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Enhancement of wind by bushfire, referred to as bushfire-wind enhancement phenomenon, causes damages to buildings located in bushfire-prone areas by increasing pressure load around the structures. This study focuses on the effects of point source aspect ratio (AR) on the wind enhanced by fire. FireFOAM solver of OpenFOAM platform is used to perform Large Eddy Simulation analysis for different fire source aspect ratios under two different fire source conditions: (i) identical fire intensity (fire heat release rate per unit area) and (ii) identical fire heat release rate conditions. Simulations were performed for three different fire source aspect ratios under these fire source boundary conditions. An appropriate normalization group based on fire source hydraulic diameter was introduced for fire-induced pressure gradient to explain the variation of wind enhancement with fire source aspect ratio. The results reveal that under a constant fire intensity condition, increasing the fire source aspect ratio causes a higher normalized fire-induced pressure gradient which leads to more intensified wind enhancement. In contrast, the increase of fire source aspect ratio while fire heat release rate is kept constant culminates in a reduction in the normalized fire-induced pressure gradient, reducing wind enhancement. Moreover, with the increase of the fire source aspect ratio, the area of counter-rotating vortices (CRV) where maximum wind enhancement occurs is expanded. The results also show that with the increase of fire source aspect ratio, the length of flame attachment to the ground immediately downstream of fire increases. In addition to the longitudinal wind enhancement, the effects of fire source aspect ratio on vertical velocity were also analyzed based on the Richardson number defined by hydraulic diameter and flow reference velocity. The effects of the aspect ratio on flame length were also studied. It was shown as a result of the increase of aspect ratio for one unit, flame length increases by approximately 14% and reduces by 7% under constant fire intensity and constant fire heat release rate condition, respectively.

This research investigates the effect of building cross-section shape on the air pollutant dispersion around an isolated building. A Computational Fluid Dynamic (CFD) model was developed and validated based on detailed wind tunnel experimental data. Both Large Eddy Simulation (LES) and Realizable k-e models were used for turbulence closure and LES was found to provide a better agreement with experimental results than the RANS model, particularly in replicating pollutant dispersion characteristics associated with wind-structure interaction. The LES model was then utilized to study the effect of building cross-section shape. Four building cross-section shapes, square, chamfered, curved and circular, along with different air pollutant emission locations were studied. It has been found that the area around an isolated building can be categorized into three emission regions, namely the windward critical emission region, the leeward critical emission region and the side non-critical emission region. The air pollutant emissions from the leeward critical emission region affect the building the most. Furthermore, the size of this region depends on the building cross-section shape, with the circular and curved buildings having a smaller leeward critical emission region than those for the chamfered and square buildings. Evidently, air pollutant dispersion around a building is dominated by wind-structure interaction which in turn is dependent on the building cross-sectional shape. These characteristics can be utilized to mitigate air pollutant dispersion in urban environments in conjunction with careful consideration of the air pollutant emission location relative to a building.

Substantial influence of fire flame on wind flow aerodynamic characteristics lead to enhancement of wind velocity that may cause considerable damages to buildings in bushfire-prone areas. Fire is associated with rotational vortical structures ranging from the small scales, sourced by baroclinic generation of vorticity ( ω B G V ), to large scale vortices arising from amalgamation mechanisms that can significantly affect wind flow characteristics during fire-wind interaction. This study aims to understand the extent to which baroclinic generation of vorticity affects wind enhanced by fire. Large eddy simulations (LES) of fire-wind interaction are conducted using fireFOAM solver of OpenFOAM platform for two different types of fuels with the aim to produce two different scenarios with similar heat release rate, but different flame temperatures. This will guarantee the production of different vortex structures in the two cases while flow expansion rate, which is proportional to the fire heat release rate, remains constant. FireFOAM solver was modified to extract fire-induced acceleration and vorticity components. The LES results show that under similar fire intensity and heat release rate conditions, wind enhancement is higher in the scenario with higher flame temperature along the centreline as well as the cross-sectional locations which are corresponding to the locations of counter-rotating vortices where the maximum wind enhancement appears. It was shown that in the case with higher flame temperature, baroclinic generation of vorticity is stronger, which causes stronger longitudinal fire-induced pressure gradient and consequently results in a higher wind enhancement in these cross-sectional locations. The distribution of maximum cross-sectional baroclinic generation of vorticity along longitudinal location are presented, confirming in both cases, baroclinic generation of vorticity reduces with an increase of distance from the fire source. However, in almost all distances, the scenario with a higher flame temperature generates stronger baroclinic generation of vorticity, so does the fire-induced pressure gradient and flow enhancement.

This paper proposes a novel hybrid aeroelastic-pressure balance (HAPB) technique for the measurement of unsteady aerodynamic force on a galloping prism. HAPB wind tunnel tests were performed to simultaneously observe the unsteady aerodynamic force and galloping response of a test model. The amplitude-dependent nonlinear damping and stiffness of the HAPB system that include the non-wind-induced aerodynamic force that is caused by the interaction between the oscillating model and its surrounding ‘still’ air were identified using a wavelet method. The non-wind-induced aerodynamic force was determined by a forced vibration technique. Subsequently, the galloping response was calculated by substituting the unsteady aerodynamic force and physical nonlinearities into the governing equation of motion. The results show that (1) the proposed HAPB technique is effective in obtaining unsteady crosswind forces; (2) the unsteady self-excited force with excluding the non-wind-induced aerodynamic force can accurately predict the galloping response of the test model whereas the classical quasi-steady theory fails for the prediction. This study has not only provided a HAPB used in wind tunnel, but also addressed shortcomings of the classical quasi-steady theory in predicting galloping instabilities of slender prisms.

Due to the complexity of crosswind vibrations of rectangular cylinders, current research on crosswind vibrations of rectangular cylinders mainly relies on expensive wind tunnel tests and time-consuming numerical simulation techniques. In this study, in order to evaluate crosswind vibrations of rectangular cylinders, machine learning method was used to build an efficient and effective prediction model for supplementing the above two research tools. 5 machine learning models based on decision tree regression, k-nearest neighbor regression, random forest, gradient boosting regression tree (GBRT) and histogram gradient boosting regression tree algorithms were trained based on the existing high-quality and reliable wind tunnel test datasets of crosswind responses of rectangular cylinders. The hyper-parameters were optimized by using particle swarm optimization method. 4 types of crosswind vibration phenomena, including over-coupled, coupled, semi-coupled and decoupled, were predicted. It was found that the GBRT model is capable of predicting crosswind responses of rectangular cylinders at side ratios from 0.75 to 3 and Scruton numbers from 0 to 150 under wind flow with turbulence intensities from 0 to 16%. Evidently, GBRT model can be an effective and economical method to study crosswind vibrations of rectangular cylinders and hence supplement traditional wind tunnel tests and numerical simulation techniques.

