Dynamic Wind Loads Research Articles

Full-Scale Validation of Dynamic Wind Load on a Super-Tall Building under Strong Wind

AbstractThis paper presents work on validating the dynamic wind load predicted by a wind tunnel model with the values identified from full-scale field vibration data of a super-tall building in Hong Kong. Dynamic wind load in this work refers to the power spectral density (PSD) of the modal force near the natural frequency of a particular mode of the building, in the context of random vibration with stationary loading and response. This quantity reflects the turbulence characteristics integrated over the building body and is of importance in wind engineering design. This study presents a method to predict the modal PSD of wind load of the first two translational modes of a tall building. The method combines wind tunnel test information and mean wind data available in the free field; the latter taken to be at the Waglan Island station maintained by the Hong Kong Observatory. On the full-scale side, although the modal PSD is not directly observable, it is identified from field vibration data measured at the...

Experimental and computational simulation for wind effects on the Zhoushan transmission towers

Long-span transmission tower and conductor line systems become important infrastructures in modern societies. The analysis of wind-induced dynamic responses of transmission towers is an essential task in the design of spatial lattice tower structures. Wind effects on the world's tallest transmission tower are presented in this paper. The tower with a total height of 370 metres, part of the Zhoushan long-span transmission project, enables high voltage conductor lines to span as long as 2750 metres over the typhoon-prone sea strait. A multi-DOF aeroelastic model test with and without conductor lines was carried out to investigate the dynamic performances of Zhoushan tower during typhoon events. Using the response measurement results in the wind tunnel, the inertial force based gust loading factors (GLFs) are applied to represent dynamic wind load effects on the tower for structural design purposes. Time domain computational simulation approach is also employed to predict dynamic responses of the transmission tower and the displacement based gust response factors (GRFs). The fair comparison of GLFs or GRFs are made between the results of the experimental approach and the computational simulation approach, which is an effective alternative way for quickly assessing dynamic wind load effects on high-rise and complex tower structures.

Computational aspects of simulating wind induced ovalling vibrations in silo groups

During a storm in October 2002, wind induced ovalling vibrations were observed on several empty silos of a closely spaced group of eight by five thin-walled silos in the port of Antwerp (Belgium). To determine realistic dynamic wind loads and hence clarify the cause of the wind induced ovalling vibrations in the silo group, 2D URANS simulations are performed for seven angles of incidence between 0° and 90°. The emphasis in this paper is on the extensive verification and validation of the simulations to ascertain the accuracy of the numerical results. Subsequent analysis of the fluctuating wind pressures on the silo surfaces shows that ovalling oscillations of the eigenmodes with three and four circumferential wavelengths will be induced at the lee side of the silo group, corresponding to the lowest structural eigenfrequencies of the silos and the pattern of the visually detected vibrations during the 2002 storm.

Behavior of a Nuclear Power Plant Ventilation Stack for Wind Loads

This paper describes behavior of self supporting tall reinforced concrete (RC) ventilation stack of a nuclear power plant (NPP) for wind loads. Since the static and equivalent dynamic wind loads are inter-dependant on overall size of the stack, proper sizing of the stack geometry is important for reducing wind loads. The present study investigated the influence of engineered backfill soil on lateral response of ventilation stack. Ignoring backfill soil stiffness up to ground height does not allow to predict actual critical wind velocity causing across wind oscillation. The results show that proposed modification in the stack geometry modeled using 2D beam-spring elements is economical than that of single tapered geometry. Shaft diameter reduced in the proposed geometry indicates that there is a scope for overall space savings in the NPP layout.

Power Spectral Density Model of Torsional Dynamic Wind Loads on Tall Buildings

9 models of tall buildings with different rectangular cross-sections are tested in a wind tunnel. After processing and analyzing the measured data of fluctuating pressure on the models, the effects of models’height, aspect ratio, side ratio on the power spectra of torsional wind loads are studied. New formulas of power spectral density of torsional wind loads are proposed by curve fitting method. The applicability of the formulas has been verified by the results from the wind tunnel test.

Tension bar systems under cyclic loading

The aim of the research presented in the paper is to clarify the behaviour of tension bar systems under cyclic loading. These components may be subjected to climatic conditions, especially to dynamic wind load, which may cause their vibrations. If the wind load were significantly influencing behaviour of the structure, the non negligible combination of normal force and bending moment would occur in the bar. Members used on bridges are additionally subjected to effects of cyclic traffic loads. Both dynamic wind load and traffic loading are major actions causing high-cycle fatigue of civil engineering structures and bridges.

