Wind Load Reduction Research Articles

Heliostat Consortium: Gap Analysis on State of the Art in Wind Load Design

Abstract Wind loads are a major driver of heliostat cost. Standardized methods and tools are needed for a more detailed understanding of the static and dynamic loads of a heliostat design. This will enable cost reduction of wind-dependent heliostats to avoid unnecessarily conservative heliostat designs and increase field efficiency and reliability to reduce the risk of component failures due to high-wind events. Gaps related to wind load include lack of site characterization for wind measurements, insufficient critical load cases for heliostat design, insufficient understanding of turbulence impacts on heliostat tracking error, lack of knowledge on wind load under various heliostat array configurations, and underexplored heliostat field wind-load reduction and operating strategies. Recommended pathway forward is to develop wind load and site characterization guidelines for heliostat design and develop heliostat field wind-load models with optical performance impacts.

Influence of reduced drag load on stay cables on the construction cost of cable-stayed bridges: Two study cases

Rain–wind–induced vibrations (RWIVs) can cause the large-amplitude vibration of flexible cables in cable-stayed bridges; such vibration is one of the engineering safety problems that must be resolved. Currently, aerodynamic measures, such as dimples and spirals, are typically used as measures for suppressing vibration in stay cables. By calculating and comparing the equivalent static wind loads (ESWLs) of six typical cable-stayed bridges, the proportion of ESWL acting on the cable to that acting on the entire bridge increases approximately linearly with the bridge span. Hydrophobic coating can effectively suppress RWIVs and evidently relieve the ESWL. Hence, compared with the commonly used aerodynamic measures with surface roughness, this coating has a considerable potential as an alternative for suppressing vibration. Based on the foregoing, the wind resistance design optimization of two actual cable-stayed bridges with main spans of 420 and 1160 m is implemented to investigate the construction costs of cable wind load reduction. After optimization, the structural responses of the main towers are reduced by 4%–12%, and the optimized tower and foundation sizes are reduced by 5%–8%. The optimization for the two bridges exceed 5% and 7%, respectively. The construction investment savings are approximately 2.3 million and 7.2 million USD, respectively. These values further improve with increasing bridge span and design wind speed.

Wind Load Effect Study on Large-Aperture Parabolic Trough Collector Mirror Fields

Abstract Large-aperture parabolic trough collectors (LPTCs) are recognized as one of the most promising next-generation linear-focus concentrating solar power (CSP) technologies. However, large apertures inevitably introduce higher wind loads and stronger inter-row interactions. In the present study, a multi-physics-coupled model is established to study the wind load effect on multiple rows of LPTCs. First, it is found that wind load fluctuates significantly in the first four rows and then decreases gradually. The first and second rows suffer the most and least damage, respectively. Because wind load effect is highly dependent on the row number, it is recommended to build wind fences and reinforce the strength of collectors according to their positions in the solar field. Second, the wind load reduction effectiveness of the varied focal length design, incorporated in the LPTC, is numerically validated so that the stress and optical efficiency loss can be reduced by 29.1% and 58.9%, respectively. Finally, the optical efficiency loss is first introduced to evaluate the wind load reduction performance of different mirror gap sizes. The optimal mirror gap size is found to be dependent on the weight coefficient between the wind load reduction and the optical efficiency, which should be determined by the actual scenario. For weight coefficients of 1:1, 1:2, and 2:1, optimal mirror gap sizes of 90 mm, 30 mm, and 120 mm, respectively, are recommended for reference.

An effective two-stage optimization method on aerodynamic measures to mitigate wind loads considering uncertainties in wind direction and velocity

