Wind-induced Response Of Tall Buildings Research Articles

Study on the Peak Factor of the Wind-Induced Response of Super-High-Rise Buildings

The wind-induced responses of tall buildings are stochastic processes, and the peak factor is an important parameter to evaluate the extreme value of the wind-induced response in wind-resistant design. The existing research on the peak factor mainly focuses on the wind pressure on the building surface, but rarely concerns the wind-induced response peak factor of the structures. In view of this, the peak factor of the wind-induced response of super-high-rise buildings was studied in this paper. Firstly, a series of wind tunnel tests of the multi-degree-of-freedom aero-elastic models (MDOF) were carried out, wherein the along-wind and cross-wind responses were measured. Thereafter, the peak factor of wind-induced response was calculated using the peak factor method, classical extreme value theory, and the improved peak factor method. It was found that the peak factor calculated by the improved peak factor method is in good agreement with classical extreme value theory, which indicates that the improved peak factor method is applicable to calculate the peak factor of the wind-induced response of high-rise buildings. The results calculated using the improved peak factor method show that the peak factor of cross-wind response varies significantly with the wind speed, varying from about 2.5 to 5.5. The peak factor of cross-wind response first increases and then decreases with the increase in the wind speed, reaches the minimum near the critical wind speed of vortex-induced vibration (VIV), and increases again when the wind speed is larger than the VIV wind speed. Finally, an empirical formula for the cross-wind response peak factor was proposed as a function of the reduced wind speed, aspect ratio, and damping ratio of the structure.

Aerodynamic loads correction method based on wavelet packet transform in high-frequency force balance tests

High-frequency force balance (HFFB) technique is a commonly used method for acquiring wind-induced response of tall buildings in wind tunnel tests. However, the resonance buffeting of the balance-model system (BMS) results in the distortion of measured aerodynamic loads. When the signal distortion is complicated due to additional vibration modes and noise interference, the existing methods fail to obtain correction results. Thus, a new correction method based on wavelet packet transform (WPT) is proposed in this paper to address the issue. The distorted signals are decomposed by WPT, and the relationship between wavelet packet coefficients and power spectral density (PSD) estimation is established. Then, the reference line that conforms to the aerodynamic attenuation characteristics is extracted by a single-degree-of-freedom (SDOF) correction method combined with a parameter identification method. Subsequently, the wavelet packet coefficients of SDOF correction results are adjusted according to the reference line. Finally, the time history of the aerodynamic load after correction is reconstructed by inverse WPT (IWPT). The proposed method is validated by a numerical example and applied to a HFFB test. Compared with the existing methods, the proposed method can address more complex distortion scenes and extend the correction frequency range to the Nyquist frequency.

Factors Impacting the Intensity of Vortex Shedding on High-Rise Buildings

The wind-induced response of tall buildings is usually dominated by dynamic across-wind vortex shedding. The intensity of vortex shedding depends on not only the model configurations but also the turbulence around the structure. The building models with different configurations including chamfer, crown opening, and porous crown were tested in different turbulent conditions. The 10% chamfered ratio has a more considerable benefit in suppressing the intensity of vortex shedding compared with the 7.5% chamfered ratio. The slotted crown has a more beneficial effect in suppressing the wind-induced responses due to resonance caused by vortex shedding compared with the one without opening. The model with 50% crown porosity has a more considerable benefit in suppressing the intensity of vortex shedding compared with the solid crown. The model with turbulent condition both the suburban exposure and interference of surroundings has a more considerable benefit in disrupting the vortex shedding compared with the model in open exposure without interference.

Effect of corner modifications on wind-induced responses of tall buildings

Any tall building subjected to high-speed winds will tilt and crack unless precautionary measures are taken. Various active and passive control methods are proposed to control the wind induced responses of the tall buildings. These tall structures can be made aerodynamic by modifying the external geometry of the building. In the present study, minor geometrical modifications are rendered to the structures. G+30 storeys are considered for each model with constant plan layout. The location of the building is considered to be Bengaluru and corresponding wind load data is considered. Modeling and analysis is carried out using ETABS 2017 software. Wind load analysis is carried out to know the effect of these aerodynamic modifications. The parameters considered for the comparison are storey displacement, natural time period and overturning moment. On comparative analysis, it was observed that wind-induced responses of these geometrically modified buildings have reduced by 5% to 10%. It can also be concluded that minor modifications have shown significantly better performance than a conventional square-plan building in addition to an innovative architectural look.

