Analysis On Seismic Performance Of Frame-type Underground Construction

Due to increasing severity of limited land resources in contemporary cities, utilityof underground space is believed to be one of best approaches to meet a greater volumeof construction in the coming decades. Quite often, underground structure was moreseismic-resistant than its above-ground counterparts, thus the aseismic properties of thefomer hadn’t been well explored until the great earthquake in Nagoya, Japan,1995.Serious damage upon underground structure was identified, which in return, broughtdramatical change to traditional opinion that seismic design was not a necessary part forthe design of underground structure. Instead engineers began to realise seismic damagecan be a potential threat to underground structure, and, such damage might be difficultto be removed. In China, the importance of seismic design on underground structure ishighlighted in a newly added Chapter14in Code for Seismic Design of Buildings(GB50011-2010). However, compared to the rapid development of undergroundstructure, the theory of seismic design is lagged greatly.Based on theoretical analysis and numerical simulation, this eassy aims to focuson frame-type underground structure design. Differce between the properties ofundeground and above-ground structure will be listed and compared in followingways.Firstly the author establish a3D finite element mechanical model of frame-typeunderground structure, through which the artificial boundary conditions，geostressbalance and different materials of damping will be tested. Aftermath, a series ofparameters including different intensity of earquake, different rock type and verticalearthquake input will be applied to the model to analyse the seismic behaviors ofunderground structure in differed conditions.The main conclusions of this article are as follows:①With the interacting influence of soil and structure, frame-type undergroundstructure’s drift is smaller than ground structure’s, the drift of base layer is even bigger,so the base layer is the weak part.②For different types of surrounding rocks, with the surrounding rock softened, theweaker it constrains on the structure, the greater the deformation between the structureof the layer is; But the change of internal force and deformation in the structure isnot consistent，just by deformation of the structure to deduce the stress is notreasonable. ③Vertical earthquake motion has a significant influence on the column of theFrame underground structure. In the high peak value of vertacai earthquake motion,thedamages easy happen in the bottom column-end of frame underground structure,but inthe Top-level column-end,for the significant change on the dimension and Direction ofthe column axial force,it will form the weak parts.④Only under the action of horizontal earthquake,it mainly appears the “beamhinge” in the Frame underground structure;When under the combined action ofHorizontal and vertical earthquake, The “column hinge”will advance appears and bemore common,and Easier form the beams mixed hinge.For the reasons,one is thesignificant change of the column Axial force.