At present, deterministic optimization methods on aerodynamic measures are usually employed to mitigate wind loads at one certain wind direction, ignoring the effects of the uncertainties in wind direction and velocity on wind loads. The uncertain optimization method with the consideration of the joint probability distribution (JPD) of wind speed and direction is hardly to conduct because it is very time-consuming and costly. In order to overcome these shortcomings, this study proposes an effective two-stage uncertain optimization method considering uncertainties in wind direction and velocity to achieve a considerable reduction of wind loads. In the first stage, the exceedance probability distribution of wind loads is determined based on the JPD and the wind load coefficients on the building, and the wind loads in the most unfavorable range of wind directions are chosen as the optimization objective. In the second stage, the optimal values of the design variables are determined by an interval optimization algorithm using the surrogate model and non-dominated sorting genetic algorithm II in the most unfavorable range of wind directions, where the surrogate model is constructed by the radial basis function method to relate the wind load coefficients to the design variables of aerodynamic measures, and can significantly improve the efficiency of the optimization algorithm. To validate the effectiveness of the proposed method, a flat-roof building with four spoilers is investigated and the rotation angles of spoilers are set as the design variables. The results show that the proposed method reduces the uplift wind loads with a 50-years return period up to 15.48% compared to the deterministic optimization method for one certain wind direction.

A feasibility study on the application of mesh grids for heliostat wind load reduction

This study examines the effectiveness of mesh grids in heliostat field perimeter fences and edge-mounted devices for heliostat wind load reduction. Two experimental studies were conducted: (1) the effect of mesh porosity and non-dimensional longitudinal distance of a perimeter fence upstream on the forces on a heliostat, and (2) the effect of mesh porosity and non-dimensional height-chord ratio of a heliostat edge-mounted mesh device on the heliostat loads. The experiments were conducted using an instrumented heliostat model positioned in the atmospheric test section of the Adelaide Wind Tunnel. It was found that perimeter mesh fences reduce peak loads by up to 50% and edge-mounted porous mesh devices reduce peak loads by up to 30% at the expense of increasing loads at different elevation angles. The porosity and height-chord ratio of an edge-mounted mesh were found to be important parameters influencing the maximum drag and lift reductions in operating and stow positions. The results of this work show the potential of mesh grids for reducing wind load on heliostats, and the importance of conducting a detailed techno-economic analysis on mesh grids throughout a heliostat field. The application of mesh grids on commercial-scale heliostats requires a further evaluation of the reduction of heliostat wind loads and thus cost of a field through mitigation of the incoming ABL turbulence and wake-induced turbulence from upstream heliostats.

Wind Loading of Photovoltaic Panels Installed on Hip Roofs of Rectangular and L-Shaped Low-Rise Buildings

Many residential houses in Japan have hip roofs with pitches ranging from 20° to 30°. Recently, roof-mounted photovoltaic (PV) panels have become popular all over the world for environmental conservation. The design of PV systems in Japan is usually based on the Japanese Industrial Standard (JIS) C 8955 (2017). However, the standard does not provide wind force coefficients for PV panels installed near roof edges (up to 0.3 m from the edge) because flow separation at the roof edges causes large up-lift forces on such panels. In this paper, we investigated the wind force coefficients for designing PV panels installed on hip roofs of rectangular and L-shaped low-rise buildings. The roof pitch was set to 25° as a typical value. Rectangular panels were installed almost over the whole roof, including the edge zones. Because the thickness of PV panels and the distance between PV panels and the roof are both as small as several centimeters, it is difficult to make wind tunnel models of PV systems with the same geometric scale as that for buildings. We focused on a numerical simulation using the unsteady Bernoulli equation to estimate the pressures in the space between PV panels and the roof. In the simulation, we used the time histories of wind pressure coefficients on the bare roof, which were measured in a turbulent boundary layer. We propose installing PV panels with small gaps between them along their short sides. The gaps may reduce the wind loads not only on the PV panels but also on the roofing due to pressure equalization. We discuss the optimum gap width from the viewpoint of wind load reduction.

A Highly Efficient Multifunctional Wind Barrier Based on PVDF for Power Generation in the Qinghai–Tibet Railway

The Qinghai–Tibet railway is the highest altitude railway globally, and monitoring and maintenance are essential parameters to obtain dynamic structural and environmental information in dangerous areas. Wind barriers are usually used to protect the safe operation of trains at high wind speeds. The power supply for monitoring gadgets is an urgent problem for high hill areas. This article presents a novel and renewable wind barrier for harvesting wind energy. The system architecture includes four main components: 1) the crosswind input module, 2) the vortex shedding occurrence module, 3) the power generation module, and 4) the energy storage and wind load reduction module. Based on the experiments, under the maximum critical wind speed (17 m s−1), the 13.607 V open‐circuit voltage is recorded in a single wind barrier unit with a maximum power of 31.47 μW. The output power is sufficient for charging a 47 μF capacitor to 2.21 V within 50 s. The practicability of the proposed wind barrier for harvesting wind energy is proposed for renewable energy in the Qinghai–Tibet railway.