Real-time estimation of dynamic wind load on a structure

Real-time estimation of dynamic wind load on a structure

Dynamic wind loads and wake characteristics of a wind turbine model in an atmospheric boundary layer wind

An experimental study was conducted to characterize the dynamic wind loads and evolution of the unsteady vortex and turbulent flow structures in the near wake of a horizontal axis wind turbine model placed in an atmospheric boundary layer wind tunnel. In addition to measuring dynamic wind loads (i.e., aerodynamic forces and bending moments) acting on the wind turbine model by using a high-sensitive force-moment sensor unit, a high-resolution digital particle image velocimetry (PIV) system was used to achieve flow field measurements to quantify the characteristics of the turbulent vortex flow in the near wake of the wind turbine model. Besides conducting “free-run” PIV measurements to determine the ensemble-averaged statistics of the flow quantities such as mean velocity, Reynolds stress, and turbulence kinetic energy (TKE) distributions in the wake flow, “phase-locked” PIV measurements were also performed to elucidate further details about evolution of the unsteady vortex structures in the wake flow in relation to the position of the rotating turbine blades. The effects of the tip-speed-ratio of the wind turbine model on the dynamic wind loads and wake flow characteristics were quantified in the terms of the variations of the aerodynamic thrust and bending moment coefficients of the wind turbine model, the evolution of the helical tip vortices and the unsteady vortices shedding from the blade roots and turbine nacelle, the deceleration of the incoming airflows after passing the rotation disk of the turbine blades, the TKE and Reynolds stress distributions in the near wake of the wind turbine model. The detailed flow field measurements were correlated with the dynamic wind load measurements to elucidate underlying physics in order to gain further insight into the characteristics of the dynamic wind loads and turbulent vortex flows in the wakes of wind turbines for the optimal design of the wind turbines operating in atmospheric boundary layer winds.

Finite Element Study of the Windage of Suspension Insulator String under Steady Wind and Gust

Considering the drawbacks exist in the traditional computational methods, we introduce a finite element method to analyze the windage of suspension insulator strings under the effects of dynamic and random wind loads. The windage of suspension insulator strings in the high voltage transmission line and influenced by static and random wind loads are simulated by using the finite element software. The result shows that the windage of suspension insulator strings subjected to the random wind loads is greater than the counterpart obtained through the statics methods.

Wind Uplift Performance of Composite Metal Roof Assemblies

A common factor in roof failures is wind forces, which inflict considerable damage every year, even to new roof structures. Metal roofs are a popular low-sloped roof assembly. On the basis of their layout, metal roofs can be categorized as either composite or noncomposite assemblies. In North American practice, five main test procedures—ASTM E1592, ANSI/FM 4474, UL 580, UL 1817, and CSA A123.21-04—are used to determine the wind uplift performance of metal roofs. The fundamental differences between these test protocols lie in the way they represent wind effects on the performance of metal roofing systems. Of the five, CSA A 123.21-04 is the only one that assesses the wind uplift resistance under dynamic wind load conditions. To evaluate the wind uplift performance of noncomposite and composite metal roofing assemblies, eight assemblies with two different types of panels—SNAP-IT and MR-24—were tested by using the CSA A123.21-04 dynamic test protocol. By relating air intrusion characteristics of the subsurface components to panel behavior, this paper shows how composite assemblies resist wind uplift pressures better than noncomposite assemblies. This paper reveals that increased air intrusion resistance of the sub surface components in composite assemblies results in increased suction resistance, decreased panel deflection, decreased stress on the panels, and increased wind uplift resistance.

Wind effect on milad tower using computational fluid dynamics

AbstractMilad tower is located in Tehran, Iran, and is a 436‐m telecommunication tower ranked as the fourth tallest structure in the world. Because of its specific use and also because of highly sensitive communication devices installed on the tower, nonlinear deformations under future severe winds and earthquakes should be studied. In this paper, a comprehensive study is carried out to investigate the effect of wind on this tower. The techniques of computational fluid dynamics, such as large eddy simulation (LES), Reynolds Averaged Navier–Stokes Equations (RANS) model and so on, were adopted in this study to predict wind loads on and wind flows around the building. The calculated results are compared with those of wind tunnel test. It was found through the comparison that the LES with a dynamic subgrid‐scale model can give satisfactory predictions for mean and dynamic wind loads on the specific structure of Milad tower, 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. Copyright © 2009 John Wiley & Sons, Ltd.

