Simulation Study On The Collapse Process Of Multi-story Building Demolition Blasting

Own to the advantages of convenience,high efficiency and speed,blasting demolition of buildings has become the first choice in the current demolition works.In order to ensure the accuracy of blasting demolition,it is necessary to strengthen the research on the theory of blasting demolition.This paper reviews and summarizes the development process and research status of controlled blasting demolition,the common finite element program ANSYS/LS-DYNA is used to establish the model of common node separation to simulate the collapse process of blasting demolition.The following three contents are the main work of this paper:(1)This paper briefly introduces the ground vibration which is the major disasters caused by blasting demolition.Through analyzing seismic value which is measured when Hubei Yunhe building & Yinfeng hotel was demolished by blast,it is proved that the peak value is larger and the frequency is smaller,and vertical vibration is more violent than the horizontal direction.Although the vibration attenuation of blasting demolition is faster and this ground motion is limited in scope,it is possible to cause damage to the structure within the scope of influence due to the larger peak.(2)Dividing the model structure into different grid size,the author analyzes the influence of structural collapse which is caused by “unit size effect” due to material failure mode.It is pointed out that the smaller unit size is conducive to the simulation of the collapse process more in line with the actual situation.In order to reduce the number of units and save calculation time,it is feasible that the quality of filling wall can be equal to the floor density.In this paper,the influence of the filling wall on the collapse process of the structure is compared,and the study shows that the simplified filling wall has less influence on the simulation of the collapsing process after blasting.At the same time,it can improve the computational efficiency.(3)Taking blasting demolition of Wuhan traffic school training building as an example,using ANSYS/LS-DYNA to reproduce the structure collapse process,this study show that the simulation results are similar to the measured values.Regarding notch height and time delay initiation interval as variables,9 different blasting demol-ition schemes are set up for Wuhan traffic school training building.The comparison of the different cutting height and initiation time interval on the collapse process of frame and structure of rush distance,recoil distance,touchdown vibration is completed.Using 2 different variables(overall structural kinetic energy and unit speed)to compare ground vibration which is caused by different blasting demolition schemes,the author draws a unanimous conclusion.Under the premise that the structure can be collapsed,it is found that the cut height should not be too high through the comprehensive comparison.The weakened area adjacent to the post support column height has the most significant effect on the recoil distance of the structure.The influence of time delay on the collapse of the structure is more complicated,the appropriate time interval should be based on the specific control variables.