Load Distribution And Dynamic Response Of Beam And Slab Of Underground Structure Under Internal Explosion

Underground structures is closed and when an underground structure filled with alot of people was subjected to internal explosion and could not bear the blast loadmany people in it would lose lives or be wounded. So it is necessary to do sometheoretical research on internal explosion which happens in underground structures soas to find ways to improve the structures’ resistance to internal blast loads. This paperwill study the blast load distribution and the dynamic response of the beam and slabof underground structures, which will provide some guidance for research onunderground structures’ anti-internal-explosion capability.The main works and achievements of this paper are as follows.(1) In this paper, taking a method of reinforcement and concrete separatelymodeling the numerical models of one-storey reinforced concrete undergroundstructures were built up, the material models and equations of state were chosen formaterials which used in the numerical models, the two-stage and three-stagenumerical simulation methods which were used in this paper were introduced, theviscoelastic boundary of the soil is determined and the reliability of the softwareLS-DYNA in studying internal blast loads was verified.(2) Based on the numerical simulation analytical method this paper studied theinternal blast load distribution on the frame beam surface of the underground structureunder different covering soil thicknesses. It is found that for underground structureswhich are not buried deeply the soil nearly has no effect on the blast loads and blastload distribution on the surface of the members.(3) This paper studied the changes of the internal blast load distribution on thesurface of the beam and the slab as the explosive location and the explosive weightchanged. It can be concluded from this study that when the detonation point is belowthe beam or the slab middle the overpressure peak and the impulse on the projectionpoint and the beam or slab end are usually larger than other points, in the area aroundthe beam or slab end the impulse changes heavily and the impulse on the beam or slabsurface increases with the increment of the distance between the detonation point andthe beam or slab surface. When the explosive height is fixed and the horizontal location of the explosive changes and there is certain distance between the detonationpoint and the column or the wall the overpressure peak will not change as theexplosive moves in horizontal direction. When the explosive weight varies under littleexplosive weight the overpressure peak and the impulse in the areas except that nearthe beam and slab end distribute uniformly and the overpressure peak and the impulseenlarge with the increment of the explosive weight.(4) Taking covering soil thickness and the soil shear modulus into account, thispaper studied the soil effect on the dynamic response of the beam and slab of theunderground structures. It is found that covering soil with certain thickness isbeneficial for the anti-internal-explosion of the beam or slab of the structure, however,if the internal blast load is enough large and the beam or the slab comes into theplastic stage there is probably a disadvantage under thicker covering soil. It is alsoindicated that when the shear modulus is larger the deformation and the damage of thebeam or the slab under internal blast loads is less and the anti-internal-explosioncapability of the beam or the slab will improved. After the beam or the slab come intothe plastic stage under the internal blast load, the plastic hinge will firstly appear atthe beam or the slab end and the concrete and the reinforcement at or near the beam orthe slab end will have very large stress in a short time after the internal explosiontakes place.(5) According to the fundamental thought of the equal time centroid simplifiedmethod, the partition and no partition equal time centroid methods used for thesimplification of the internal balst loads on the reinforced concrete slab were putforward and the rationality of the two methods are proved by the numerical simulationresults.