Simulation Analysis On Collapse Of Reinforced Concrete Frame Structure Under Mega Earthquake

Reinforced concrete frame structure is one of the most common structure forms inChina. Research of RC frame structure has been relatively mature under minor, middle,or major earthquake. However, research on collapse mode and mechanism of RC framestructure has been insufficient under mega earthquake. And study on escape space–refuge unit is still in preliminary stage. Therefore, it is necessary to have analoguesimulation for the collapse behavior of frame structure under mega earthquake, whichdetermines influencing factors and studies the mechanism of the collapse, finally putsforward reasonable arrangement mode of refuge unit.On the basis of existing achievements of the collapse of studies, multiple sets offrame structure model was established by using ANSYS/LS-DYNA analysis software inthis paper. In which influence of intensity of ground motion, structural layers, andstorey height of bottom layer on frame structure collapsed under mega earthquake,analyzed the collapse mechanism, contrasted the response of the frame structures whichwere designed according to the old or the new seismic code, and put forward escapespace for personnel--refuge unit, and draw the following conclusions:①The collapse of frame structure can be successfully simulated under megaearthquake by using ANSYS/LS-DYNA software, in which material models andparameters have been reasonable selected, as well as material failure criteria andcollision contact manner have been accurately defined. Compared with the earthquakedamage rule, simulation results of the collapse process of structure model are basicallyidentical.②Influence of intensity of ground motion, structural layers, and storey height ofbottom layer on collapse of frame structure is great under mega earthquake response.With the greater of intensity of ground motion and more layers, frame structure will becollapsed the easier or the earlier. Changes in storey height of bottom layer will affectthe vertical stiffness distribution of frame structure. The underlying stiffness which istoo large or too small will affect energy consumption of frame structure, finallygenerating an adverse effect on the structure to resist mega earthquake action.Simultaneously, specification on elastoplastic interlayer displacement angle limitation1/50under large earthquake, to some extent, can control the collapse of frame structureunder mega earthquake. ③Relative to the old code (GB50011-2001), the frame structure is designed inaccordance with the new cold (GB50011-2010), in which moment magnification andshear-enlarged coefficient of the columns are obviously increased. So the bearingcapacity and ductility of frame structure are improved significantly. The collapseresistance of the structure improves obviously, and begins to collapse significantly laterthan the frame structure which is designed according to the old code.④Refuge unit installed in the reinforced concrete frame structure is effective. Therefuge unit which is arranged around concrete column filled steel tubular (or sectionsteel) has high bearing capacity and good ductility. Even though non-refuge units haveoccurred severe plastic deformation and partially lose bearing capacity under megaearthquake, refuge unit can still continue to deformation and load, not collapsed.Therefore refuge unit with concrete column filled steel tube (or section steel) isreasonable.