Topography-induced twisted wind flows are frequently observed in Hong Kong due to the abundance existence of mountains. Observed twisted wind profiles are with larger wind twist angles and are confined to the lower 500 m of the atmosphere, thus may impose significant effects on both structures and near-ground wind conditions. In order to investigate the influences of twisted wind flows on the pedestrian-level wind environment, two twisted wind profiles were simulated in a boundary layer wind tunnel by using 1.5 m tall wooden vanes. The maximum guide angles of vanes were 15° and 30° at the ground level to represent two nominal yaw angles of ‘high’ and ‘extreme’ twisted wind flows. Simulated twisted wind profiles followed the power-law profile and have acceptable longitudinal and lateral turbulence power spectra similar to conventional wind flows. The yaw angle profiles were exponentially decayed with the height but had smaller maximum yaw angles than of the guide vanes. The evaluation of wind conditions near an isolated building and a row of buildings in twisted wind flows has displayed substantially modified flow features such as asymmetric wind speed distributions about the building centre line and reduced wind speeds in the passages between buildings., Highlights • The characteristics of twisted wind profiles observed in Hong Kong are analysed. • A novel vane system is developed to simulate twisted wind profiles in a boundary layer wind tunnel. • The flow quality of simulated twisted wind profiles is evaluated. • The influence of twisted wind profiles on the pedestrian-level wind environment near a building and a building array is demonstrated.

The occupant response to wind-induced building motion is complex, governed by human physiology, and moderated by the psychological response to motion and discomfort within a sophisticated engineered environment. This paper aims to consolidate and critique the early research on the occupant response to building motion and to present recent multidisciplinary research that identifies a broader range of responses to, and consequences of, exposure to building motion. Recent field-based research shows that mild motion sickness, known as sopite syndrome, can cause significantly reduced work performance and occupant comfort. This is supported by laboratory-based physiological studies showing low-amplitude acceleration induces physiological changes in humans well below the threshold of motion perception (∼6·5 milli-g) which are consistent with the early onset of nausea. Current design criteria, based on perception thresholds, do not include the wider range of possible effects, particularly sopite syndrome and nausea. As a consequence, building occupants may suffer from a range of effects, including sopite syndrome and reduced work performance, that are not considered in current guidelines.

Tall buildings vibrate in response to strong winds at frequencies below 1 Hz, which can cause motion sickness and sopite syndrome in humans. Sopite syndrome is characterized by sleepiness, low motivation and low mood that can reduce productivity in office workers. This paper uses recent multidisciplinary research to estimate the cost of building motion on organizations in tall buildings, and provides a framework for future research. The potential costs of wind-induced building motion to organizations are highly variable, depending on the local weather climate, but are likely to be significant in the long-term. It is argued that wind-induced building motion is a negative externality, a cost of inadequate design passed to building users. A three-factor approach towards reducing adverse impacts of wind-induced building motion is discussed: (1) further research investigating the characteristics of motion that provoke sopite syndrome, (2) create a new generation of serviceability criteria, and (3) regu...

Previous studies on inter-unit dispersion are limited to isolated buildings. The influence of an upstream interfering building may significantly modify the indoor airflow characteristics of the wind-induced natural ventilated downstream interfered building. Motivated by the findings in previous studies, namely that infectious respiratory aerosols exhausted from a unit can re-enter into another unit in the same building through building envelope openings, this study investigates the inter-unit pollutant dispersion around a multi-story building in two wind directions by employing the computational fluid dynamics (CFD) method. The CFD model employed in this study has been validated against previous experimental data. The results show that the presence of an upstream building greatly changes the path lines around the downstream target building and the pollutant transportation routes around it. The presence of a low upstream building also greatly increases the average air exchange rate (ACH) values and the pollutant re-entry ratios (Rk) below the source unit on the windward side of the downstream target building for normal wind incidence. However, the presence of a high upstream building greatly increases the average ACH values on the windward side and increases the Rk on the leeward side of the downstream building for oblique wind incidence., Highlights • Interunit pollutant dispersion in a naturally ventilated building was investigated. • Effect of an upstream interfering building on the target building was examined. • A high and a low upstream buildings were considered. • An upstream building improves ventilation performance of the target building. • An upstream building enhances Interunit dispersion in the target building.

Wake-induced vibration of a small cylinder in the wake of a large cylinder was investigated numerically. The focus of the study is to identify the effects of the spacing between the two cylinders on the wake mode and the vibration of the small cylinder. Simulations were conducted for a diameter ratio of 0.5, a low mass ratio of 3, a Reynolds number of 200 (based on the diameter of the large cylinder) and three spacing ratios of S =1.5, 2 and 3. Four response regimes (regimes 1, 2, 3 and 4) have been identified depending on the spacing ratio and the reduced velocity. For S =1.5 and 2, the four regimes can be clearly identified by the disconnections of the amplitude-versus-reduced-velocity curves. For the largest spacing ratio of S =3, only regimes 1 and 3 are observed. Regime 1 is the low reduced velocity range where the response amplitude is small. It can be further divided into regimes 1A and 1B based on the variation of the amplitude in the in-line direction with the reduced velocity. In regime 2, the small cylinder is trapped in the wake of the large cylinder and the vortex shedding frequency of the large cylinder is close to the natural frequency of the small cylinder instead of following the Strouhal law. The maximum response amplitude occurs in regime 3, where the small cylinder is downstream the vortex formation zone of large cylinder. In regime 4, the smaller cylinder is attracted towards the large cylinder and fully immersed in the main wake vortices. Hysteresis is observed near the boundary between regimes 1 and 2 and near the boundary between regimes 2 and 3. In the hysteresis regions, the response of the small cylinder depends on how the fluid velocity at the inlet fluid velocity is initiated.