Reduction of wind loads on rectangular tall buildings with different taper ratios

To explore the influence of different taper ratios on wind loads reduction on rectangular tall buildings, the CAARC standard tall building model is selected as the benchmark model and four other rigid models with different taper ratios ranging from 5% to 20% are tested for pressure measurement in a boundary layer wind tunnel. Based on the test results, the distribution of wind pressure coefficients, local wind force coefficients, base moment coefficients and their power spectral densities from the five models are compared and discussed. Moreover, correlation factors for base moment coefficients and their power spectral densities concerning the effects of different taper ratios are provided. It has been proved that the aerodynamic performance of the rectangular tall building has been improved by the increasing of taper ratio. This study aims to provide useful information for the wind-resistant design of rectangular tall buildings.

Aerodynamic modifications for reduction of wind loads oncross plan shaped tall building

Corner modification plays an essential role in the reduction of the wind load and responses on tall buildings. The present study investigates the effectiveness of different corner modifications (chamfered, rounded, and recessed corners) to reduce the wind load on regular cross plan shaped tall buildings using the computation fluid dynamics technique. Here, ANSYS CFX is used to simulate the boundary layer wind environment around the building and compared with experimental results. The numerically simulated data are compared with some previous wind tunnel test data on the '+' plan building. Based on the numerical study, flow pattern near the corner regions, pressure contour, the variation of pressure coefficient along the periphery of the building, force and moment coefficients for three corner modified models are analyzed and compared with sharp edged cross plan shaped model to comprehend the extent of nonconformities due to corner modifications. The rounded corner modification is most effective in suppressing the wind load compared to chamfered and recessed corners. For rounded corners with 50% corner cut, the reduction in force and moment coefficients is substantial, with up to 26.26% and 28.58%, respectively, compared to sharp edged corners. A sudden shoot up in the negative Cp values near edges of the corner modified model, should require special attention in the design of cladding components. This paper led to comprehend the wind-induced responses of cross plan shaped building with various corner configurations.

Wire mesh fences for manipulation of turbulence energy spectrum

Manipulation of turbulence within an atmospheric boundary layer flow by application of woven wire mesh fences is investigated. Turbulence properties behind fences of different porosities and mesh opening widths were determined from velocity measurements in a wind tunnel. It is found that with the application of a fence with a porosity of 0.46, the streamwise turbulence intensity can be reduced from the inflow level of 12.5%–8.8% and the integral length scale can be reduced from 380 to 270 mm. The results show that behind the mesh fences turbulence kinetic energy decays as a power law function of the downstream distance for all wire mesh fences tested in the wind tunnel. The decay rate of turbulence kinetic energy is faster, and a larger reduction in the integral length scale is achieved for fences with porosities between 0.46 and 0.64 compared to higher porosities of between 0.73 and 0.75. Porosity of the woven wire meshes is found to be the key parameter which influences their turbulence reduction performance. In the end, application of the wire mesh fences for reduction of wind loads on solar panels and heliostats is discussed. Evaluation of wind loads based on the reduction of turbulence intensity and integral length scale shows that up to 48% and 53% reduction in peak drag and lift forces on a heliostat, respectively, can be achieved with application of mesh fences.

