Wind-induced Vibration Of Tall Buildings Research Articles

A novel mechanism - smart morphing façade system - to mitigate wind-induced vibration of tall buildings

Wind-induced vibration plays a significant role in the design of tall buildings, primarily due to serviceability requirements for occupant comfort and structural safety. As a result, several approaches have been developed to address this concern. This paper describes a novel control mechanism, a smart-morphing-façade (Smorphacade) system, using the concept of an aerodynamically modified building façade to mitigate wind-induced vibration of tall buildings. Compared to a fixed-façade system, since a Smorphacade can be dynamically modified in real time based on rapidly-changing wind speed and wind direction during a windstorm, it can be further developed into an active control system. The Smorphacade is comprised of a set of circular ducts embedded in a flat plate and arranged in a matrix formation that is fixed on the original façade but with a gap between the two facades. Each circular-shaped duct is comprised of two parts, a fixed base with alternate open and closed surfaces shaped like a fan-blade and a rotating part similar in shape like the fixed one but placed inside the fixed one and capable of rotation by a protruding fin. By rotating the fin, the porosity of the duct and the fin inclination angle can be simultaneously changed, enabling flow control through the duct. The performance of a Smorphacade system in different configurations was studied using the CAARC standard tall-building model under atmospheric boundary layer wind; its effectiveness in reducing building response was examined by comparing the results of a building with a Smorphacade system to those from one without it. It was found that the effectiveness of the Smorphacade system in reducing the average combined vibration among all three directions (2 transverse and 1 torsional) varied between 16.7 and 18.6%, with a maximum reduction of 32% and 59.7% in across-wind direction and torsional direction, respectively, depending on factors such as Smorphacade configuration, wind speed, and angle of attack.

Investigation on wind-induced aero-elastic effects of tall buildings by wind tunnel test using a bi-axial forced vibration device

Wind-induced vibrations of tall buildings certainly change wind effects on the structures, which is the so-called aero-elastic effect. To date, the approach to identify the aero-elastic effect is still sparse. In this paper, a bi-axial forced vibration device is developed to evaluate the aero-elastic effects of tall buildings via wind tunnel tests. The device can simulate the first-order bi-axial vibration of building models. Furthermore, the surface pressure and the top displacement of the oscillating model can be synchronously measured. The aerodynamic damping ratio and aerodynamic stiffness were identified through analyzing the aero-elastic force acting on the oscillating model. The effects of aero-elastic parameters on wind-induced responses and equivalent static wind loads of a 347 m tall building were examined and analyzed. The results show that for a return period of 100 years, the aerodynamic damping is positive while the aerodynamic stiffness is negative. Aerodynamic stiffness is much smaller than the structural stiffness and therefore it has a negligible effect on natural frequency of the building. Considering the aero-elastic effects, the maximum top displacement and acceleration decrease by approximately 4% and 10% respectively, and meanwhile, the base shear and base moment induced by equivalent static wind loads decrease by approximately 1%. This investigation indicates that wind tunnel test using such kind of bi-axial forced vibration device is an effective approach to identify aero-elastic parameters of tall buildings and even other tall slender structures.

LQG Control of Along-Wind Responses of Tall Building Using Composite Tuned Mass Dampers

A composite tuned mass damper(CTMD) is a vibration control device consisting of an active-passive tuned mass dampers supported on the primary vibrating structure. The performance of CTMD in mitigating wind-induced vibration of tall building is investigated. Optimum parameters of a passive tuned mass damper(PTMD)for minimizing the variance response of the damped primary structure under random loads, with different mass ratio of an active tuned mass damper(ATMD) to a PTMD have been used for the optimum parameters of CTMD. The active control force generated by ATMD actuator was estimated by using linear quadratic Gaussian(LQG) controller, and the fluctuating along-wind load, treated as a stationary random process ,was simulated numerically using the along-wind load spectrum proposed by Solari .Comparing the along-wind rms response of tall building without a CTMD, the CTMD is effective in reducing the response to 40%~45% of the response without the CTMD. Therefore, the CTMD system was effective in reducing wind-induced vibration of tall building.

