Study On Shock Isolation And Reduction Of Spatial Reticulated Shell Structure On The Ground Subjected To An Underground In-tunnel Explosion

Because of their complicated shape, the large number of nodes and rods, and concentrated distribution of natural vibration frequency, the studies on shock isolation and reduction of spatial reticulated shell structures, which are widely applied structures, are limited and mainly focused on those anti-seismic and anti-wind aspects. In recent years, accidental explosions in underground tunnels of cities take place frequently, causing not only the loss of lives and belongings but also severe damage to the tunnel lining and even some structures on the ground adjacent to the tunnel. In order to discuss the measures and effects of shock isolation and reduction of spatial reticulated shell structure on the ground subjected to an underground in-tunnel explosion, this paper analyzes the measures of shock isolation and reduction of spatial reticulated shell structure on the ground subjected to the underground in-tunnel explosion and evaluates their effects systematically. The main contents and achievements are as follows:(1) By using LS-DYNA software, the author establishes various coupling models of systems, including the underground tunnel, semi-infinite soil and the two types of structures whether their base isolation or reduction equipment is installed or not. The explosive-air-tunnel coupling model is established with the LS-DYNA software and the overpressure on the inner surface of tunnel is obtained. The material parameter of Drucker-Prager model to simulate soil, HJC model to simulate concrete subjective to large strains, high strain rates, and high pressures, and plastic kinematic material model to simulate steel are presented. Rubber and viscous damper, which constitute the shock isolation and reduction technology of this paper, are discussed. The laminated rubber bearings and linear viscous dampers are usually widely applied in engineering, and the Blatz-Ko rubber model and linear viscous damper model are adopted to simulate the laminated rubber bearings and viscous damper.(2) By using the way offered in the present dissertation, shock isolation and reduction of double-layer cylindrical reticulated shell subjected to underground explosion waves is studied through methods like setting rubber bearings and replacing viscous damper. It is found that the longitudinally disposed tunnels along reticulated shells are the most unfavorable if the distance between them is given. The corresponding peak values like the stress of rods, the relative displacement of nodes between rods, and the acceleration of the nodes of double-layer cylindrical reticulated shell could be reduced significantly by setting rubber bearings and replacing viscous damper. Meanwhile, the method of setting rubber bearings could also prolong the oscillation period of the structure. When tunnels are disposed longitudinally along reticulated shells, method of replacing upper chords should be adopted while method of replacing longitudinal rods should be used when tunnels are disposed transversely along reticulated shells.(3) The numeral analysis of shock isolation and reduction of single-layer spherical lattice shell through setting rubber bearings and replacing viscous damper is executed by using the method given in this paper. It is found that by setting rubber bearings and replacing viscous damper, not only could the peaks tress of the rode pieces of single-layer spherical lattice shell and the acceleration peak value of nodes be decreased drastically, but also the oscillation period of the structure could also be prolonged significantly. And the method of replacing sway rods should be adopted.The analysis results of the paper provide references for the design and application on shock isolation and reduction of those two types of reticulated shell structures subjected to underground explosion waves.