Effect of the combined aerodynamic control on the amplitude characteristics of wind loads on a tall building

Experimental investigation of the amplitude characteristics of wind loads on a square cross-sectional tall building under the combined aerodynamic control, which consists of the shape modification and air suction, has been conducted, and the effects of the suction flux coefficients CQ and wind direction angles on the wind pressure coefficients and aerodynamic force coefficients of five test models (includes a square cylinder and its corner modifications such as recession and chamfer, tapered cylinder and Y-shaped cylinder, and they are denoted as the Models 1–5 respectively) with and without air suction control have been analyzed. The Model 1 without suction control is defined as the benchmark model. The results show that the shape modifications have significant control effects on the mean and RMS pressure drag coefficients (CD and CσD) as well as the RMS pressure lift coefficient CσL of the Models 2, 3 and 5 at 0° wind direction, with the maximum reduction rates (CDR, CσDR and CσLR) of 39.2%, 44.0% and 38.4% for the Models 2, 5 and 2 respectively. When compared with the benchmark model, the most significant control effects of the combined aerodynamic control on CDR, CσD and CσL of the Models 2–5 with the suction speed of 9 m/s are also at 0° wind direction, with the maximum reduction rates of 61.8%, 65.8% and 5.7% for the Models 2, 2 and 5 respectively, which indicates that the combined aerodynamic control is more effective on the drag reduction than the passive or active aerodynamic control individually, and the Model 2 with suction control has the best wind-resistant performance. This study contributes to an effective aerodynamic measure to control the amplitude characteristics of wind loads on tall buildings, which can be an important reference for further studies or potential engineering applications of the combined aerodynamic control in mitigating the wind loads and wind-induced responses of tall buildings.

Time-domain model for prediction of generalized 3DOF buffeting response of tall buildings using 2D aerodynamic sectional properties

A time-domain method to calculate the buffeting response of a rectangular tall building (AR of B/D = 1.5 and H/D = 6) in along-wind, across-wind and torsional degrees of freedom using 2D aerodynamic sectional properties is presented here. The aerodynamic sectional properties were identified first using wind tunnel section models. Aerodynamic damping, which is critical in wind-induced response analysis of tall buildings, was calculated using the identified aeroelastic derivatives (flutter derivatives) and validated by comparing with those extracted directly from the response measurements of aeroelastic models of the tall building. A good agreement between the numerically simulated responses and the experimental measurements of an aeroelastic model (1:175 scale) shows the capability of the proposed method in the prediction of generalized 3DOF buffeting response of tall buildings in a wide range of wind speeds. Furthermore, the response of a tall building with two other cross-sectional shapes, circular and elliptical, was calculated using the developed method and compared amongst the three cross-sectional shapes to study the effect of cross section on buffeting response. The relative dependency of buffeting response of a tall building along each of the 3DOF on cross section, wind speed as well as angle of attack was assessed. Finally, the effect of taper on tall building’s buffeting response was studied using the developed method which showed that taper could significantly reduce the wind-induced response of tall buildings. The time-domain method to assess wind loads and buffeting response of tall buildings based on experimentally or theoretically derived aerodynamic properties of two-dimensional sections, as presented here, provides a viable and perhaps the only alternative to methods based on aeroelastic model tests and CFD simulations.

Evaluation of modal contribution to the wind-induced responses of tall buildings

The frequency domain analysis of structures requires the computation of the frequency response functions (FRF) matrix. Obtaining the FRF matrix is a time-consuming procedure, especially for the structures having large number of degrees of freedom (DOF). For the lightly damped structures, the FRF matrix can be estimated by the superposition of the structure’s dominant modes. In the present study, the modal dominancy analysis is carried out on the wind-induced responses of tall buildings using the frequency domain modal decomposition method. Two examples of tall structures, including a tall building and a tall TV tower are presented. It is found that the wind-induced dynamic displacement response is dominated by the first vibration mode and the effect of the higher modes can be neglected. For the acceleration response, contribution of the higher modes is observed. However, due to low-frequency content of the wind force spectrum, the first mode has the highest effect on the acceleration response. It is also demonstrated that the modal superposition method with contribution of the dominant modes can significantly reduce the order of the FRF matrix and the computing time.

