Numerical Analysis And Optimal Design For Demolition Of Urban Bridge Blasting

Nowadays,the demand of people for vehicles is growing rapidly,which has brought great pressure to the current transportation industry.The time of bridge construction in many cities is relatively early,which can no longer meet the current traffic volume and modern urban planning,so it needs to be demolished.In recent years,blasting demolition technology is more and more used in bridge demolition engineering because of its excellent effect in bridge demolition.In the early stage,it mainly relies on experience and belongs to the "extensive type".With the increase of bridge blasting engineering,different bridge structure characteristics and blasting requirements are more and more strict,gradually changing to "refined".It is very important to use computer to simulate the blasting effect of bridge,optimize the design scheme and realize the expected blasting effect of bridge in modern bridge demolition engineering.Based on the explicit dynamic FEA software ANSYS/LS-DYNA,the whole process of blasting collapse of urban bridge is simulated and compared with the actual blasting effect.The results show that the numerical simulation of blasting demolition of urban bridge is reasonable and feasible,which is consistent with the actual effect.The analysis results provide the basis for the feasibility of the blasting scheme.The main contents are as follows:1、By analyzing the collapse characteristics and instability modes of different types of bridges,and combining the advantages of various blasting techniques in bridge demolition,this paper analyzes the instability mechanics model and collapse motion model of urban bridge piers with different structural forms,and studies the ground vibration formula caused by bridge blasting touchdown.2、By using ANSYS/LS-DYNA software,building a urban bridge model by using the separated common node model.The reinforcement and concrete are regarded as elastic-plastic materials.and*MAT_BRITTLE_DAMAGE in LS-DYNA is used to simulate them.The concrete unit and ground unit are simulated by SOLID 164 unit,and the reinforcement unit is simulated by BEAM161 unit.The blasting of pier is realized by setting the failure time of materials,and discussed in detail the whole process of bridge collapse.In this paper,the stress,movement track,collapse speed and ground vibration caused by bridge touchdown are compared and analyzed under different blasting schemes.3、According to the blasting effect of numerical simulation and the actual blasting demolition cases of urban bridges,a reasonable blasting demolition scheme is formulated.The feasibility of the optimized design scheme is verified by comparing the actual blasting effect with the numerical simulation effect.