Research On Seismic Behavior Of Isolation Rubber Staircases And Frame Structures

Staircases are the important passage for self-and mutual rescue of the public during the Earthquake.If they damage seriously,result in Interruption even plugging of the passage.Consequence will be incredibly bad.In order to releasing brace effect of the stairway slabs,in connection with contents of 11G101-2,propose the measure of adding sliding supports at the lower of the stairway slabs.But the sliding supports may lead to large hidden trouble.Therefore,propose the measure of adding seismic isolation rubber supports at the lower of the stairway slabs in this paper.The applying of the seismic isolation rubber supports for a six-story reinforced concrete substructure was built and analyzed using ETABS.Taking RC staircase frame unit added two kinds of supports at the end of the stairway as an object.The shaking table test of a 1/3 scaled model structure was conducted to research the seismic performance.Main contents and achievements of the dissertation are as follows:(1)To examine the effect of adding isolation and collapse preventing bearings for the stair of concrete frame structure,four frame modes with four different staircases which include sliding bearings and isolation and collapse preventing bearings,were built using ETABS.The seismic performance of different details at end of stair plate were analyzed and compared.The results showed that the period,mode,seismic performance,story drift and the force of ladder beams,columns,beams and columns of the frame structure change slightly,after adding isolation and collapse preventing bearings,compared to the model which ignore the staircase effect.This suggests that the isolation bearing can effectively release the brace effect of stair plate.Compared to the model added sliding bearings,the sliding displacement along the direction of horizontal ground motion of the model with isolation and collapse preventing bearings,is almost the same.And the vertical displacement of the stair plate was reduced.(2)To study influence of isolation and collapse prevention bearings at end of stair plate and location of the stairs on the seismic performance of reinforced concrete frame structures,three groups and six models including isolation collapse prevention supports were built by ETABS.The effect of frame structures with isolation and collapse prevention bearings and stairwell location on the vibration,internal force,and failure mechanism were analyzed by modal analysis,response spectrum analysis and Pushover analysis.The calculation results show that the location of stairwell has little impact on torsion of frame structures after adding isolation and collapse prevention bearings,and the vibration in the two major axis direction of frame structure is similar,the internal force of stair columns is significantly reduced.When the layout of the stairwells is in the side span,the internal force of stair columns is stronger when the frame is subjected to an earthquake in the direction of perpendicular to the ladder.The frame beams have improved the structural seismic performance by dissipating the earthquake energy.The overall stability of the stairs can be guaranteed with the isolation and collapse prevention bearings,and the failure of stairs is delayed during a major earthquake.(3)In order to verify the influence of seismic isolation rubber supports as well as ploytetrafluoroethene plate sliding supports at the lower of the stairway slabs on the seismic performance of cate-in-place reinforced concrete(RC)slab-stairs,taking RC staircase frame unit as an object,the shaking table test of a 1/3 scaled model structure was conducted to observe the failure process and failure mechanism,and to analyze the natural vibration frequency,acceleration response and displacement response by inputting motions of different intensities.Experimental results indicates that staircase unit with seismic isolation rubber supports at the lower of the stairway slabs had excellent seismic performance and failure concentrated in main structure under rare seismic,which released brace effect of the stairway slabs effectively and realized that substructure failed seriously later than main structure.When ploytetrafluoroethene plate sliding support was used at the lower of the stairway slabs,severe vertical cock and horizontal sways occurred in the resonance destruction test.However,when seismic isolation rubber support was used at the lower of the stairway slabs,vertical acceleration of staircase slabs decreased,no sway occurred in the resonance destruction test.The seismic rubber supports in two types of stairway columns could filter out highfrequency earthquake wave,but double frequency spectrum phenomenon was obvious.For sub-structure staircases supported by three stairway columns and one frame column,seismic rubber supports can greatly reduce the peak value of frequency spectrum,and the escaping probability would be increased.For sub-structure staircases supported by four stairway columns,both types of the supports would slightly increase the peak value of frequency spectrum.The damage degree of sub-structure staircases equipped with two supports is similar.The stairway slabs experienced small axial force when seismic isolation rubber supports was equipped at the end of them,thus the brace effects should be neglected.