Real-time aerodynamics hybrid simulation: Wind-induced effects on a reduced-scale building equipped with full-scale dampers

As buildings are designed to be taller and more slender, they become lighter and more flexible with less inherent damping. If left uncontrolled, excessive wind-induced building response can cause serious safety and serviceability issues. Additional damping provided by adding an auxiliary damping system to the tall building is considered as one of the most cost-effective means to suppress the wind-induced response. Typically, the performance of these damping systems is evaluated experimentally with scaled damper and building models. However, the simplified small-scale dampers may not truly reflect the complex behavior of the full-scale damping systems. To realize the effective reduction of the wind-induced response of tall buildings, a real-time aerodynamics hybrid simulation (RTAHS) methodology that can offer improved response evaluation of a tall building integrated with an auxiliary damping system is introduced in this study. In this novel dynamic testing approach, the accurate evaluation of wind-induced tall building response is achieved by interacting an aeroelastic model of the tall building with the numerical model of the full-scale damper via interfacing actuators during the wind-tunnel tests. The feasibility and simulation accuracy of the proposed dynamic testing technique in the wind tunnel is numerically demonstrated by two case studies involving the wind-induced response reduction of a tall building equipped with both small-scale and full-scale damper properties.

Combination of High- and Low-Rate GPS Receivers for Monitoring Wind-Induced Response of Tall Buildings.

High-rise buildings are susceptible to wind-induced displacements, which can be precisely monitored by using GPS technology. However, GPS monitoring applications may be subject to signal interference and high hardware costs. This study presents a new wind-induced vibration monitoring approach that is based on the mixed use of high-rate and low-rate GPS receivers. In the proposed approach, high-rate receivers are only required in the monitoring stations, where we apply time-differenced positioning to obtain position changes between adjacent epochs. The derived high-rate monitoring station position changes are then integrated with low-rate single epoch relative positioning results between the monitoring and reference stations. Experimental results with both simulated and real data show that the proposed method has a comparable performance with the traditional relative positioning approach, in terms of determining buildings’ vibration frequency, displacement, and acceleration.

Wind-induced responses of tall buildings under combined aerodynamic control

The new trend towards constructing taller buildings makes modern tall buildings be increasingly susceptible to wind excitations. Therefore, a combined aerodynamic control, including the shape optimization of the cross-section (passive aerodynamic control) and air suction (active aerodynamic control), is put forward to achieve a more considerable reduction of the wind-induced responses of a tall building with square cross-section, so as to improve its wind-resistance performance. Firstly, based on the wind excitations acquired by wind tunnel test of four suction controlled tall building models with different cross-sections (consists of the square, corner-recessed square, corner-chamfered square and Y-shaped cross-sections, and are denoted as Models 1–4 respectively), the wind-induced responses of the prototype tall buildings and simplified mass-spring models are calculated using the time history analysis method. Secondly, effects of the suction flux coefficient CQ, shapes of the cross-sections and wind direction angles θ on the characteristics of the wind-induced responses are analyzed. The results show that the combined aerodynamic control is very effective in reducing the along-wind and across-wind responses at most cases, however, it can sometimes be unfavorable to the torsional responses. Among the four tall buildings, Model 2 has the best performance in the along-wind direction, with a maximum reduction of the extremum tip displacement of 34% caused by the shape optimization, and 29% caused by the air suction and a total of 63% caused by the combined aerodynamic control at a relatively low CQ (CQ = 0.0159). However, the regularity is quite different for the across-wind responses; when θ is equal to 0°, the maximum reduction of the extremum tip displacement in the across-wind direction caused by the shape optimization and air suction are 49% for Model 4 and 47% for Model 1 respectively. Finally, a quantitative discussion on the reduction of the wind-induced responses of tall buildings caused by the combined aerodynamic control is conducted, which can provide a valuable reference for further studies or potential engineering applications.

Wind Loads on Tall Buildings: A Comparative Study of the International Wind Codes and Numerical Simulation

Wind codes and standards have been used commonly when designing regularshaped tall buildings to withstand wind loads. High-Frequency Base Balance (HFBB) data analysis and Computational Fluid Dynamics (CFD) have now emerged as alternative techniques to these wind codes and standards. This paper compares wind-induced building responses estimated from CFD analysis and those obtained using major international wind codes: AS/NZS1170.2:2011 (Australia/New Zealand), AIJ-RLB-2004 (Japan) and Eurocode-2005 (Europe), with HFBB predictions. The initial comparison was done on a rectangular 60-storey building model and subsequently, the study was extended to building models with different b/d ratios (breadth/depth) under three height categories. The results show that there are minor discrepancies between the code-predicted alongwind responses and those obtained using different approaches with different b/d ratios. Moreover, the across-wind responses predicted by the wind codes significantly deviate from the HFBB results, especially when the wind direction is normal to the shorter face of the building. The deviations intensify as the b/d ratio decreases. Nevertheless, the CFD predictions correspond well with the HFBB predictions for along-wind responses having deviations under 10%, highlighting the capability of CFD simulation for predicting global wind-induced responses of tall buildings.