We perform Computational Fluid Dynamics (CFD) analyses of a low-rise building immersed in a turbulent boundary layer. The Silsoe 6 m cube is chosen as the main case study aiming at representing the key features of the typical wind conditions experienced by low-rise buildings. The turbulent inflow condition is generated by employing a precursor technique. A sensitivity study is conducted to investigate the effects of eight subgrid-scale (SGS) models on the flow around the cube. The incoming turbulence intensity and mesh sizing for each of the SGS models are also explored. The results in terms of time-averaged pressure fields for relatively well-resolved simulations are well compliant with available experimental data and insensitive to the selection of the SGS model. We demonstrate that, while the effect of the aforementioned factors has a limited impact on the first-order statistics of the pressure coefficients, their influence becomes much more pronounced when analysing higher-order statistics (i.e. variance, skewness and kurtosis) and extreme values. The extent of their relative importance depends on the location of the point under investigation and the quantity of interest. The current study provides guidelines on the choice of factors which can strongly affect the results obtained employing CFD simulations when the local peak pressures are of interest, for example, as in the case of cladding design.

Interference effects of tall buildings have attracted numerous studies due to the boom of clusters of buildings in megacities. To fully understand the interference effects, it often requires a substantial amount of wind tunnel tests. Limited wind tunnel tests that only cover part of interference scenarios are unable to fully reveal the interference effects. This study used machine learning techniques to resolve the conflicting requirement between limited wind tunnel tests that produce unreliable results and a completed investigation of the interference effects that is costly. Four machine learning models including decision tree, random forest, XGBoost, generative adversarial networks (GANs), were trained based on 30% of a dataset to predict wind pressure coefficients on the principal building. The GANs model exhibited the best performance in predicting these pressure coefficients. A number of GANs models were then trained based on different portions of the dataset ranging from 10% to 90%. It was found that the GANs model based on 30% of the dataset is capable of predicting pressure coefficients under unseen interference conditions accurately. By using this GANs model, 70% of the wind tunnel test cases can be saved, largely alleviating the cost of this kind of wind tunnel testing study.

Traffic pollution has posed a serious threat to the health of near-road city residents and pedestrians, especially in high-density cities. However, the influences of envelope features, including balconies, overhangs and wing walls, on pollutant exposure to near road residents and pedestrians have not been fully understood. This paper investigates the effects of three commonly-used envelope features on wind flow and pollutant exposure to residents in street canyon with three different aspect ratios. The evaluation metrics of personal intake fraction and daily pollutant exposure are used to quantitatively assess the influences caused by different envelope features on healthy risk of near-road residents and pedestrians, alongside with wind flow pattern and pollutant distribution. The results show that these envelope features have increased the risk of pollutant exposure for the leeward side residents, while the risk of pollutant exposure for the windward side residents is reduced for most cases, in particular for the first floor. This observation is especially prominent when the canyon has the highest aspect ratio among the tested ratios, with the increased ratio of personal intake fraction reaching up to 540%. Moreover, the pollutant concentration is overall higher on leeward side of upstream building than that of windward side of downstream building. These findings can help urban planners and architects to build healthy and sustainable urban environment.

Fire-driven flows associated with wind intervention can dangerously threaten buildings in bushfire-prone areas by increasing pressure load on the structures through fire-wind enhancement phenomenon. This phenomenon through which wind is enhanced by interacting with fire is exacerbated when the affected terrain is located in a positive slope area. This study employs LES simulations using FireFOAM platform to investigate the extent to which the wind enhanced by a point source of fire is affected by terrain slope. A module was appended to the FireFOAM solver to extract and output fire-induced forces and acceleration components for the analysis. The effects of terrain slope on wind velocity enhancement as well as the location at which local maximum wind enhancement occurs were studied. The LES results showed that with the increase of terrain upslope angle, wind enhancement along the centerline is significantly intensified, whereas local maximum wind enhancement that occurs at each side of the centerline is less affected. It was also shown that global maximum wind enhancement occurs immediately downstream of the fire source for all upslope angles. Moreover, similar to the local maximum wind enhancement, the rate of increase in global maximum wind enhancement reduces with the increase of terrain upslope angle. Keywords: Fire-wind enhancement, Point source fire, Terrain slope, Local and global maximum wind enhancement

Unraveling the physics of fire-wind interaction has long been a subject of interest. Among all the physics involved, enhancement of wind by fire deserves great attention due to its potential effects on building structures downstream of the fire source in bushfire attack events. Predominantly, two contributing factors determine the extent to which wind is enhanced by fire: freestream wind velocity and fire intensity. This study employs Large-Eddy Simulation (LES) to fundamentally investigate the combined effects of freestream wind velocity and fire intensity on fire-wind enhancement. An added module was implemented to an open-source transient fire solver in order to analyze the effects of freestream wind velocity and fire intensity based on the analysis of interactions between momentum and fire-induced buoyancy forces. Simulations are performed for parametric combinations of wind velocity and fire intensity. The LES results demonstrate that the normalized maximum wind enhancement increases with a reduction of freestream wind velocity and an increase in fire intensity. The non-dimensional Froude number, Fr, and normalized fire intensity, I*, were employed to quantify the effects of freestream wind velocity and fire intensity, respectively. A correlation was developed to determine the maximum wind enhancement as a function of Fr and I*. The location corresponding to maximum wind enhancement occurs further downstream of the fire source as freestream wind velocity or fire intensity increases. A correlation based on the Fr number and I* was developed for the location at which maximum wind enhancement occurs. Furthermore, the concept of wind enhancement plume line was defined as a line along which the local wind enhancement occurs at a given longitudinal location downstream of the fire source, for which a correlation was also developed. Moreover, a gradual decaying trend is observed in wind enhancement after reaching a peak along the wind enhancement plume line in all simulation scenarios for which a correlation was also developed as a function normalized longitudinal direction.

Numerous studies have been carried out to measure wind pressures around circular cylinders since the early 20th century due to its engineering significance. Consequently, a large amount of wind pressure data sets have accumulated, which presents an excellent opportunity for using machine learning (ML) techniques to train models to predict wind pressures around circular cylinders. Wind pressures around smooth circular cylinders are a function of mainly Reynolds number (Re), turbulence intensity (Ti) of the incident wind, and circumferential angle of the cylinder. Considering these three parameters as the inputs, this study trained two ML models to predict mean and fluctuating pressures respectively. Three machine learning algorithms including decision tree regressor, random forest, and gradient boosting regression trees (GBRT) were tested. The GBRT models exhibited the best performance for predicting both mean and fluctuating pressures, and they are capable of making accurate predictions for Re ranging from 104 to 106 and Ti ranging from 0% to 15%. It is believed that the GBRT models provide an efficient and economical alternative to traditional wind tunnel tests and computational fluid dynamic simulations for determining wind pressures around two-dimensional smooth circular cylinders within the studied Re and Ti range.

