Study On Failure Mode And Explosion-Proof Method For K8-type Steel Reticulated Shell Under Internal Explosion

Single-layer K8-type spherical steel reticulated shells are often concerned by the terrorists as a large public building.In the context of today's terrorist bombings and factory explosions,the use of engineering means to protect the K8 reticulated shell has become the consensus of the majority of scholars.In this paper,the data of internal explosion experiment is used to verify the accuracy of LS-DYNA numerical simulation.Based on this,the numerical model of K8 spherical shell is established by using LS-DYNA.In the event of an internal explosion of K8,the shock wave overpressure,structural dynamic response,venting threshold and the failure mode,the collapse after the explosion are systematically studied,and the corresponding conclusions and explosion proof suggestions are obtained.The main contents include:(1)The difference between the K6 spherical reticulated shell explosion test data and the corresponding LS-DYNA numerical simulation data is compared and analyzed.The results show that: 1)The peak value of shock wave and the peak value of rod strain are similiar in experiment and numerical simulation.2)The experimental and numerical simulations all show that the strain value of the radial rod in dome and the annular rod in border are larger than others.3)reasonable wall openings on the reticulated shell has a certain release to shock wave overpressure,nevertheless different parts will have different effects.(2)Based on the experimental provement of LS-DYNA numerical simulation,the finite element model of K8-type spherical reticulated shell was established by the same modeling method.The influence of TNT explosive and the tensile strength(EA)of connecting member on the damage mode of envelope and main structure were calculated and analyzed.The damage pattern of the envelope and the main structure is classified.And the explosion threshold value ? Pf of the structure under different failure modes is obtained by extracting the shock wave pressure value on the surface of the envelope.The The results show that when the amount of TNT is constant,the failure mode of the envelope is serious with the increase of EA,but the damage pattern will not change after exceeding a certain value.While EA=14.6×107N/m,theplastic strain value of the bar is the smallest.(3)The numerical simulation of the K8 spherical reticulated shell is divided into three stages: before explosion,explosion and after explosion.The LS-DYNA Full Restart function is used to simulate the three stages respectively,and the main structure after the explosion is loaded,The results are summarized as follows: 1)the less restraint point is the more likely to collapse the reticulated shell is.2)The larger the eccentricity of the explosive is,the greater the dynamic response of the reticulated shell is.The reticulated shell collapses from two symmetrical outer ring bars when the eccentricity is 15 m.With the increase of TNT equivalence,the greater the damage is caused on K8 spherical reticulated shell,and the more likely it is to collapse.3)The explosion-proof method research system based on the three-stage analysis of K8-type spherical reticulated shells is established,which can provide explosion-proof method and research ideas for such internal explosion problems.