Dynamic Response And Sliding Isolation Of Structures On The Ground Subjected To Underground Explosion Waves

A fierce explosion occurring in an underground tunnel of city usually causes severedamage to the tunnel lining, the surrounding soil and even some structures on the groundadjacent to the tunnel. In order to discover the laws for the dynamic responses ofdifferent types of structures to the underground explosion waves from the accident andthen to develop some shock absorber or isolator of those structures and evaluate theireffects, a systematical study on the dynamic responses and the sliding-isolation effects ofthe three types of structures, consisting of the multistory building, the long-spanroof-truss structure and the continuous-girder bridge, under the impact of theunderground explosion waves is performed in this dissertation, and the primaryinnovative work and achievements are as follows.(1) Some different kinds of numerical methods are introduced to establish variouscoupling models of systems, including the underground tunnel, semi-infinite soil and thethree types of structures whether their sliding isolation equipment is installed or not,using sub-structure theory. According to the proposed simplified model of overpressureon the tunnel wall and the von-Mises' and the Mohr-Coulomb's yielding principlescorresponding to the tunnel and the soil around respectively, the elaso-plastic dynamicresponses of various systems to the explosion inside the tunnel are numerically analyzedby means of the equivalent-load method in the Newmark increment calculation. Incomparison with the results of the Lysmer viscous boundary method and the modifiedLysmer viscous boundary method, the validity of the methods proposed in thedissertation is proved.(2) In respect of the sliding base-isolation analyses of the multistory building and thelong-span roof-truss structure and the friction pendulum isolation analyses of thecontinuous-girder bridge, the mechanical models of various isolation installations arebuilt, and a number of the modified continuous friction models with the compressiveforce of the sliding interface and the sliding velocity relative regarded as the independentvariables are proposed. This not only avoids some disadvantages of the traditionalCoulomb friction model, like tracing momentarily the phases of the meshing and thesliding and the boundaries between them and resulting easily in remarkable accumulatederrors, but also makes the process of determining the friction simplified greatly.(3) With a method suggested in the dissertation to determine the plastic region of element,the law of extending of the plastic region in the tunnel and the soil around on account ofthe explosion happening in the tunnel is investigated. In addition, the varying trends ofthe peak displacements, the peak velocities and the peak accelerations at the surfacepoints of the free-field are analyzed, and the travelling-wave effects and the attenuationcharacteristics of the underground explosion waves propagating along the earth's surfaceare testified at the same time. As for the complicated computation about the dynamicresponses of the three types of structures to the underground explosion wavesconsidering the soil-structure interaction, the independent work of every sliding isolationinstallation and the traveling-wave effect of the blast waves all together (the last twofactors are mainly related to the long-span roof-truss structures and the continuous-girderbridge), the models and solutions offered in the dissertation can be used to naturally andbetter deal with it. For the continuous-girder bridge, the related models and solutions canalso naturally consider both the influence of the concave surface of the earth on thetraveling-wave effect of the blast waves and the scatter problem of the blast waves on theconcave surface.(4) Some comparative analyses on the dynamic responses of the multistory building andthe long-span roof-truss structure, considering no isolation and the sliding base-isolation,to the underground explosion waves are executed usi...