The non-wind-induced additional nonlinear damping and stiffness of a spring-suspension system (under wind-off conditions) would significantly influence the prediction of aeroelastic response. This study proposes a forced vibration technique to identify the non-wind-induced nonlinear damping and stiffness of both vertical and inclined prisms. The forced vibration-pressure test was performed to observe the non-wind-induced pressure at first. It was observed that the pressure was remarkably affected by the amplitude of structural oscillation, and the corresponding non-wind-induced force is thus nonlinear. A procedure is then proposed to identify the non-wind-induced nonlinear damping and stiffness of the prisms from the tested nonlinear forces. The results yielded by the proposed procedure in terms of a vertical prism has been verified by comparing the response predicted by the unsteady aerodynamic force with/without the non-wind-induced nonlinearities with the measured response. Moreover, the non-wind-induced nonlinearities of inclined prisms have been tested by using the proposed forced vibration technique, which also suggests a mathematical model of the identified results for the purpose of convenience.

We tested the hypothesis that random variations in the magnitude of sinusoidal linear acceleration cause greater modulation of skin sympathetic nerve activity (SSNA), but not muscle sympathetic nerve activity (MSNA), than sinusoidal stimuli of the same frequency but constant amplitude. Subjects (n = 22) were seated in a sealed room mounted on a linear motor that could deliver peak sinusoidal accelerations of 30 mG in the antero-posterior direction. Subjects sat on a padded chair with their neck and head supported vertically, thereby minimizing somatosensory cues, facing the direction of motion in the anterior direction. Each block of sinusoidal motion was delivered at 0.2 Hz, either with a constant-amplitude (root mean square 14 mG) or randomly fluctuating amplitudes of the same mean amplitude. MSNA (n = 12) and SSNA (n = 10) were recorded via tungsten microelectrodes inserted into muscle or cutaneous fascicles of the common peroneal nerve. Cross-correlation analysis was used to measure the magnitude of vestibular modulation. The modulation index for SSNA was significantly higher during delivery of random vs constant-amplitude acceleration (31.4 ± 1.9 vs 24.5 ± 2.5%), but there was no significant difference in the modulation indices for MSNA (28.8 ± 2.9 vs 33.4 ± 4.1%). We conclude that the pattern of vestibular stimulation affects the magnitude of modulation of sympathetic outflow to skin but not to muscle. Presumably, this is related to the subperceptual development of nausea, which is known to be associated with greater vestibular modulation of SSNA but not MSNA.

This study uses a longitudinal within-subjects design to investigate the effects of inadequate Indoor Environmental Quality (IEQ) on work performance and wellbeing in a sample of 114 office workers over a period of 8 months. Participants completed a total of 2261 online surveys measuring perceived thermal comfort, lighting comfort and noise annoyance, measures of work performance, and individual state factors underlying performance and wellbeing. Characterising inadequate aspects of IEQ as environmental stressors, these stress factors can significantly reduce self-reported work performance and objectively measured cognitive performance by between 2.4% and 5.8% in most situations, and by up to 14.8% in rare cases. Environmental stressors act indirectly on work performance by reducing state variables, motivation, tiredness, and distractibility, which support high-functioning work performance. Exposure to environmental stress appears to erode individuals' resilience, or ability to cope with additional task demands. These results indicate that environmental stress reduces not only the cognitive capacity for work, but the rate of work (i.e. by reducing motivation). Increasing the number of individual stress factors is associated with a near linear reduction in work performance indicating that environmental stress factors are additive, not multiplicative. Environmental stressors reduce occupant wellbeing (mood, headaches, and feeling 'off') causing indirect reductions in work performance. Improving IEQ will likely produce small but pervasive increases in productivity.

The aerodynamic mechanism of galloping of an inclined square cylinder was investigated using both experimental and numerical methods. Experimentally, pressure measurements on the inclined cylinder were taken in the wind tunnel. Numerically, a large eddy simulation was used to investigate the flow field around the cylinder. When the inclination is forward to the approaching wind, it significantly increases the curvature of the shear layer near the free end of the cylinder whereas decreases it near the base. Conversely, when the inclination is backward, it decreases the curvature near the free end while increases it near the base. The variation in the curvature has remarkably influenced the pressure distributions on the side faces and hence the transverse force coefficient, which governs the galloping behavior of the cylinder. The particular curvature of the shear layer in the forward inclination case is a consequence of an inverted V-shaped spanwise vorticity distribution, which is induced by an “extended tip vortex pair” with an inverted V-shaped streamwise vorticity distribution. However, in the backward inclination case, the shear layer curvature is attributable to a V-shaped spanwise vorticity distribution caused by an “extended base vortex pair” with a V-shaped streamwise vorticity distribution.

A new linear wind generator (LWG), named PowerWindow, is introduced. The modular and scalable LWG is capable of generating power in low wind velocity condition, and hence can be an effective and safe power generator in built environments. The aerodynamic mechanism of the LWG power generation is elucidated using computational fluid dynamic (CFD) simulations, and the results are validated against the experimental data obtained from the prototype wind tunnel tests. The simulations provide important insights into the flow field in and around LWG particularly over the front and rear blades and how each one contributes to the power generation. This study shows that PowerWindow can generate power with an acceptable coefficient of performance (CP≈0.15) in very low linear velocity ratio (λ≈0.2), which is not achievable in most conventional wind turbines at comparable size.

In this study, we used a computational fluid dynamics (CFD)–discrete element method (DEM) model to analyze the triggering of sand movement below an offshore pipeline. The advantage of this CFD–DEM model is that it considers the motion and force applied to every individual particle, thereby facilitating detailed simulations of seepage flow and the breakdown of the water–sand mixture beneath the pipeline. The simulation results were similar to previous experimental studies, which showed that scouring occurs after the driving pressure beneath the pipe generates a floating gradient in the sand layer near the wake. Furthermore, the computed critical current velocity that leads to the onset of scour was in reasonable agreement with the observational data. Thus, we consider that CFD–DEM is a promising numerical tool for future investigations of the mechanism that underlies the onset of scour.

