Study On The Mechanical Properties Of Concrete Masonry Wall Under Blast Loading

In recent years, the terrorist bombing to the politics, economy, environment and people's lives and property caused a great destruction all over the world. Terrorist attacks commonly occur in densely populated buildings and important political, economic and military influence buildings. These buildings are usually frame structure filling with Concrete Masonry Unit (CMU). When explosives in the building where near explosion, will lead to walls and windows damaged, the flying wall in pieces (block) will make internal casualties. In order to study the response mechanism of masonry wall under blast load, in this paper, finite element analysis software ANSYS/LS-DYNA will be used to establish the effective analysis model, and will simulate the deformation and failure modes of CMU wall under blast load. And will study the failure mechanism of CMU wall retrofitting with Polymer sheet material under blast load.The results show that:(1) The material model and parameters used in this paper, such as concrete block material constitutive model (MAT96) and polymer sheet material constitutive model (MAT24) and the contact model(TIEBREAK) between block and block and also the tensile and shear strength (separately for 0.3MPa and 0.4MPa), the friction coefficient(0.7) after taking cracking, can good simulation the actual situation of concrete masonry wall under blast loading; (2) It is almost no threatening to people in buildings when the peak pressure of blast loading is less than 0.385MPa; When the peak pressure is greater than 0.385MPa, along with the increase of peak pressure, the speed of block aerosol propellant for buildings is increasing, and also gradually increasing internal threats of buildings, and needing retrofit; (3) When the peak pressure AP≤0.95MPa, polymer sheet materials can have very good protection effect, can largely prevent the aerosol propellant scattered block; When peak pressure AP>0.95MPa, Polymer sheet thoroughly fracture, polymer sheet and blocks are propelling into building together; (4) Compare with unretrofited and retrofitted concrete masonry walls, the displacement is reduced slightly, and midspan speed has hardly changed; (5) Through the analysis about the stress and strain of polymer sheet under different load conditions, found that the peak stress and strain all appear in the anchorage when peak pressure△P<0.95MPa, especially when peak pressure near 0.95MPa, the elements near the anchorage happening ruptures; Secondly appeared in the midspan, the biggest stress and strain is about 20MPa and 60% respectively, other parts of the stress and strain less than 20MPa and 60% respectively. (6) Calculated the effective standoff distance of unreinforced wall and reinforced wall with Polymer Sheet when the TNT equivalent are 1000kg,500kg, 225kg and 100kg cases.