is fitted by the damage critical points.At last, the content of this thesis is generalized and summarized, and some problems which need further study are proposed.