The flow field around a rigid finite square cylinder inclined away from the vertical direction was numerically investigated via large eddy simulations. The cylinder under investigation had a height-to-width ratio of 18 and the inclination angle, defined as the angle between the cylinder orientation and the vertical direction, varied from forward inclination to backward inclination. Pressure measurements and flow visualizations were taken in a wind tunnel to validate the numerical simulations. The forward inclination is found to enhance the downwash, which is initially observed behind the free end of the vertical cylinder, and amplify it to a downward axial flow. Conversely, the backward inclination promotes upwash, which originates behind the base of the vertical cylinder, to be an upward axial flow. On the other hand, the vertical cylinder produces two pairs of counter-rotating streamwise vortices (quadrupole wake) in its wake, but only one pair of vortices (dipole wake) is observed to form behind both the forward and backward inclined cylinders. Moreover, only a free-end vortex pair is exhibited behind the forward inclined cylinder whereas a base vortex pair exists behind the backward inclined cylinder. They are considered to generate the downward and upward axial flow respectively. It is anticipated that the presence of the axial flow significantly influence both the pedestrian-level wind conditions and the aerodynamic characteristics of the cylinder.

This study investigated aerodynamic characteristics of an inclined square prism experimentally. Pressure measurements were performed on a static square prism with a series of inclinations including forward inclinations (inclined to the upwind direction) and backward inclinations (inclined to the downwind direction). The prism with a vertical attitude was also tested for comparisons. Based on the pressure data, influences of the inclinations on aerodynamic characteristics (e.g., force coefficients, pressure distributions on the surfaces, and vortex shedding features) of the square prism were evaluated in detail. The results show that the inclinations have significant effects on these aerodynamic characteristics. Furthermore, the influences of the forward and backward inclinations are quite different.

Low airflow or poor outdoor ventilation around building blocks can negatively influence pollutant dispersion in the surroundings and indoor air quality, and increase the risks of airborne transmission of infectious diseases. However, there have been few studies addressing the wind environment, thermal comfort and other concerns at the pedestrian level. Buildings with a lift-up design may have a number of impacts on the pedestrian-level wind and thermal environments. Three building configurations that resulted in the lowest wind speed zones were identified from a previous study. A 3.5 m high open ground floor was added to each of the three configurations, and scale models of the three designs were studied in a wind tunnel to assess their influences on airflow and ventilation around the buildings. Undesirable areas of low wind speed leading to poor air ventilation and, on the other side of extreme, areas of discomfort due to strong wind conditions were both identified, and their practical implications are discussed.

Residents wish to have outdoor spaces to enjoy walking, cycling, and other recreational activities, which are often hindered by the unfavorable thermal comfort conditions, especially in the summer. High building densities lower the average wind speed and this intensifies the urban heat island effects at city scale. The conscientious use of building morphology to create local thermal comfort zone at selected spots in a large precinct is becoming a pressing issue for sustainable urbanization. This paper is a proof of concept study via continuous monitoring of the pedestrian level winds and thermal parameters at two sample days in summer, which include instantaneous air temperature, globe temperature, wind speed and humidity. Three outdoor locations at an university campus are chosen and daytime thermal perceptions at the three sites were evaluated using PET (Physiological equivalent temperature). A PET based new index was defined, which is called the thermally-perceivable environmental parameter difference. By analyzing the simultaneous differences of radiant temperature, wind speed and air temperature between the monitored spots, it is shown that it was the wind speed and radiant temperature differences that were making significant differences in thermal comfort. This pilot study clearly indicates that wind amplification combined with shading effects can generate thermally comfortable conditions in the open ground floor beneath an elevated building, even on a sunny, hot summer day in a subtropical city. This finding helps to alert city planners of additional options available in precinct planning to encourage outdoor activities.

This study investigated the galloping behavior of a slender square-section cylinder inclined from the vertical direction by a series of angles. Both aeroelastic tests and pressure measurements were performed on the cylinder with forward inclinations (inclined to the upwind direction), a vertical attitude and backward inclinations (inclined to the downwind direction). Results from the aeroelastic tests show that the galloping amplitude of the cylinder decreases substantially with increasing the forward inclination angle. Unlike the forward inclination case, not all the backward inclined cylinders oscillate at an amplitude smaller than the vertical cylinder does. The galloping amplitude of the cylinder with a small backward inclination angle is significantly larger than that of the vertical cylinder, whereas the cylinder with a large backward inclination angle exhibits a lower amplitude. Comparing aeroelastic galloping amplitudes with those predicted by the quasi-steady theory shows that the quasi-steady theory is applicable to predict the variation trend of the galloping behavior induced by both forward and backward inclinations, although it is unable to give accurate predictions on galloping amplitudes of all the inclined cylinders.

A numerical wind tunnel model was proposed. The computed results of the pollutant diffusion around a typical Hong Kong high-rise building model (at a linear scale of 1:30), were found to show a similar trend to the outcomes of self-conducted experimental measurements that the pathways of pollutant migration for windward and leeward pollutant emission are different. For the case with windward pollutant emission at the 3rd floor within a re-entry, the pollutant migrated downwards due to the downwash created by the wind. In contrast, for the case with leeward pollution emission, dispersion is dominated by intense turbulent mixing in the near wake and characterized by the upward migration of the pollutant in the leeward re-entry. The simulated results of haze-fog (HF) studies confirm that the pathway of pollutant migration is dominated by wind–structure interaction and buoyancy effect only plays a minor role in the dispersion process., Graphical abstract, Highlights • A self-developed numerical wind tunnel model was proposed. • Characteristics of air pollutant dispersion with windward/leeward emission were discussed. • Wind–structure interaction controls the air pollutant dispersion around the building., The different characteristics of air pollutant dispersion around a high-rise building, for both cases of a dispersion source in either the windward face or leeward face, are dominated by wind–structure interaction, with buoyancy effect playing only a minor role.

