Continuous Simulation On Collapse In Large Scale Structures Demolition Blasting

The collapse of structure during demolition blasting of large-scale construction is a complicated dynamic problem. It will play significant role in blasting construction if computer can thoroughly simulate the whole process from local failure to destabilization and then to collapse. This paper employed Finite Element Method(FEM), Multi-body Dynamics and Discrete Element Method(DEM) respectively to simulate collapse of structures in different demolition blasting projects according to the characteristics of the three simulation methods. So the continuous simulation could be realized. The main research contents of this paper are as following:1,The Multi-object Modeling technique was put forward,and then the localization of FEM in simulating big movement of structures collapse was broken through using the technique. The Explicit of ABAQUS has been used to carry out finite element analysis of structure collapse during demolition blasting and simulate the whole course. And then the simulation and actual blasting results have been compared from duration of collapse, height and length of blasting muck piles, the differences were just between 4.5% and10%.2,The demolition blasting of building is achieved through destroying key weight bearing part of building to make it lose carrying capacity and then fall down due to gravity function. This process is a course of transferring from the static equilibrium system to the multi-body dynamic system. In order to analyze the whole process of demolition blasting of a building, it is necessary to study the demolition object on aspect of structure as well as on the other aspect of mechanism. In view of this, a multi-body system from the stability-losing structure is abstracted and a model of multi-body system is set up, and then we should make use of computer technology to calculate the model of multi-body system to simulate the collapse processes and results of the same buildings and structures based on various blasting designs.Based on the simulation results, the blasting design can be optimized. The steps are as follow:(1) It abstracts a simple structure from the prototype of building through simplifying; (2) It determines the configuration of the stability-losing structure (3) It abstracts a multi-body system from the stability-losing structure and sets up a model of multi-body system; (4) It makes use of computer technology to calculate the model of multi-body system and obtain simulating results for collapsing building at each stage, and finally acquire parameters about the entire process of collapse of building, the scope of collapse and height of pile-up through a series of cycle processes.3,The Solid Lattice Model(SLM)has been built based on Finite Element Method within the framework of Discrete Element Method. The beam element has been introduced to simulate the interaction of each block, which promoted the contact algorithm of Discrete Element Method and solved the crucial problem in blocks contact found through the Discrete Element Method. The failure criterion of "beam" has been set up. The software system for simulating structure collapse during demolition blasting was developed based on the VC++ platform and combined with STL database. Visual module was developed based on OpenGL Graphic Library. The theory model and program which were adopted in demolition blasting construction have been modified by comparison of simulation and actual resultsThe SLM refers to using polyhedral elements to discretize the object and applying the contact detection method to determine neighbor elements [6] of each block element, and then establishing "beams" between neighbor elements (see Fig.7). By this way, a network of "beam" (see Fig.8) in the whole medium is formed. The dimension of cross-section of "beam" is the same with public contact surface and its length is the distance between two centroids. Each block element is the smallest unit when media granules break, and we use the discrete element method to describe contact action of block element and its motion. SLM is to use this beam net to describe the strength performance of the medium. Through relative locations of cells, beam's transformation can be calculated and according to the transforming situation, whether the beam exists can be distinguished. If its deformation overruns the threshold value, the beam disappears and the connection between two cells is gone. Otherwise, beam exists with transformation. More beams got disappeared and with the accumulation of structure failure, the structure demolishes and collapses at last.The results induced as follow:(1)Overcome the disadvantage of traditional Finite Element in simulating big movements of structure when it collapses. And SLM can not only simulate structure from destabilization to collapse but also portray the course of individual fly away from matrix in detail. (2) Silhouette of blasting muck pile can be shown during structure collapse and it is critical for demolition blasting.