Wind load reduction effects on inner buildings by exterior porous façades

Modern architects often adopt the use of façades on new buildings or to improve the appearance of an existing old building. Among various types of facades, ones with porous skins are increasingly popular. The porous features can not only improve the aesthetic of design but can also significantly lower wind loads on the inner building. This research investigates the filtering performance of various exterior porous façades on the surface pressures of an ordinary building based on systematical wind tunnel tests. Three target parameters, the porosity percentage of the façade, the gap distance between the façade and the building surface, and the opening shape of the pores, are investigated in this study. Preliminary results show that the Reynolds number makes little difference to the measured mean and root-mean-square values of fluctuating pressures. Subsequent results show that the façade skin porosity and gap distance together contribute to any amplification or reduction of surface pressures measured on the inner building. Different reduction or amplification levels are also found highly related to the upstream or downstream region over the side faces for the mean and the fluctuating pressures. For a limited area near the building corners, an amplification in negative local pressures was found due to the flow entering the façade cavity on the windward face and being channeled between the façade and sidewall of the building. A channel-effect phenomenon is also indicated with the presence of the exterior skin in certain regions, instead of just the reducing effect from the pores.

Experimental study on wind load characteristics of high‐rise buildings with opening

SummaryFor investigation of the wind load characteristics on high‐rise buildings with opening, a series of rigid rectangular high‐rise building models with opening were tested by synchronous multi‐pressure sensing system (SMPSS) in a boundary wind tunnel. Influence parameters including different opening heights, opening rates, opening patterns, and terrain categories are studied in detail. Based on the test results, the local wind force coefficients, base moment coefficients, and power spectral densities were discussed. The results indicated that the opening could affect the wind loads acting on high‐rise buildings to different extent. The distinct reduction of wind loads on high‐rise buildings was found at along‐wind direction, which could be evaluated by a proposed simplified expression accordingly. This study aims to provide useful information for the wind‐resistant design of high‐rise buildings with opening.

Effect of corner modifications on 'Y' plan shaped tall building under wind load

Wind load and responses are the major factors which govern the design norms of tall buildings. Corner modification is one of the most commonly used minor shape modification measure which significantly reduces the wind load and responses. This study presents a comparison of wind load and pressure distribution on different corner modified (chamfered and rounded) Y plan shaped buildings. The numerical study is done by ANSYS CFX. Two turbulence models, k-epsilon and Shear Stress Transport (SST), are used in the simulation of the building and the data are compared with the previous experimental results in a similar flow condition. The variation of the flow patterns, distribution of pressure over the surfaces, force and moment coefficients are evaluated and the results are represented graphically to understand the extent of nonconformities due to corner modifications. Rounded corner shape is proving out to be more efficient in comparing to chamfered corner for wind load reduction. The maximum reduction in the maximum force and moment coefficient is about 21.1 % and 19.2 % for 50% rounded corner cut.

Wind loads and their reduction on mesh fabrics

The presented contribution deals with evaluation of wind loads on various layouts of plastic and steel mesh fabric. To obtain real wind effects and loads, the experimental measurement in the Boundary Layer Wind Tunnel (BLWT) in Bratislava has been prepared. The goal of an investigation is the determination of wind loads on permeable materials – plastic and steel fabric, using wind load reduction factor k. The mean wind pressure on the permeable material is obtained by multiplying the wind pressure to the impermeable surface by the reduction factor k depending on the Reynolds number. The experimentally determined reduction factor can be applied for design of the safety mesh fabric. Wind loads were obtained from measurement of wind velocity by Hot-Wire anemometry (HWA).

Aerodynamic treatments for reduction of wind loads on high-rise buildings

For investigation of the effects of building corner modifications on reduction of wind loads on high-rise buildings, a benchmark square model and three corner modified models including recessed, chamfered and rounded are tested by pressure measurements in a boundary layer wind tunnel. Based on the experimental results, mean wind pressure coefficients, base moment coefficients, local wind force coefficients, power spectral densities and vertical correlation coefficients of the three corner modified models are discussed and compared with those of the square model to provide comprehensive evaluations of the effects of the aerodynamic treatments on reductions of the wind loads. This paper aims to provide useful information for the wind-resistant design of high-rise buildings.

