Standard Tall Building Research Articles

Predicting wind-induced vibrations of high-rise buildings using unsteady CFD and modal analysis

This paper investigates the wind-induced vibration of the CAARC standard tall building model, via unsteady Computational Fluid Dynamics (CFD) and a structural modal analysis. In this numerical procedure, the natural unsteady wind in the atmospheric boundary layer is modeled with an artificial inflow turbulence generation method. Then, the turbulent flow is simulated by the second mode of a Zonal Detached-Eddy Simulation, and a conservative quadrature-projection scheme is adopted to transfer unsteady loads from fluid to structural nodes. The aerodynamic damping that represents the fluid–structure interaction mechanism is determined by empirical functions extracted from wind tunnel experiments. Eventually, the flow solutions and the structural responses in terms of mean and root mean square quantities are compared with experimental measurements, over a wide range of reduced velocities. The significance of turbulent inflow conditions and aeroelastic effects is highlighted. The current methodology provides predictions of good accuracy and can be considered as a preliminary design tool to evaluate the unsteady wind effects on tall buildings.

Computational evaluation of wind loads on a standard tall building using LES

In this paper, wind induced aerodynamic loads on a standard tall building have been evaluated through large-eddy simulation (LES) technique. The flow parameters of an open terrain were recorded from the downstream of an empty boundary layer wind tunnel (BLWT) and used to prescribe the transient inlet boundary of the LES simulations. Three different numerically generated inflow boundary conditions have been investigated to assess their suitability for LES. A high frequency pressure integration (HFPI) approach has been employed to obtain the wind load. A total of 280 pressure monitoring points have been systematically distributed on the surfaces of the LES model building. Similar BLWT experiments were also done to validate the numerical results. In addition, the effects of adjacent buildings were studied. Among the three wind field generation methods (synthetic, Simirnov's, and Lund's recycling method), LES with perturbation from the synthetic random flow approach showed better agreement with the BLWT data. In general, LES predicted peak wind loads comparable with the BLWT data, with a maximum difference of 15% and an average difference of 5%, for an isolated building case and however higher estimation errors were observed for cases where adjacent buildings were placed in the vicinity of the study building.

Multiscale finite element method applied to detached-eddy simulation for computational wind engineering

A multiscale finite element method is applied to the Spalart-Allmaras turbulence model based detached-eddy simulation (DES). The multiscale arises from a decomposition of the scalar field into coarse (resolved) and fine (unresolved) scales. It corrects the lack of stability of the standard Galerkin formulation by modeling the scales that cannot be resolved by a given spatial discretization. The stabilization terms appear naturally and the resulting formulation provides effective stabilization in turbulent computations, where reaction-dominated effects strongly influence near-wall predictions. The multiscale DES is applied in the context of high-Reynolds flow over the Commonwealth Advisory Aeronautical Council (CAARC) standard tall building model, for both uniform and turbulent inflows. Time-averaged pressure coefficients on the exterior walls are compared with experiments and it is demonstrated that DES is able to resolve the turbulent features of the flow and accurately predict the surface pressure distributions under atmospheric boundary layer flows.

Peak loading and surface pressure fluctuations of a tall model building

Using a recently developed inflow generation approach (Kim et al., 2013), Large-Eddy Simulation (LES) of the flow over the Commonwealth Advisory Aeronautical Council (CAARC) standard tall building has been performed. The surface pressure fluctuations were calculated and are shown to be in reasonable agreement with the measurements in the literature. Numerical experiments were conducted to investigate the effects of the inflow turbulence intensity and integral length scales. Previous research, e.g. Surry and Djakovich (1995) and Huang et al. (2007), suggests a presence of periodicity in the lateral forces on tall buildings, indicating a correlation of the surface pressures on the building's lateral faces. This paper also focuses on the correlations of surface pressure, local wall-normal forces and cross-wind velocity.