Wind Engineering on the New Millennium Bridge in South Korea

The New Millennium Bridge in Lot 1 of the Amtae∼Aphae Fixed Link, is a FCM-anchored hybrid two-pylon cable stayed bridge consisting of its high (195m) and low (135m) pylon with two bundle cables in the back span and the pre-construction of the side span method during erection is considered to improve the aerodynamic stability. The design of the bridge for wind was carried out based on extensive numerical analyses and wind tunnel tests: extreme wind climate analysis for typhoon, dynamic wind load (buffeting) analysis, computational fluid dynamics (CFD) analysis and sectional model tests etc. A series of wind tunnel tests were performed to find the harmful windinduced vibrations: vortex-shedding, buffeting, and flutter. Moreover, some alternatives of the deck section were investigated to find an optimized one for a super long span bridge.

Large eddy simulation of wind effects on a super-tall building

A new inflow turbulence generation method and a combined dynamic SGS model recently developed by the authors were applied to evaluate the wind effects on 508 m high Taipei 101 Tower. Unlike the majority of the past studies on large eddy simulation (LES) of wind effects on tall buildings, the present numerical simulations were conducted for the full-scale tall building with Reynolds number greater than <TEX>$10^8$</TEX>. The inflow turbulent flow field was generated based on the new method called discretizing and synthesizing of random flow generation technique (DSRFG) with a prominent feature that the generated wind velocity fluctuations satisfy any target spectrum and target profiles of turbulence intensity and turbulence integral length scale. The new dynamic SGS model takes both advantages of one-equation SGS model and a dynamic production term without test-filtering operation, which is particular suitable to relative coarse grid situations and high Reynolds number flows. The results of comparative investigations with and without generation of inflow turbulence show that: (1) proper simulation of an inflow turbulent field is essential in accurate evaluation of dynamic wind loads on a tall building and the prescribed inflow turbulence characteristics can be adequately imposed on the inflow boundary by the DSRFG method; (2) the DSRFG can generate a large number of random vortex-like patterns in oncoming flow, leading to good agreements of both mean and dynamic forces with wind tunnel test results; (3) The dynamic mechanism of the adopted SGS model behaves adequately in the present LES and its integration with the DSRFG technique can provide satisfactory predictions of the wind effects on the super-tall building.

Effective Use of Transfer Plates in Mixed Development

The need for providing car parking within apartment buildings often lead to a situation where different grid arrangements exist in the parking and apartment floors. In most cases, a setback is also present to accommodate this change over. This requires the use of a transfer system such as a transfer plate or transfer beams. In mixed development, there is a possibility to change the location of the transfer floor. This paper explores the added advantage of using a transfer plate in such situations due to its outrigger behaviour and how it changes when its location is changed. A case study of a highrise apartment building is used to demonstrate different trends in outrigger behaviour with respect to dynamic wind and earthquake loading.

An integrated design technique of advanced linear-mode-shape method and serviceability drift optimization for tall buildings with lateral–torsional modes

The advance to ever-taller and complex-shaped buildings requires a more accurate determination of dynamic wind loads for structural design purposes through wind tunnel tests. The three-dimensional (3D) mode shapes found in complex tall buildings complicate the use of the high frequency base balance (HFBB) technique for predicting wind-induced loads and effects. The linear-mode-shape (LMS) method was recently proposed to address some of the complications in the calculation of the generalised wind forces, which serve as the input to modal analysis for predicting wind-induced dynamic responses of tall buildings. The advanced linear-mode-shape (ALMS) method, a modification of the LMS method, is developed in this paper by introducing torsional mode shape corrections to take into account the partial correlation of torques over building height. The ALMS method is then incorporated into the accurate complete quadratic combination (ACQC) method to form a comprehensive framework to predict the equivalent static wind loads (ESWLs) for structural design of tall buildings. Then, an automated stiffness optimization technique integrated with the ESWL framework is developed for serviceability drift design of complex tall buildings with 3D mode shapes. A 60-storey building with an asymmetric structural system tested in a wind tunnel is used as an illustrative example. Encouraging results demonstrate that the integrated design optimization technique is able to produce a more economical element stiffness distribution of the example building, satisfying multiple serviceability wind drift design criteria while allowing for an accurate update and determination of the equivalent static wind loads under multiple wind angle conditions.