This paper presents an integrated computational design optimization method for the performance-based design of tall buildings subjected to various levels of wind excitation. A performance-based wind engineering design framework is proposed by defining various performance objectives associated with multiple levels of wind hazards. A nonlinear static pushover analysis is employed to predict the inelastic drift performance of tall buildings subject to very rare extreme wind events. The optimal performance-based design problem considering inelastic deformation is formulated and solved by the augmented optimality criteria method. The effectiveness and practicality of the optimal wind-resistant performance-based design technique are illustrated by a practical 40-story residential building.

Flow-induced vibrations (FIV) of four identical circular cylinders placed in a square arrangement are numerically investigated. Modeled as a spring-damping system subjected to uniform flows, each cylinder is allowed to freely oscillate with equal natural frequencies in the inline and transverse directions. The spacing ratio, L / D , remains 5, where L is the central distance of any two adjacent cylinders and D the cylinder diameter. The Reynolds numbers are chosen as Re =80 and 160. The incidence angle of the incoming uniform flow is α =0°. The mass ratio for each cylinder is M r =6.0 and the reduce velocity, U r , varies from 3 to 14. The coupled system is numerically resolved by a semi-implicit characteristics-based split (CBS) finite element algorithm under the arbitrary Lagrangian–Eulerian description. The calculated results are analyzed in detail. In particular, some intrinsic mechanisms are interpreted on the cylinder responses and the wake patterns. The unsymmetrical figures of “8” and “O”, and other irregular figures are observed in the cylinders’ X – Y trajectories. Besides the “4S” wake pattern, the “2P+2S” pattern is discovered herein. The “dual-resonance” phenomenon, which indicates the cylinders’ synchronizations occurring in both the inline and transverse directions, is detected in this work.

[Abstract:] 2D URANS simulations are conducted aiming to study the aerodynamic performance under smooth flow of twin-box decks depending on the gap distance between girders. The Stonecutters Bridge is taken as the reference geometry. In this parametric study, 14 gap to depth ratios in the range 0 ≤ G/D ≤ 9.70 are investigated, and for each geometry, 11 angles of attack in the range −10 ◦ ≤ α ≤ 10 ◦ are considered. Specific goals of this research have been: identification of the fundamental flow features, study of mean and fluctuating pressure coefficients distributions, identification of the vortex shedding mechanisms and general aerodynamic characterisation based on force coefficients. The numerical results provided herein are validated with wind tunnel data previously reported in the literature, finding a good agreement. A critical gap to depth ratio at G/D = 2.35, in terms of aerodynamic response, was identified, which is consistent with the value reported in the literature for a different bridge based on wind tunnel tests. The obtained set of data provide a general picture of the expected aerodynamic performance of a twin-box deck depending on the gap distance and could be of great value at the early design stage of long-span cable-supported bridges. Ministerio de Economía y Competitividad; BIA2016-76656-R Ministerio de Economía y Competitividad; BES-2014-068418 Ministerio de Economía y Competitividad; BIA2013-41965-P Xunta de Galicia; ED431C 2017/72

This paper examines a new measure of the unsteady galloping force of a slender prism using a hybrid pressure-aeroelastic test (HPAT) technique. The HPAT was performed to simultaneously observe the unsteady crosswind force and response of a test model. The observed crosswind force contains amplitude-dependent non-windinduced aerodynamic force that was caused by the interaction between the oscillating test model and the surrounding air. The unsteady galloping force of the test model was therefore evaluated by removing the non-wind-induced aerodynamic force identified by using a forced vibration technique from the observed unsteady crosswind force. The amplitude-dependent mechanical nonlinearities (damping and stiffness) of the HPAT system were identified by using a wavelet method from a free decay response of the test model. By substituting the obtained unsteady galloping force and the mechanical nonlinearities into the governing equation of motion of the test model, the galloping responses of the test model were predicted. The results show that the galloping responses of the test model predicted by the identified unsteady galloping force are identical to the experimentally measured response, and

A mathematical model to quantify the unsteady self-excited forces (USEFs) acting on a slender prism was developed, to address the shortcomings of the classical quasi-steady theory employed to predict the galloping instability of slender prisms. The unsteady aerodynamic force and galloping response of a prism were measured from a hybrid aeroelastic-pressure balance (HAPB) that can synchronously observe unsteady pressure and aeroelastic response. It was found that the galloping response predicted by the unsteady aerodynamic force is in close agreement with the experimental result whereas the quasi-steady theory cannot predict the galloping instability. According to an energy equivalent method, the unsteady aerodynamic force was quantitatively decomposed into three components: an aerodynamic damping force component, an aerodynamic stiffness force component and a residual force (buffeting force) component. Subsequently, a nonlinear mathematical model for the USEF which is a 1st-order polynomial function representing the aerodynamic damping and stiffness force components, was established. The results indicated that the 1st-order model was effective in predicting the galloping response of the prism. It was also demonstrated that the model can be used to predict the galloping instability of prisms with different mass-damping ratios.

The current study uses a longitudinal within-subjects design to investigate the effects of wind-induced tall building motion on occupant wellbeing and work performance. 47 office workers on high floors of wind-sensitive buildings and 53 control participants completed 1909 surveys across 8 months and over a range of wind conditions. The results show that the effects of building motion are emergent, as motion sickness develops after a duration of exposure to motion, which mostly manifest as symptoms of sopite syndrome, or low-dose motion sickness (tiredness, low motivation, distraction from work activities, and low mood), which occur at 2–3 times baseline rates. As motion sickness increases, work performance significantly decreases by 0.76–0.90 standard deviations below baseline. Affected individuals attempt to manage their own discomfort, and indicate a preference to work a different location during motion, take 30–40% longer breaks, and attempt to self-medicate using analgesics. Humans are adaptable, allowing most occupants to continue their work activities, but at reduced levels of performance and comfort. Design criteria for tall buildings should attempt to minimise the environmental stress of building motion on work performance and wellbeing rather than motion tolerance or formal complaint to building owners.