Peak Distributions and Peak Factors of Wind-Induced Pressure Processes on Tall Buildings

The emergence of performance-based wind engineering calls for improved probabilistic modeling of wind effects on buildings. This paper focuses on the development of probabilistic models of the peak distribution and peak factor for non-Gaussian processes and explores the applications of this development in wind engineering. The closed-form expressions for the mean, SD, and fractile levels of extremes are derived for a random process whose peaks are modeled by the parametric Weibull distribution. A new translated-peak-process method is then developed for the estimation of the peak distribution, peak factor, and variability of extremes, based on the Weibull distribution and point-to-point mapping procedure. The proposed translated-peak-process method is validated by wind-tunnel pressure measurements on a standard tall building and is shown to be more robust and practical than many existing methods in analyzing non-Gaussian wind pressure data.

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.

Aerodynamic and aeroelastic analyses on the CAARC standard tall building model using numerical simulation

The simulation of the wind action over the CAARC (Commonwealth Advisory Aeronautical Council) standard tall building model is performed in the present work. Aerodynamic and aeroelastic analyses are reproduced numerically in order to demonstrate the applicability of CFD techniques in the field of wind engineering. A major topic in this paper is referred to one of the first attempts to simulate the aeroelastic behavior of a tall building employing complex CFD techniques. Numerical results obtained in this work are compared with numerical and wind tunnel measurements and some important concluding remarks about the present simulation are also reported.

Numerical evaluation of wind effects on a tall steel building by CFD

A comprehensive numerical study of wind effects on the Commonwealth Advisory Aeronautical Council (CAARC) standard tall building is presented in this paper. The techniques of Computational Fluid Dynamics (CFD), such as Large Eddy Simulation (LES), Reynolds Averaged Navier–Stokes Equations (RANS) Model etc., were adopted in this study to predict wind loads on and wind flows around the building. The main objective of this study is to explore an effective and reliable approach for evaluation of wind effects on tall buildings by CFD techniques. The computed results were compared with extensive experimental data which were obtained at seven wind tunnels. The reasons to cause the discrepancies of the numerical predictions and experimental results were identified and discussed. It was found through the comparison that the LES with a dynamic subgrid-scale (SGS) model can give satisfactory predictions for mean and dynamic wind loads on the tall building, while the RANS model with modifications can yield encouraging results in most cases and has the advantage of providing rapid solutions. Furthermore, it was observed that typical features of the flow fields around such a surface-mounted bluff body standing in atmospheric boundary layers can be captured numerically. It was found that the velocity profile of the approaching wind flow mainly influences the mean pressure coefficients on the building and the incident turbulence intensity profile has a significant effect on the fluctuating wind forces. Therefore, it is necessary to correctly simulate both the incident wind velocity profile and turbulence intensity profile in CFD computations to accurately predict wind effects on tall buildings. The recommended CFD techniques and associated numerical treatments provide an effective way for designers to assess wind effects on a tall building and the need for a detailed wind tunnel test.

Direct measurement of wind-induced displacements in tall building models using laser positioning technique

This paper introduces a laser positioning measurement system with the aim of establishing a new technique in the direct measurement of wind-induced tip displacement of tall building models in simulated wind environment. The experiment was carried out on a semi-rigid aeroelastic model of the CAARC standard tall building of 1/375 length scale in the NUS-HDB boundary layer wind tunnel, National University of Singapore. The displacements measured using laser positioning technique were compared with those involving the conventional strain gauge. The paper also presents the application of this technique to measure the relative displacement between two building models.

Interference effects on wind-induced coupled motion of a tall building

Interference effects from neighbouring buildings on wind-induced coupled translational–torsional motion of tall buildings have been investigated through a series of wind tunnel aeroelastic model tests. Interference effects on the CAARC standard tall building by an 8:1:1 tall interfering building both upstream and downstream were investigated. The results indicated a significant increase in responses at the critical wind speed where the frequency of the shed vortices originated from the interfering building coincides with the modal natural frequency of vibration of the principal tall building. The along-wind, cross-wind, and twisting moment responses of the principal building were significantly increased when the interfering building was located diagonally upstream. A more substantial increase in responses was evident when the interfering building was located directly upstream from the principal building.