Adventures in architectural aerodynamics

This paper presents the results of a series of wind engineering studies, including high-frequency force balance boundary-layer wind tunnel tests conducted to assess the wind effects relevant to the structural and serviceability design of a proposed 400+ m high-rise scheme in the Middle East. The development of the architectural scheme allowed the design team to explore different levels of porosity for the façade of the building over the top third of the structure. The primary aim of these studies was to optimise the building design, minimising the overall dynamic structural wind loading and wind-induced accelerations. Details of the structural lateral-stability system employed in the design and key considerations on the potential use of alternative devices are given. A detailed comparison of the wind-induced structural response for a nominally sealed scheme – taking into account the contribution of additional damping – against the benefits arising from the employment of a permeable solution is presented. The technical challenges are illustrated from both a structural and cladding design viewpoint – the latter being related to the use of a porous skin over the architectural feature at the top of the tower. A brief description of the planned next phase of wind engineering work – aimed to assess the overall wind loading applicable to the design of the porous envelope as well as the potential for wind-induced noise and vibration of its elements to occur – is also given.

Assessment of capacity curves for transmission line towers under wind loading

The recommended factored design wind load effects for overhead lattice transmission line towers by codes and standards are evaluated based on the applicable wind load factor, gust response factor and design wind speed. The current factors and design wind speed were developed considering linear elastic responses and selected notional target safety levels. However, information on the nonlinear inelastic responses of such towers under extreme dynamic wind loading, and on the structural capacity curves of the towers in relation to the design capacities, is lacking. The knowledge and assessment of the capacity curve, and its relation to the design strength, is important to evaluate the integrity and reliability of these towers. Such an assessment was performed in the present study, using a nonlinear static pushover (NSP) analysis and incremental dynamic analysis (IDA), both of which are commonly used in earthquake engineering. For the IDA, temporal and spatially varying wind speeds are simulated based on power spectral density and coherence functions. Numerical results show that the structural capacity curves of the tower determined from the NSP analysis depend on the load pattern, and that the curves determined from the nonlinear static pushover analysis are similar to those obtained from IDA.

Numerical Study on Dynamic Swing of Suspension Insulator String in Overhead Transmission Line under Wind Load

Numerical modeling of an overhead transmission line section and the digital simulation of stochastic wind field, to which the transmission line section is exposed, are presented. Time-domain analyses of typical transmission line sections in stochastic wind fields are carried out by ABAQUS software. It is discovered that the numerically determined dynamic swing angles of the suspension insulator strings in the transmission line sections are larger than those calculated with the formulas proposed in the technical code for designing overhead transmission lines. A dynamic wind load factor is suggested to be introduced into the formulas proposed in the design code.

Tall Building Motion Control Using Double Skin Façades

Double skin facade (DSF) systems are more effective environmental mediators than conventional single skin facade systems, and, due to this reason, their usage for tall buildings has increased despite their higher initial costs. This paper investigates the potential of the DSF system as a structural motion control device in tall buildings regarding dynamic wind loads. The connectors between the inner skins and outer skins of the DSF system are designed to have very low axial stiffness with a damping mechanism so that the dynamic motion of the primary building structure can be reduced. Governing equations are generated for motion of both the primary structures and DSF outer skins and solved to anticipate the dynamic responses of the system. The primary structure motion can be substantially reduced by the low stiffness DSF connector design introduced in this paper. However, the excessive motion of the DSF outer skins is a serious design limitation of the system. Further research is required for the practical application of the proposed system.

Wind-induced vibration control of Hefei TV tower with fluid viscous damper

The Hefei TV tower is taken as an analytical case to examine the control method with a fluid viscous damper under wind load fluctuation. Firstly, according to the random vibration theory, the effect of fluctuating wind on the tower can be modeled as a 19-dimensional correlated random process, and the wind-induced vibration analysis of the tower subjected to dynamic wind load was further obtained. On the basis of the others’ works, a bimodel dynamic model is proposed. Finally, a dynamic model is proposed to study the wind-induced vibration control analysis using viscous fluid dampers, and the optimal damping coefficient is obtained regarding the wind-induced response of the upper turret as optimization objectives. Analysis results show that the maximum peak response of the tower under dynamic wind load is far beyond the allowable range of the code. The wind-induced responses and the wind vibration input energy of the tower are decreased greatly by using a fluid viscous damper, and the peak acceleration responses of the upper turret is reduced by 43.4%.