A combined tuned damper and an optimal design method for wind-induced vibration control for super tall buildings

Summary The wind-induced vibrations of super tall buildings become excessive due to strong wind loads, super building height and high flexibility. Tuned mass dampers (TMDs) and tuned liquid column dampers (TLCDs) have been widely used to control vibrations for actual super tall buildings for decades. To fully use both the economic advantage of the TLCD system and the high efficiency of the TMD system, an innovative supplemental damping system including both TLCD and TMD and called combined tuned damper (CTD), which can substantially decrease the cost of the damper, was proposed to control the wind-induced vibrations of tall buildings. The governing equations are generated for the motion of both the primary structure and the CTD and solved to anticipate the dynamic response of the CTD-structure system. Moreover, an optimal design method of human comfort performance is proposed, in which the life cycle cost of the damper-structure system is considered as the quantitative index of the performance. The life cycle cost includes the initial cost, the maintenance cost and the failure cost. The failure cost can be calculated using the vibration-sensation rate model, which is based on the Japanese code AIJES-V001-2004. Copyright © 2016 John Wiley & Sons, Ltd.

Analysis on Wind-Induced Vibration of Tall Buildings in Hilly Terrain

The responses of tall buildings under wind loads in hilly terrain are remarkably different from that in flat terrain. Wind load codes can’t work efficiently or directly to calculate the wind-induced vibration of tall buildings in hilly terrain. Utilizing some wind tunnel test results of wind field in hilly terrain and pressures on tall buildings, the access to response of tall buildings on hilly terrain were provided. Some effects from hill characteristics to building responses were discussed.

Equivalent mechanical model for tuned liquid damper of complex tank geometry coupled to a 2D structure

Tuned liquid dampers (TLDs) control the wind-induced vibrations of tall buildings using sloshing fluid. TLD tanks of complex geometry may be required in practice due to space limitations; however, their behaviour has not been considered in the literature. This study develops and experimentally validates a model to describe the structure–TLD interaction of a 2D system when the TLD tank geometry is complex. The equations of motion of the structure–TLD system are developed using Lagrange's equation. In general, the 2D structure–TLD interaction must be represented as a coupled four degree of freedom system. The model is validated using new structure–TLD system tests where the structure is subjected to 1D and 2D harmonic and random excitation. Two TLD tanks of complex geometry are considered; the first tank is anti-symmetric about both axes, whereas the second tank is symmetric about both axes. For the anti-symmetric tank, energy transfer between orthogonal structural sway modes and sloshing modes is significant; however, for the symmetric tank, this energy transfer is negligible. Experimental results indicate that the model adequately predicts the structural response; however, the nonlinear behaviour of the fluid response cannot be captured by the linearized model. Copyright © 2013 John Wiley & Sons, Ltd.

Statistical extremes and peak factors in wind-induced vibration of tall buildings

In the structural design of tall buildings, peak factors have been widely used to predict mean extreme responses of tall buildings under wind excitations. Vanmarcke’s peak factor is directly related to an explicit measure of structural reliability against a Gaussian response process. We review the use of this factor for time-variant reliability design by comparing it to the conventional Davenport’s peak factor. Based on the asymptotic theory of statistical extremes, a new closed-form peak factor, the so-called Gamma peak factor, can be obtained for a non-Gaussian resultant response characterized by a Rayleigh distribution process. Using the Gamma peak factor, a combined peak factor method was developed for predicting the expected maximum resultant responses of a building undergoing lateral-torsional vibration. The effects of the standard deviation ratio of two sway components and the inter-component correlation on the evaluation of peak resultant response were also investigated. Utilizing wind tunnel data derived from synchronous multi-pressure measurements, we carried out a wind-induced time history response analysis of the Commonwealth Advisory Aeronautical Research Council (CAARC) standard tall building to validate the applicability of the Gamma peak factor to the prediction of the peak resultant acceleration. Results from the building example indicated that the use of the Gamma peak factor enables accurate predictions to be made of the mean extreme resultant acceleration responses for dynamic serviceability performance design of modern tall buildings.

