Research On The 3D-pounding Behaviours Of Adjacent Buildings

Out of phase vibration is observed between adjacent buildings which have different dynamic characteristics under seismic load,and pounding is observed when seismic joint can't meet the need of relative movement of adjacent buildings.According to many earthquake surveys,pounding is one of the main reasons that lead to collapse of buildings.Actually,the average building is eccentric arranged(mass eccentric,stiffness eccentric,etc.),such adjacent buildings tend to need larger seismic joint to avoid pounding,yet most of the models used in research of pounding problems are based on plane assumption so far.So the actual responses of adjacent buildings may exceed the expect of research results based on plain models.Besides,the main transmitting orientation of earthquake wave is along the principal axis,including the unidirectional input and bidirectional input along the principal axises of the structure,in the area of researching the pounding behaviours of adjacent buildings.However,this is just a special case.For pounding behaviours research using 3D model,the influence of input direction of earthquake acceleration records on pounding need to be clarified.Consequently,the aim of this paper is to investigate the 3D-pounding behaviors of adjacent buildings which have eccentric arranged in mass and the influence of input direction of earthquake acceleration records on pounding.Hence,the following researches are carried on:(1)The typical analytical methods used in dynamic pounding problem are summarized and their advantages and drawbacks are discussed.Based on energy dissipation equivalent,a simplified Hertz model is introduced.With the help of Perform-3D software,finite element model for 3D-pounding of adjacent buildings of single storey concrete frame,attached in building corners of adjacent joints with contact elements which is formed by nonlinear series bar group based on simplified Hertz model and gap-mechanism,is developed.(2)Four adjacent building models with different eccentric arrangement were selected.The characteristics of pounding and the dynamic response rules of adjacent buildings eccentric arranged are discussed.The research shows that pounding intensity of structure corner in flexible edge of eccentric structure is larger than that of rigid edge,and obvious torsion is observed in symmetric structure because of corner pounding.Besides,The column top displacement amplification effect of eccentric pounding is partially lager than that of symmetric pounding.(3)The influence of joint width on the eccentric pounding response is discussed.The research shows that the pounding intensity peak decreases with the increase of the joint width of adjacent buildings,and eccentric arrangement of adjacent building may further amplify the pounding force peak on the base of symmetric one.(4)The influence of period ratio of adjacent buildings on the eccentric pounding response is discussed.The research shows that the maximum value of the peak values of pounding intensity.occurs at the position of the period ratio TB/TA=0.6,and the increasing influence of pounding on the displacement peak of the softer side of adjacent buildings is significantly increased,the maximum value of which occurs at the position of the period ratio TB/TA=0.6.(5)Four near-field seismic accelerograms are matched with the response spectrum determined by the Chinese code to generate four artificial accelerograms.Three types of single layer concrete frame structures which have different direction of mass eccentricity are modeled.The pounding response of adjacent buildings under variable input direction of seismic accelerograms is studied.The research shows that the pounding force and the structural displacement of the adjacent buildings are decreased with the increase of the input angle of the seismic wave,and there are obvious differences in the response of adjacent buildings with different mass eccentricity.