Comparative Study On Wind-induced Vibration Control Efficiency Of High-rise Buildings With Various TLD Systems

Tuned liquid damper is a passive energy absorber,which has been successfully used in vibration control device for tall buildings.Usually it is firmly attached to the top of building by a water tank.Under the action of wind loading and earthquake effect,the vibrating building causes the water to slosh in the water tank.If the frequency of the water sloshing is tuned to match the natural frequency of the first vibration mode of the main structure,the inertial force of liquid sloshing is transmitted to the structure.The direction of the inertial force is opposite to the direction of building motion,therefore it can reduce the vibration response of the structure.This means that the additional damping caused by the water sloshing is supplied to the structure.In recent decades,the response of structure with Tuned Liquid Damper(TLD)system has been extensively studied under wind loading actions.One way to study the structural behavior of TLD system is to replace TLD with equivalent Tuned Mass Damper(TMD).With the obtained equivalent mass,stiffness and damping ratio of the equivalent TMD model,the dynamic behavior of TLD can easily and reasonably described.These parameters of the equivalent TMD model are derived from Navier-Stokes equations and shallow water wave theory.Meanwhile the inherent damping of TLD can be increased by adding internal obstacles such as screens to improve thevibration control efficiency of TLD.In this paper,slat screens are adopted as they have many practical advantages.The main contents of this thesis are as follows:In order to study the efficiency of wind-induced vibration control of various TLD systems in tall buildings,a 432 m tall building(Guangzhou West Tower)is selected as an example in this paper.The time histories of the external wind loading with different years in return period were obtained from the wind tunnel test on the scaled model of this building,and various types of conventional TLD systems are installed atop of the building.Firstly,the TLD model is simplified by Housner's lumped mass model.The TLD system is modeled as a Mass-Spring-Damper system.Secondly,the deep-water wave theory was adopted to deduce the formula of dynamic water pressure in rectangular deep-water TLD under dynamic base excitation.The motion equation of structure-TLD system is obtained for the above two TLD models and the solutions of wind-induced response of the investigated building under wind loading were carried out.The vibration control effects of these two TLD models on wind-induced response of the tall building were compared.When the conventional TLD system is subjected to large-amplitude base excitation,nonlinear effect can be caused by the intensive water sloshing and large displacement.The Nonlinear Stiffness and Damping(NSD)parameters of equivalent TMD model was proposed by Yu to simulate the structural nonlinear behavior of TLD system.This type of TLD is also adopted to model the TLD system atop of Guangzhou West Tower to evaluate the wind-induced response of this tall building with nonlinear TLD model.The analyzed results for this case are compared with numerical analysis results of wind-induced responses of this tall building with TLD system described by the lumped mass model and deep-water wave theory method.For the TLD system with the inherent slat screens in the tank,the equivalent linear and non-linear TMD model were proposed by Tait to model the structural behavior of this type of TLD by the principle of equivalent energy dissipation.The empirical formula for equivalent mass,stiffness and damping ratio are obtained for the equivalent linear TMD model.And the variation of vibration mass,stiffness and damping ratio with the increased amplitude in based excitation were also deduced for the equivalent non-linear model due tolarge amplitude in water sloshing.The wind-induced response of the investigated tall building with these two types of TLD system.The numerical analyzed results for these two cases were also compared with the estimated results for the tall building with the same TLD system but non-inherent screens arranged.The compared results show that inherent screens in TLD system could effectively enhance its energy dissipation effect,and the TLD system with inherent screens could have more efficiency in wind vibration control than the traditional TLD system.Finally four same TLD systems with the inherent slat screens were assumed to be fixed atop Guangzhou West Tower,the formula for the equivalent mass,stiffness and damping ratio of the equivalent non-linear TMD model are also obtained by Tait's method.The efficiency of wind vibration control of the tall building with Multiple TLDs(MTLD)was compared with those numerical analyzed results from the single TLD with screens and conventional TLD model.The validity of wind-induced vibration control efficiency of MTLDs with the inherent slat screens is verified.