Experimental Study And Numerical Simulation Of Local Damage Of Unreinforced Masonry Under Close-in Explosion

The urban accidental explosion and terrorist bombing attack occur frequently in recent years,which cause severe damage to buildings and structures.At the same time,envelope components of buildings such as unreinforced masonry wall tend to break into sharp fragments with high velocities,which becomes a serious threat to safe of inhabitants and properties in the building.In order to develop design manual and technologies of unreinforced masonry wall against close-in explosion,in this thesis a systematic research on damage pattern and response of unreinforced masonry wall under close-in explosions was carried out based on field tests and numerical simulations.The main research work and conclusions are as following:(1)Field tests on masonry walls under close-in explosions with different scale distances are conducted to study their dynamic response and damage pattern.Sizes of the local damage area are measured and the failure mechanism are analyzed.It is found that crushing damage and spalling damage will occur on front and rear face of the unreinforced masonry wall separately when unreinforced masonry is under blast loads generated by a 1kg TNT explosion,while penetration damage will occur when unreinforced masonry is under blast loads generated by a 6kg TNT explosion.Non-uniform blast loads and its high peak pressure are the main cause of the local damage of unreinforced masonry under close-in detonation.(2)Fragments of the unreinforced masonry wall from the field tests are sieved,classified and weighted.Shape and size distribution characteristics of the fragments are studied based on the distribution function.It is found that the mass proportion of fine fragments in total fragments increases as blast loads increase.Fine fragments account for major proportion in top 1/3 areas closed to the unreinforced masonry wall,while the coarse fragments account for major proportion in bottom 2/3 areas far away from the unreinforced masonry wall,which indicates that the fine fragments have high ejecting velocities.Size distribution of the fine fragments of unreinforced masonry wall under close-in explosion follow a Weibull distribution.(3)Masonry material model and erosion criterion is adapted in LS-DYNA to conduct numerical simulation of damage pattern of unreinforced masonry wall under close-in explosions.The method firstly simulates the interaction process between the blast wave and the unreinforced masonry wall using algorithm of fluid-solid coupling.Then the erosion algorithm is adopted to simulate the local damage of unreinforced masonry wall under the applied blast loads.The numerical method is finally validated by comparisons of the numerical results with the test results.