Variation in flow characteristics triggered through the fire-wind interface can potentially damage the buildings during bushfires. Fire-wind enhancement which is referred to as the increase of wind velocity, caused by the fire-wind interaction, is one of the destructive phenomena in this regard. In spite of the significance, the underlying mechanism contributing to this phenomenon is still not well understood. This study employs computational fluid dynamic (CFD) simulation to fundamentally investigate the effects of free-stream wind velocity on fire-wind enhancement through analyzing the momentum and buoyancy of fluid. Fire-wind interaction is shown to cause the generation of fire-induced longitudinal negative pressure gradient which results in fire-induced pressure and viscous forces in longitudinal direction. These forces are further found as the prime reason for the distortion of the wind velocity profile. A module is implemented to the FireFOAM solver to calculate and extract these forces quantitatively. The results reveal that under a constant fire intensity, the level of distortion and/or enhancement in the wind velocity profile comparatively reduces with the increase of free-stream wind velocity. A new non-dimensional group (modified Euler number) is introduced to take into account dominant fire-induced forces causing fire-wind enhancement. Richardson number and the modified Euler number are employed to determine the influence of free-stream wind velocity and longitudinal distance from the fire source on wind velocity enhancement. Large-eddy simulation (LES) results indicate that while the level of enhancement generally depends on both Richardson and the modified Euler number, the location of the maximum level of enhancement along the plume centreline coincides with the maximum value of modified Euler number under a constant free-stream wind velocity scenario.

This study evaluated the performance of wind energy harvesters with multiple shape-optimized circular cylinders in tandem via computational fluid dynamics simulations. The circular cylinders were optimized by attaching triangular protrusions on their surface. The circumferential location of the protrusion plays a crucial role in the efficiency of this kind of wind energy harvester. The protrusions at the circumferential angles of α = 60°and 90°significantly extend the wind velocity range with remarkable energy generation. When the reduced wind velocity is lower than 10, the harvester with three plain cylinders in tandem generates the most power. However, when the speed is higher than 10, the most power is generated by the harvester having three cylinders in tandem with protrusions at α = 60°. Therefore, in a low wind velocity environment, the harvester with three plain circular cylinders in tandem is superior to other tested configurations, whereas in a high wind velocity environment, the harvester with three circular cylinders with protrusions at α = 60°in tandem outstands from other tested configurations. The associated flow mechanisms are detailed as well.

This study evaluated the performance of twin adjacent galloping-based piezoelectric wind energy harvesters based on mutual interference. The relative position between the twin harvesters is crucial to their energy generation efficiency. A series of wind tunnel tests were conducted to test energy generation of the two harvesters in tandem or staggered arrangements. The optimal relative position, a streamwise center to center spacing of 1.2B (B is the width of the harvester's square prism) and a transverse center to center spacing of 1.0B, was identified. The total output power of the two harvesters placed in the optimal relative position is up to 2.2 times that of two isolated harvesters. The output power is also much larger than that of the harvesters in tandem arrangements that have been widely tested in previous studies. Therefore, it is recommended to position two adjacent harvesters in optimal relative position(s) to deliver an optimal power output.

1014 central business district workers in Wellington, New Zealand, were surveyed about their experiences of wind-induced building motion, susceptibility to motion sickness, reported compensatory behaviours, and complaints about building motion. Overall, 41.7% of the respondents reported that they had felt wind-induced building motion, and 41.6% of those respondents reported perceptible motion at least once a month. Difficulty in concentrating was the most frequently reported effect of building motion, reported by 41.9% of the respondents who had felt building motion. This suggests that early onset motion sickness develops in many building occupants. Despite a strong preference to avoid working in tall buildings, highly susceptible individuals were equally likely to work on high floors as low floors, increasing their potential exposure to building motion. These highly susceptible individuals were more likely to report symptoms of motion sickness due to building motion. Despite the reported adverse effects of motion sickness, building occupants in general almost never make formal complaints about building motion, contradicting the widely held assumption that complaint is an effective index of building performance. Some building occupants then actively compensate for the effects of building motion by taking more breaks and in some cases taking motion sickness tablets. Implications for occupant comfort, motion sickness, the rate of occupant complaint and compensatory behaviours are discussed.

The surge in population and the diversification of global economic and financial influences has generated unprecedented demands for office and residential high-rise developments in the past decade. The dynamic responses of wind-sensitive buildings inevitably challenge the understanding of subjective human response to building motion. Significant building sway during strong winds, typhoons (or hurricanes) and monsoons may potentially have an adverse affect on the well-being and comfort of the occupants who live and/or work within these skyscrapers. Some building occupants react by feeling unwell (suffering seasickness-like symptoms), some may react with fear (leaving them with a disconcerting feeling about the structural integrity of the building), while the equanimity of others may be adversely affected. This paper summarises the development of prediction equations using logistic regression techniques, based upon exploratory analyses of factors, including cultural influences, as well as empirical results from two motion simulator experiments, with the aims of predicting the possible behaviour of building occupants.

Re-ingestion of the contaminated exhaust air from the same building is a concern in high-rise residential buildings, and can be serious depending on wind conditions and contaminant source locations. In this paper, we aim to assess the prediction accuracy of three k-ɛ turbulence models, in numerically simulating the wind-induced pressure and indoor-originated air pollutant dispersion around a complex-shaped high-rise building, by comparing with our earlier wind tunnel test results. The building modeled is a typical, 33-story tower-like building consisting of 8-household units on each floor, and 4 semi-open, vertical re-entrant spaces are formed, with opposite household units facing each other in very close proximity. It was found that the predicted surface pressure distributions by the two revised k-ɛ models, namely the renormalized and realizable k-ɛ models agree reasonably with experimental data. However, with regard to the vertical pollutant concentration distribution in the windward re-entrance space, obvious differences were found between the three turbulence models, and the simulation result using the realizable k-ɛ model agreed the best with the experiment. On the other hand, with regard to the vertical pollutant concentration distribution in the re-entrant space oblique to the wind, all the three models gave acceptable predictions at the concentration level above the source location, but severely underestimated the downward dispersion. The effects of modifying the value of the turbulent Schmidt number in the realizable k-ɛ model were also examined for oblique-wind case. It was confirmed that the numerical results, especially the downward dispersion, are quite sensitive to the value of turbulent Schmidt number.

The association of bushfires with wind has long been recognised, but the mechanism of this interaction has not received due attention. In the current study, a computational fluid dynamics approach was used to reveal the impact of fire-enhanced wind on low-rise building structures. This paper presents the results of a numerical study on bushfire, wind and structure interactions. The fire-enhanced wind was found to significantly distort the wind velocity profile and enhance turbulence properties, and alter the pressure coefficient distributions around a simple building structure represented by a 6 m cube. In particular, the simulated results revealed a significant increase in windward wall pressure coefficient due to the presence of a fire source upstream compared to that without fire. These findings are expected to have a significant impact on the development of improved design practice for the protection of buildings from fire-induced wind storms.