Effects of coupled translational-torsional motion and eccentricity between centre of mass and centre of stiffness on wind-excited tall buildings

Wind tunnel aeroelastic model tests of the Commonwealth Advisory Aeronautical Research Council (CAARC) standard tall building were conducted using a three-degree-of-freedom base hinged aeroelastic(BHA) model. Experimental investigation into the effects of coupled translational-torsional motion, cross-wind/torsional frequency ratio and eccentricity between centre of mass and centre of stiffness on the wind-induced response characteristics and wind excitation mechanisms was carried out. The wind tunnel test results highlight the significant effects of coupled translational-torsional motion, and eccentricity between centre of mass and centre of stiffness, on both the normalised along-wind and cross-wind acceleration responses for reduced wind velocities ranging from 4 to 20. Coupled translational-torsional motion and eccentricity between centre of mass and centre of stiffness also have significant impacts on the amplitude-dependent effect caused by the vortex resonant process, and the transfer of vibrational energy between the along-wind and cross-wind directions. These resulted in either an increase or decrease of each response component, in particular at reduced wind velocities close to a critical value of 10. In addition, the contribution of vibrational energy from the torsional motion to the cross-wind response of the building model can be greatly amplified by the effect of resonance between the vortex shedding frequency and the torsional natural frequency of the building model.

A two-degree-of-freedom base hinged aeroelastic (BHA) model for response predictions

Abstract An alternative aeroelastic modelling technique for the response predictions of tall buildings in two fundamental translational modes, namely a two-degree-of-freedom base hinged aeroelastic (BHA) model, is proposed. This modelling technique has all the advantages of the conventional “stick” model in terms of its simplicity and its ability to readily change the mass, stiffness, structural damping and geometry of the building model and also has the ability to model coupled translational–torsional motion (complex motion). It is found that the frequencies of vibration of the BHA model can be accurately predicted by means of a free-standing-cantilever model and the responses of the CAARC standard tall building in the along-wind and cross-wind directions observed by a BHA model are similar to those observed by a conventional “stick” model and other published records.

Wind-induced coupled translational-torsional motion of tall buildings

A three-degree-of-freedom base hinged assembly (BHA) for aeroelastic model tests of tall building was developed. The integral parts of a BHA, which consists of two perpendicular plane frames and a flexural pivot, enable this modeling technique to independently simulate building translational and torsional degree-of-freedom. A program of wind tunnel aeroelastic model tests of the CAARC standard tall building was conducted with emphasis on the effect of (a) torsional motion, (b) cross-wind/torsional frequency ratio and (c) the presence of an eccentricity between center of mass and center of stiffness on wind-induced response characteristics. The experimental results highlight the significant effect of coupled translational-torsional motion and the effect of eccentricity between center of mass and center of stiffness on the resultant rms acceleration responses in both along-wind and cross-wind directions especially at operating reduced wind velocities close to a critical value of 10. In addition, it was sound that the vortex shedding process remains the main excitation mechanism in cross-wind direction even in case of tall buildings with coupled translational-torsional motion and with eccentricity.

Seismic design of a tall building with energy dissipation damper for the attenuation of torsional vibration

