Study On Nonlinear Wind-induced Response Of Tall Building Isolated By Friction-Pendulum Bearing

The earthquake and wind disasters occur frequently on the world.There are multi-hazard overlapping areas,such as Hainan,Fujian and Taiwan of China which not only experience high-intensity earthquake,but also often suffer from the strong wind.As one of the effective measures to reduce earthquake disasters,isolation technology has been popularized in high-intensity earthquake areas in recent years.In general,the seismic energy is concentrated in high-frequency band.The isolated buildings utilize the isolation system to reduce the fundamental frequency and increase the damping to decrease the seismic response.However,wind load consists of low-frequency components.According to the current elastic wind vibration design for the isolated tall building,the reduction of the fundamental frequency as result of the isolation system makes the wind load more inclined to be a dominant load.If the isolation layer is permitted to enter the nonlinear state,the increased damping of the isolation layer is effective to reduce the wind-induced response.To seek this relaxed structural design,it is particularly important to study the nonlinear wind-induced response of isolated high-rise buildings.As the main component of the isolation system,the widely-used isolation bearings include elastomeric bearing and friction pendulum bearing(FPB).Different from elastomeric bearings,FPB achieves energy dissipation through the friction mechanism between slider and sliding plate.The curved sliding plate converts kinetic energy and gravitational potential energy,and provids re-centering force.In recent years,it has been found that FPB has higher bearing capacity,more stable performance and good re-centering capacity.For FPB isolated tall buildings,the low friction coefficient reduces the threshold of yield force,and generally achieves excellent isolation effect.However,the isolation layer is more prone to sliding when the building encounters strong wind,resulting in complex nonlinear wind-induced vibration.Therefore,the wind-induced response characteristics FPB base-isolated tall buildings subjected to separate alongwind and crosswind are studied firstly.The response history analysis and statistical linearization method to computed wind-induced response are compared.Considering the bidirectional dependence of frictional force or the possible eccentricity of upper structure,the dynamic coupling of FPB base-isolated tall buildings under three-dimensional wind load is further investigated.Furthermore,the time-domain analysis framework and statistical linearization method for the wind-induced vibration of FPB base-isolated tall buildings are extended to that of FPB inter-story isolated tall building.An enhanced simplified model for dynamic response analysis of inter-story isolated tall buildings is proposed.Finally,the wind-induced coupled response of the FPB inter-story isolated tall building to synchronous three-dimensional wind load is also studied.The main contents of this dissertation are as follows:(1)Uncoupled along-and crosswind responses of FPB base-isolation tall buildingA theoretical framework involving the time-domain analysis and statistical linearization method to determine uncoupled along-and crosswind response of FPB base-isolated tall building is presented.Taking a tall building isolated by FPB as an example,the along-and crosswind response characteristics of building are discussed,and different methods of response calculation are compared.The response ratios of base-isolated buildings over fixed-base buildings under different wind speeds are analyzed.The effects of radius,friction coefficient and shape of sliding plate on wind-induced response of buildings are investigated.(2)Coupled dynamic analysis of FPB base-isolated tall buildings under three-dimensional wind loadThe coupled dynamic analysis framework of FPB base-isolated tall buildings under3 D wind field is established firstly,where the biaxial Bouc-Wen model and the velocity-dependent friction coefficient are used to express the three-component force vector of the isolation layer.Taking FPB building with rectangular section as an example,the synchronous 3D wind loading on the building is obtained from the pressure measurement in a wind tunnel.The structural responses,including building top displacement and acceleration,base displacement,and displacement of individual bearing,are compared under the uniaxial,biaxial and triaxial wind loads.The distribution of friction-induced dissipation energy in vibrational direction is quantified.Furthermore,the influences of the wind direction,stiffness eccentricity and torsional stiffness of upper building on structural response are investigated,and the wind-induced torsional coupling effect of the building is revealed.(3)Uncoupled wind-induced response of FPB inter-story isolated tall buildingAs a more general version of FPB base-isolated tall building,the time-domain analysis framework of wind-induced dynamic response of FPB inter-story isolated tall building is built.An approach to select enhanced simplified model of inter-story isolated tall buildings is proposed.Considering the independence of the lower and upper structures,two structural design schemes of inter-story isolated tall building are provided,their dynamic characteristics are analyzed and crosswind responses are compared.In addition,the standard deviation(STD)and maximum of crosswind response of building are estimated by Gaussian statistical linearization method.(4)Coupled dynamic analysis of FPB inter-story isolated tall buildings under three-dimensional wind loadThe coupled dynamic equations of inter-story isolated tall buildings under synchronous three-dimensional wind loads are derived.The method to select simplified model of inter-story isolated building in one-dimensional motion is extended to three-dimensional motion.On the condition of stiffness eccentricity,the influences of structural eccentricity from lower and/or upper building on the wind-induced vibration of the whole building are investigated.The three-dimensional wind-induced response characteristics of variable frequency friction-pendulum bearings are explored and their wind-resistant performances are compared.