Evaluation of wind loads and wind induced responses of a super-tall building by large eddy simulation

Taipei 101 Tower, which has 101 stories with height of 508 m, is located in Taipei where typhoons and earthquakes commonly occur. It is currently the second tallest building in the world. Therefore, the dynamic performance of the super-tall building under strong wind actions requires particular attentions. In this study, Large Eddy Simulation (LES) integrated with a new inflow turbulence generator and a new sub-grid scale (SGS) model was conducted to simulate the wind loads on the super-tall building. Three-dimensional finite element model of Taipei 101 Tower was established and used to evaluate the wind-induced responses of the high-rise structure based on the simulated wind forces. The numerical results were found to be consistent with those measured from a vibration monitoring system installed in the building. Furthermore, the equivalent static wind loads on the building, which were computed by the time-domain and frequency-domain analysis, respectively, were in satisfactory agreement with available wind tunnel testing results. It has been demonstrated through the validation studies that the numerical framework presented in this paper, including the recommended SGS model, the inflow turbulence generation technique and associated numerical treatments, is a useful tool for evaluation of the wind loads and wind-induced responses of tall buildings.

The effect of soil–foundation–structure interaction on the wind-induced response of tall buildings

The aim of this work is to provide a contribution towards the qualitative and quantitative assessment of soil–foundation–structure interaction effects on the dynamic response of tall buildings founded on relatively rigid rafts, and subjected to wind loading. The mechanical response of the soil–foundation system is modeled using two different approaches: in the first, the (visco)elastic system response is defined in terms of impedance coefficients; in the second, an inelastic, 6 DOF macroelement recently proposed for shallow foundations on coarse-grained soils is adopted. The macroelement approach allows to account for the non-linear and irreversible behavior of the soil–foundation system, and to consider the experimentally observed coupling between the different degrees of freedom in the inelastic regime. The results of a series of numerical simulations highlight the importance of considering SFSI effects in the analysis, and allow to identify the effects of the different constitutive assumptions made for the soil–foundation system. In particular, it is found that the permanent displacements and rotations accumulated at the foundation level in the inelastic simulations can give rise to significant permanent displacements at the building top. Moreover, significant differences are observed on the predicted forces and moments distribution at the building base for the two SFSI approaches considered.

A design procedure of two-way liquid dampers for attenuation of wind-induced responses of tall buildings

A new design procedure of a two-way liquid damper which reduces wind-induced responses of a tall building is presented as a quick guide for structural engineers. The two-way liquid damper combines the (1) Tuned Liquid Column Damper (TLCD) in which liquid moves through a U-shape tube and the (2) Tuned Sloshing Damper (TSD) in which liquid sloshes within a container, respectively for two orthogonal directions. Dimensions of the damper, such as horizontal liquid column length and the thickness of the TLCD, the width of the TSD, and liquid height are determined given the condition of tuning the natural frequencies of liquid motion in the damper to those of the building. The design procedure is a trial and error process of satisfying geometrical constraints (i.e., maximum space where the damper is installed) and varying controlled response factors (i.e., performance of vibration attenuation). A design example of the damper is illustrated in the paper for its installation at a 64-story reinforced-concrete residential building.

Dynamic response estimation of tall buildings with 3D modes: A probabilistic approach to the high frequency force balance method

The estimation of the wind-induced response of tall buildings is often carried out through the use of high frequency force balance (HFFB) tests. This technique is characterized by its versatility and rapidity of use, especially in comparison to other experimental methods. Nevertheless, the estimates of the structural response that can be obtained from its application are affected by uncertainties due to the lack of knowledge on the pressure field over the building surface. The importance of this is particularly relevant in the case of modern tall buildings with their complex geometric shapes and 3D and non-linear modes.This paper presents a novel approach for dealing with this possible source of error in the response estimation. In particular the uncertain spectral structure of the floor loads is modeled through a limited number of probabilistic parameters. This allows the definition of a local level fragility model that includes both the uncertainties inherent to the HFFB technique and the aleatory nature of the aerodynamic loads. The proposed model is applied to a case study building presenting non-linear 3D modes.