The effects of gap-width on the aerodynamic characteristics of a twin-deck bridge in a nominally smooth flow were investigated in this paper, with a specific goal of studying the vortex shedding mechanisms of the bridge deck. Simultaneous pressure measurements were carried out on five deck configurations, using a rigid sectional model of a twin-deck cable-stayed bridge with different gap-widths. Stream-wise mean and fluctuating pressure distributions around the bridge deck were studied to investigate the potential excitation mechanisms caused by the gap-widths at various angles of wind incidence. The effects of gap-width on the static force and moment coefficients were also analyzed. The results demonstrated that the gap-width has the potential to significantly affect the pressure distribution and hence the corresponding aerodynamic performance of the bridge deck. In addition, the analyzed results showed that the twin-deck bridge in this study is susceptible to vortex shedding and its Strouhal number gradually increases with increasing gap-width due to the change of flow regime around the bridge deck. This knowledge is essential for the complete aerodynamic evaluation of a twin-deck bridge.

We have previously shown that sinusoidal galvanic vestibular stimulation, a means of selectively modulating vestibular afferent activity, can cause partial entrainment of sympathetic outflow to muscle and skin in human subjects. However, it influences the firing of afferents from the entire vestibular apparatus, including the semicircular canals. Here, we tested the hypothesis that selective stimulation of one set of otolithic organs-those located in the utricle, which are sensitive to displacement in the horizontal axis-could entrain sympathetic nerve activity. Skin sympathetic nerve activity (SSNA) was recorded via tungsten microelectrodes inserted into cutaneous fascicles of the common peroneal nerve in 10 awake subjects, seated (head vertical, eyes closed) on a motorised platform. Slow sinusoidal accelerations-decelerations (~4 mG) were applied in the X (antero-posterior) or Y (medio-lateral) direction at 0.08 Hz; composite movements in both directions were also applied. Subjects either reported feeling a vague sense of movement (with no sense of direction) or no movement at all. Nevertheless, cross-correlation analysis revealed a marked entrainment of SSNA for all types of movements: vestibular modulation was 97 ± 3 % for movements in the X axis and 91 ± 5 % for displacements in the Y axis. For each sinusoidal cycle, there were two major peaks of modulation-one associated with acceleration as the platform moved forward or to the side, and one associated with acceleration in the opposite direction. We interpret these observations as reflecting inertial displacement of the stereocilia within the utricle during acceleration, which causes a robust vestibulosympathetic reflex.

The implementation of a vibration control system has always been associated with considerable capital and long-standing main- tenance costs, resulting in limited practical applications of damping devices. The notion of a massive implementation cost is largely the result of a lack of cost analysis of vibration control systems in the literature. This paper presents the structural design of awind-sensitive tall building at various design stages and the results of a collaborative study with two damper construction companies on the cost estimation of a control device. A series of wind tunnel pressure tests were conducted on a 1∶400 scale model to determine the translational and torsional wind forces acting on the studied building. A structural optimization was subsequently employed to reduce the excessive top deflection, and a smart tuned mass damper was implemented at the final design stage to meet occupant comfort criteria. The details of each structural design stage, the implementation of vibration control devices, and a collaborative study on damper cost are outlined in this paper. DOI: 10.1061/(ASCE)ST .1943-541X.0000486. © 2012 American Society of Civil Engineers. CE Database subject headings: Torsion; Damping; High-rise buildings; Wind forces; Costs. Author keywords: Lateral-torsional motion; Structural optimization; STMD; Damper pricing chart.

It is well known that high-rise buildings affect the surrounding pedestrian level wind environment. In recent years, awareness and concern has increased about the creation of low wind speed areas around tall buildings which may lead to poor out-door air ventilation. In addition, new building developments are often not restricted to a single building, but comprise a row of buildings, which may have complex plan-forms, and some integrating an extensive podium. This paper aims at providing a fundamental understanding of wind–structure interactions that govern the effects of building dimensions and separations, a row of buildings and podium on the pedestrian level wind environment, for both weak and strong wind conditions, by a series of parametric wind tunnel studies. The study area covered an extensive area which covered up to 400 m downstream of the test buildings. The results show that a single wider building created adverse effects on the natural air ventilation at pedestrian level around the building while a taller building improved the near-field air ventilation conditions. In the studies of building separation effects, the results show an adverse effect on natural air ventilation at pedestrian level when the building separations are less than half the building width. Inclusion of a podium was also found to adversely affect the air movement around 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.

Field measurement techniques, including ambient wind excitation, crane excitation, synchronised human excitation and mechanical shaker methods, commonly employed to measure the dynamic properties of high-rise buildings are presented. The instrumentation, test methodology, merits and limitations of these techniques, including a purpose-built computer-based mechanical shaker, are discussed. The dynamic properties of four residential buildings in Hong Kong ranging in height from 130 m to 256 m were determined using these field measurement techniques. The results show that the dynamic properties, including natural frequencies of vibration, damping values, and deflected mode shapes can be accurately determined. These measured dynamic properties are compared with values suggested by wind load standards, empirical predictors and computed values from finite element models. The measured natural frequencies were found to be in good agreement with the Japanese empirical predictor of 67 divided by building height, attributable in part to the design requirements in both regions to resist typhoon loading.

While there are a number of guidelines used throughout the world in the assessment of acceptability of tall building accelerations, none are based on systematically conducted surveys of occupant reaction to wind-induced motion. In this study, occupant response data were gathered by both a self-reporting mechanism and by interviewer-conducted surveys in control tower structures over a period of four years. These two approaches were designed in conjunction with experimental psychologists to ensure unbiased reporting. The data allowed analysis of perception thresholds and tolerability at different building frequencies and in different wind climates. The long-term nature of the studies also allowed an investigation of the causes and effects of adaptation to building motion. As the surveys were designed to allow multiple use during single storms, the effects of exposure duration were investigated. A final exit survey was conducted at the primary survey location to investigate views of the acceptability of windinduced motion and the factors underlying these views. The findings of the field studies indicate that none of the currently used acceleration guidelines address all of the factors that contribute to occupant dissatisfaction. An alternative framework for assessing acceleration acceptability is proposed.