Finite Element Analysis And Simulation For Demolition Of Constructions Due To Controlled Blasting

The application of demolish blasting technique for the city extending and rebuilding is becoming wider and wider in recent years, however , the development of blasting demolition theories is trailed the practice, the design of demolition were mostly based on experiential formula , and at the same time the request to blasting demolition is higher and higher. Demolition technique must be developed to the direction of accurate and controllable. In this paper, the state of blasting demolition technique and numerical simulation for it was reviewed, Finite Element Method combined with the software ANSYS was applied in the analysis for damage and collapse of construction demolition. The achievements are as follows:1) Different methods was used to build the model for the different structures, for great soar constructions such as chimney and water tower, solid elements were used, for frame buildings , 3D model was built with BEAM-SHELL elements.2) ANSYS/STRUCTURE finite element code was applied for statics analysis of a frame building which was modeled with BEAM188 and SHELL163 element. The blasting columns were tackled with "kill element" and the loosing parts were tackled with reduce the elasticity modulus, the effect of span, number of loosing nodes to the damage of structure was studied and reasonable blasting parameters were given.3) ANSYS/LS-DYNA code was applied for collapse simulation of wuhan marketplace and the backward movement was analyzed. Wuhan marketplace was a frame building .3D model was built with BEAM161 and SHELL163 elements and the material of *MAT_PIECEWISE_LINEAR_PLASTICITY, the rigidity decrease negative rigidity was considered. The keyword of *DEFORMABLE_TO_RIGID_AUTOMATIC was used to control the form of blasting cuts, material fail was controlled with plasticity strain. The error was less than 5% in the aspect of collapse time, backward displacement , forward displacement , it show that the model built in this paper is reasonable. The backward movement during structure collapse was due to the large eccentricity of compress, the resist section for compress should be increase to prevent backward movement in thefuture.4) ANSYS/LS-DYNA code was applied to simulate the blasting demolition for a cooling tower which sites in shanxi datang. SOLID164 element and *MAT_BRITTLE_DAMAGE were used to built a integer RC finite element model. Blasting cut and material fail were controlled with the keyword of *MAT_ADD_EROSION , with " time" and " the principal strain" respectively. The cooling tower was narrow in upside and broad in downside, the center of gravity is too low to move out easily, but it was large in volume and weight, it collapse because of the plasticity strain after damage.5) The vibration due to structure drop down should not be ignored during blasting demolition. In this paper, wuhan marketplace was taken as an example for the analysis of fall vibration and the rule of it was studied. Generally, the velocity of vertical is greater than velocity of horizontal, and time-delay blasting technique can be evidently decrease the fall vibration .The results acquired in this paper show that It is feasible to damage and collapse analysis with finite element method (FEM), the numerical model is very important to theory research on blasting demolition.