Increasing Damping Ratios in a Tuned Liquid Damper Using Damping Bars

Wind-induced vibration of tall buildings have been of interest in engineering for a long time. Wind-induced vibration of a tall building can be most effectively controlled by using passive control devices. The tuned liquid damper(TLD) is kind of a passive mechanical damper, which relies on the sloshing liquid in a rigid tank. TLD has been successfully employed in practical mitigation of undesirable structural vibrations because it has several potential advantages: low costs, easy installation in existing structures, and effectiveness even against small-amplitude vibrations. Shaking table experiments were conducted to investigate the characteristics of the shallow water sloshing motion in a rectangular tank. To increase the damping ratio of the rectangular water tank, triangle sticks were installed at the bottom of water tank. This installation increased the damping ratio by amaximum of 40-70%.

Wind-induced vibration of high-rise building with tuned mass damper including soil–structure interaction

In this paper, a mathematical model is developed for predicting wind-induced oscillations of a high-rise building with a tuned mass damper (TMD) when the soil–structure interaction (SSI) is considered. This model is based on time-domain analyses. Numerical examples are used to assess the effectiveness of a TMD for vibration mitigation under wind loads. Results indicate that the proposed model can reasonably reflect soil characteristics. It can more accurately evaluate wind-induced responses of a building with a TMD than fixed-base models. Furthermore, structural oscillations will be overestimated and the effectiveness of TMDs will be underestimated if SSI is neglected. Our findings also confirm that TMDs are beneficial devices in reducing wind-induced vibrations of tall buildings. In particular, they are more effective for the higher soil stiffness. This study will help researchers better understand mechanisms of wind-induced responses for a building with a TMD when SSI is taken into account. It will also improve the understanding of wind-resistant designs for high-rise buildings.

Use of TLD and MTLD for control of wind-induced vibration of tall buildings

Excessive acceleration experienced at the top floors in a building during wind storms affect the serviceability of the building with respect to occupant comfort and discomfort. Tuned liquid damper (TLD) and multiple tuned liquid damper (MTLD), which are passive control devices consisting of a rigid tank filled with liquid, are used to suppress vibration of structures. These TLD and MTLD offer several potential advantages-low costs, easy installation in existing structures and effectiveness even for small-amplitude vibrations. This study carries out a theoretical estimation of the most effective damping ratios that can be achieved by TLD and MTLD. Damping by TLD an MTLD reduced the frequency response of high-rise buildings by approximately 40% in urban and suburban areas.

Development of Active Control System for Wind-induced Vibration of Structures

To reduce wind-induced vibration of tall buildings and bridge towers, tuned mass dampers are often used. These dampers are called “passive type” while the methods which reduce the vibration by controlling the motion of a large mass with an actuator are called “active type”. For these types we have to change or control the structural vibration characteristics themselves, therefore they need very large exciting forces, and the system will become very large for large structures. In this view point, new concepts have just begun to be studied, where the driving forces themselves will be controlled. In this paper, we proposed a new system for reducing the flow-induced vibration of the structures by utilizing fluid excitation force itself. In this system, as we control the direction of the driving forces, this system does not need so large control forces and the system becomes smaller and simpler. We investigated the feasibility of this system when applied to a bridge, a building and evaluated the effectiveness of driving forces by the wind test using a reduced scale model.

Reduced order control for wind‐induced vibrations of tall buildings

AbstractThe design of a structural control system for a tall building may not be easy owing to the large number of degrees of freedom involved. Obviously, it is much easier to design a structural control system for the reduced‐order system than for the full‐order system. Model reduction is thus useful when control systems are implemented in civil engineering structures. A reduced‐order modelling technology for vibration control of wind‐excited tall buildings is presented and its performance is studied. The important issues associated with wind‐induced vibrations, model condensations and reduced‐order control are addressed. Finally, a numerical example, a tall building with an active tuned mass damper or a passive tuned mass damper, is given to show the efficiency of the reduced‐order control technique. Copyright © 2003 John Wiley & Sons, Ltd.