This paper reports a structural design method of a 100 m tall building using passive energy dissipation dampers, which made the unique architectural form of the building structurally feasible. This tall building will have 21 floors above ground and three basement floors, and will be an educational facility in the city of Osaka. The shape of the building is a unique combination of a rectangular parallelepiped and a quadrangular pyramid with a spacious atrium and a spherical hall inside. The main structure is composed of rigid steel frames, and the outer ones are equipped with dampers. The passive energy dissipation dampers applied to this project are mild steel plates with honeycomb‒shaped openings and capable of large elasto‒plastic deformation. They are expected to perform good energy absorption during earthquakes. As they are installed between vertical spans inside columns, they are consistent with the architectural planning. A structural problem caused by torsional vibrations in the event of an earthquake would be serious if the complex form of the building had not been considered. One of the major objectives of implementing such dampers is the stiffness and strength enhancement that adjusts and reduces the torsional vibrations to the normal level commonly encountered in a standard tall building design process. Time‒history analysis is carried out using a dynamic model to examine the structural performance of the building, which proves that the building is kept intact even under a large earthquake whose peak velocity is 50 cm s−1. © 1998 John Wiley & Sons, Ltd.

Wind induced external pressures on a tall building with various corner configurations

Wind tunnel pressure measurements were conducted at 2 3 height on a 1:300 scale model of a tall building with various corner configurations based on the CAARC standard tall building. The aim was to investigate the effect of the different corner configurations on the magnitude and distribution of the peak pressure coefficients. The shapes included square, bevelled, rounded and recessed corners. The location and magnitude of the measured peak pressure coefficients, and the wind direction for which they occurred varied considerably for the different corner configurations.

Control of wind-induced tall building vibration by tuned mass dampers

Wind tunnel model tests and theoretical analyses were conducted to investigate the effectiveness of tuned mass dampers in suppressing wind-induced tall building motion. The tall building model was a 1:400 scale aeroelastic model of the CAARC Standard Tall Building. This model and the tuned mass damper models of different parameters were designed and tested in a wind tunnel with properly simulated atmospheric boundary layer flow. The aeroelastic test of the CAARC model demonstrated the effectiveness of the tuned mass damper system in suppressing the dynamic response of the building. The parametric study of passive tuned mass dampers, leading to theoretical analysis and design of an effective and efficient tuned mass damper system, was based on excitation spectra which were directly measured from the wind tunnel model tests. Semi-analytical results were in good agreement with the test results. The analytical results further indicated that the effectiveness of tuned mass dampers can be enhanced by the inclusion of an active control system.

Sensitivity of the CAARC standard building model to geometric scale and turbulence

This article describes a series of wind tunnel experiments performed to investigate the influence of errors in wind tunnel simulation on the response of the CAARC standard tall building model. The effect of distorting two parameters, namely the geometric scale of the model and the longitudinal turbulence profile, was investigated. It is concluded that a 50% change in the geometric scale produces negligible errors, while a change of t 50% in the intensity of longitudinal turbulence produces small but noticeable changes in the response of the building. It is also concluded that the discrepancies in the results for the CAARC model found in the literature are probably due to common experimental errors and differences in the measurement of the reference wind speed at the top of the building.

Test on the CAARC standard tall building model with a length scale of 1 : 1000

Both pressure and aeroelastic studies of the CAARC standard tall building with the linear scale of 1 : 1000 were carried out. The results are compared with the findings from other experimental works with much larger linear scales.

Effect of tuned mass dampers on wind induced response of tall buildings

The effectiveness of a tuned mass damper in suppressing wind-induced building motion was examined through both a mathematical analysis and a wind tunnel test. The dependence of the optimized design parameters on the characteristics of random excitaion was indicated in the first part. A 1:1000 scaled aeroelastic model of CAARC standard tall building was chosen for the wind tunnel test to demonstrate the damper's effectiveness. It is also interesting to find that even with this small scale the test results show good agreement with the prviously published CAARC results from the other institutions.

Comparison of measurements on the CAARC standard tall building model in simulated model wind flows

Measurements of surface pressures and response on the CAARC standard tall building model, made at six establishments, have been compared. In general, the degree of agreement was good and mostly within the scatter of reasonable experiemental accuracy. Small trends were observable in respect of pressure measurements which could be attributed to differences in the approaching longitudinal velocity spectrum and to the requirement for blockage corrections. There were no obvious trends in the dynamic response measurements where the majority of the data compared within ±15%.