Effects of taper and set-back on wind force and wind-induced response of tall buildings

Advances in structural materials and construction methods have resulted in flexible and light tall buildings, making an assessment of structural safety during strong wind and serviceability/habitability during comparable medium/weak wind important design criteria. So far, lots of studies on suppressing the wind-induced responses have been carried out for tall buildings with aerodynamic modification. Most of the studies on aerodynamic modification have forced on the corner modification, while the studies on taper and set-back are limited. Changes of sectional shape through taper and set-back can modify the flow pattern around the models, encouraging more 3-dimensionalities, which results in reducing the wind-induced excitations. This paper discusses the characteristics of overturning moments and wind-induced responses of the tall buildings with height variations. The reduction of mean along-wind and fluctuating across-wind overturning moments are apparent in the suburban area than in urban area. A series of the response analyses, the rms displacement responses of the tall buildings with height variations are reduced greatly, while the rms acceleration responses are not necessarily reduced, showing dependences on wind direction.

초고층 건물의 양방향 풍응답 제어를 위한 액체댐퍼 실험

This study deals with the design of a bi-directional damper using a tuned liquid damper(TLD) and a tuned liquid column damper(TLCD) for a SDOF building. Two dampers are usually needed to reduce wind-induced responses of tall buildings since they are along and across wind ones. The proposed damper has the advantage of controlling both responses with a single damper. The damper used in this study behaves as both a TLCD in a specific translational direction and a TLD in the other orthogonal direction. This paper presents experimental verification to confirm its control performance. First, shaking table test is carried out to investigate reducing responses by the damper. Control performance of the damper is expressed by the transfer function from shaking table accelerations to SDOF building ones. Testing results show that the damper reduced bi-directional responses of a SDOF building. Also, it reduced torsion responses.

A New Model for Estimating Wind-induced Responses of Tall Buildings with Consideration of Cross-term between Background and Resonant Components

In current design practice, the responses of buildings and structures to fluctuating wind loads are usually separated into the background and resonant components, based on the assumption that these two components are not correlated with each other. The present paper proposes a new model for estimating the wind-induced responses of tall buildings, in which the background and resonant components and their cross-term are strictly defined and included. Therefore, the new model is more exact than the conventional ones. Comparisons are made for the along-wind and across-wind responses of tall buildings between this model and the conventional ones, based on a parametric investigation. The results show that the conventional models give results similar to those obtained from the new model for the along-wind responses, but generally underestimate the across-wind responses. Finally, some conclusions and useful suggestions are presented.

TLCD와 TSD를 이용한 새로운 형태의 양방향 감쇠기 설계변수

A new type bi-directional damper using a tuned liquid column damper(TLCD) and a tuned sloshing damper(TSD) is introduced in this study. Two dampers are usually needed to reduce wind-induced responses of tall buildings since they are along and across wind ones. The proposed damper has the advantage of controlling both responses with one damper. One of objectives of this study is to derive analytical dynamics to investigate coupled effects due to TLCD and TSD. Another objective is to address the effect of coupled control force due to TLCD and TSD on the dynamic characteristic of the damper based on analytical dynamics. Shaking table test is undertaken to experimentally grasp dynamic characteristics of the damper under white noise excitation. Its dynamic characteristic is expressed by the transfer function from the shaking table acceleration to the control force generated from the damper. Finally, its design parameters are identified based on the coupled dynamics, which include the mass ratio of horizontal liquid column to total liquid for a TLCD, the participation factor of the fundamental liquid sloshing for a TSD and damping ratio for both cases.

Monitoring the wind-induced response of tall buildings: GPS performance and the issue of multipath effects

The in-situ verification of structural performance under the action of wind requires monitoring technologies capable of capturing not only the resonant response features, but also the background and mean response components. This study explores the use of high-precision global positioning systems (GPS) toward that end. In this study, the performance of GPS for resonant response tracking is first validated in full scale against accelerometers, and then its ability to track both background and resonant response data is verified through controlled field tests. As the valuable low-frequency regime of this sensing technology is often compromised by long-period distortions known as multipath effects; this study then presents a means to characterize this phenomenon using Fourier and wavelet spectra and the GPS Distortion Signature. The latter diagnostic is shown to isolate multipath effects in controlled field testing. However, even when a GPS Distortion Signature is not available on-site, it is shown that multipath effects can still be removed by filtering to permit a rare comparison of the relative contributions of background and resonant responses in full scale to wind tunnel predictions.