Evaluation of Wind-Induced Vibration Of Tall Buildings and Reliability Analysis: A Case Study

The alongwind, crosswind and torsional components of wind forces are simultaneously measured during a wind tunnel test of a rigid model of a tall building. The three components of wind-induced responses of the tall building are thus estimated and investigated by structural dynamic analysis. A reliability assessment procedure is presented in terms of upcrossing prababilities of wind-induced response and provides a convenient checking procedure for serviceability performance evaluation of tall buildings under stochastic wind loads.

Unified dynamic absorber design formulas for wind-induced vibration control of tall buildings

The objective of this paper is to establish some unified design formulas for various kinds of passive dynamic absorber for wind-induced vibration control of tall buildings. A total of five different passive dynamic absorbers (TMD, TLCD, LCVA, C-TLD and R-TLD) are considered in this study. Firstly, unified equations of motion for the building–absorber system under wind-induced excitation are presented. A set of unified formulas for the optimal properties and the equivalent damping ratios for these five dynamic absorbers are then derived analytically. The Shanghai Central Plaza, which is a thirty-nine-story reinforced-concrete building, is used as an example to demonstrate the procedure and to verify the accuracy of the unified approach. The results show that these unified formulas provide direct performance evaluation and comparison between the five dynamic absorbers for the control of wind-induced vibration of tall buildings. © 1998 John Wiley & Sons, Ltd.

Active vibration control system using a gyro-stabilizer

This paper presents an outline of an active vibration control system using gyro-stabilizers, as well as the results of corroboration testing and an application to control wind-induced vibrations on a 108m tower-like structure. The gyro-stabilizer, which has a flywheel with a single gimbal, generates moments to control wind-induced vibrations of tall buildings with a predominant bending mode of deformation. Records of forced vibration tests confirmed that the control gain was smoothly changed in accordance with the response of the structure, resulting in an increase of the damping ratio of the structure from 0.25% to 1.6%. The effectiveness of the gyro-stabilizers was also corroborated by the response records observed in an application of the system to wind-induced vibrations. These records show that the acceleration response with control was reduced to less than a half of the response without control.

Wind-Induced Vibrations of Tall Buildings Obtained by Full Scale Measurements

Wind-Induced Vibrations of Tall Buildings Obtained by Full Scale Measurements

Response analyses on along-wind and across-wind vibrations of tall buildings in time domain

This study discusses the application of a numerical simulation technique to estimate wind-induced vibrations of tall buildings. We simulated fluctuating wind forces acting on a tall building in along-wind and across-wind directions using the technique which was developed by Tamura et al.(1988). The power spectrum of the fluctuating wind force in along wind direction is expressed as the product of the power spectrum of the fluctuating windspeed and the aerodynamic admittance. While, in the case of the across-wind direction, the power spectrum of the lift force is approximated by a mathematical expression based on wind tunnel data. These techniques are proceeded to use for analyses of the along-wind and across-wind vibrations of tall buildings, estimating displacement and acceleration. Further analyses of the response of a building installed with a Tuned Mass Damper(TMD) are also carried out to examine its efficiency.

Tuned mass damper using multistage rubber bearing for vibration control of tall buildings. (1st report, Fundamental study of the vibration characteristics).

For control of wind-induced vibration of tall buildings having long natural periods of 6s, or so, tuned mass dampers must respond to the floor motions with small accelerations. Therefore the tuned mass dampers must have mechanisms/structures which enable them to oscillate with the least friction. To satisfy this requirement, a tuned mass damper using multistage rubber bearings was developed, in which the moving mass was supported by the rubber bearings and could move with very small friction. To investigate dynamic characteristics of the mass damper, excitation tests were carried out for a scale model of the mass damper. The model was designed to have an effective mass of 5000kg with a horizontal natural period of 2.0s. In the model a single multistage rubber bearing was used to support the moving mass, which consisted of 12 stages (each stage comprising 4 rubber bearing elements and 8 oil dampers) stacked up with 11 stabilizing plates between the stages. Through the tests, it was revealed that the mass damper had some nonlinear vibration characteristics. Analytical models to simulate the nonlinear vibration were developed.