Retraction: Lin, J., Montpellier, P., and Tillman, C. (2011). “Aerodynamic Edge Devices for Reduction of Wind Loads on Roofs.” Nat. Hazards Rev. , 10.1061/(ASCE)NH.1527-6996.0000049 (Feb. 4, 2011)

Retraction: Lin, J., Montpellier, P., and Tillman, C. (2011). “Aerodynamic Edge Devices for Reduction of Wind Loads on Roofs.” <i>Nat. Hazards Rev.</i> , 10.1061/(ASCE)NH.1527-6996.0000049 (Feb. 4, 2011)

Wind Load Reduction in Hollow Panel Arrayed Set

Reducing the wind loading of photovoltaic structures is crucial for their structural stability. In this study, two solar panel arrayed sets were numerically tested for load reduction purposes. All panel surface areas of the arrayed set are exposed to the wind similarly. The first set was comprised of conventional panels. The second one was fitted with square holes located right at the gravity center of each panel. Wind flow analysis on standalone arrayed set of panels at fixed inclination was carried out to calculate the wind loads at various flow velocities and directions. The panels which included holes reduced the velocity in the downwind flow region and extended the low velocity flow region when compared to the nonhole panels. The loading reduction, in the arrayed set of panels with holes ranged from 0.8% to 12.53%. The maximum load reduction occurred at 6.0 m/s upwind velocity and 120.0° approach angle. At 30.00 approach angle, wind load increased but marginally. Current research work findings suggest that the panel holes greatly affect the flow pattern and subsequently the wind load reduction. The computational analysis indicates that it is possible to considerably reduce the wind loading using panels with holes.

Optimization Design of Damping Devices for a Super-Tall Building Using Computational Platform

본 연구에서는 파라매트릭 모델링 기법을 통해 다양한 대안을 고려할 수 있도록 개발된 StrAuto(이하 전산플랫폼)을 이용하여 감쇠장치에 따른 감쇠비 증가 효과와 풍하중 저감효과를 평가하였다. 비정형 초고층구조물의 수많은 구조시스템 대안 선정을 지원하는 전산플랫폼은 설계자 또는 엔지니어에게 초기 대안을 결정하는데 있어 유용한 도구가 된다. 감쇠장치의 용량 및 추가 요구감쇠비의 크기를 산정하는 과정에서 중요한 원 구조물의 감쇠비에 대한 추정은 풍하중에 대한 실계측 자료를 기반으로 수행된 국내외 관련 연구의 결과를 사용하였다. 감쇠장치는 층간 설치형 수동형 감쇠장치와 질량형 능동형 감쇠장치 두 가지 유형을 고려하였다. 감쇠장치에 의해 추가되는 감쇠비는 FEMA에서 제안한 식을 이용하여 등가 정적 해석을 수행하여 산정하였다. 전산 플랫폼 내부에 감쇠장치의 용량을 최적화하는 알고리즘을 내장함으로써 최적의 감쇠장치 설계안을 자동적으로 도출할 수 있다. 감쇠장치 설치에 따른 물량저감 효과는 풍하중 저감계수로 평가될 수 있으며, 455m 높이의 초고층구조물을 대상으로 제안한 방법의 유효성을 검증하였다. 제안한 방법을 사용하여 비선형 시간이력 해석을 통해 얻어진 지붕층 변위와 층별 전단력을 근사적으로 추정할 수 있음을 확인하였다.In the study, the effects of damping devices on damping ratio increase and wind-load reduction were investigated based on the computational platform, which is one of the parametric modeling methods. The computational platform helps the designers or engineers to evaluate the efficacy of the numerous alternative structural systems for irregular Super-Tall building, which is crucial in determining the capacity and the number of the supplemental damping devices for adding the required damping ratios to the building. The inherent damping ratio was estimated based on the related domestic and foreign researches conducted by using real wind-load records. Two types of damping devices were considered: One is inter-story installation type passive control devices and the other is mass type active control devices. The supplemental damping ratio due to the damping devices was calculated by means of equivalent static analysis using an equation suggested by FEMA. The optimal design of the damping devices was conducted by using the computational platform. The structural element quantity reduction effect resulting from the installation of the damping devices could be simply assessed by proposing a wind-load reduction factor, and the effectiveness of the proposed method was verified by a numerical example of a 455m high-rise building. The comparison between roof displacement and the story shear forces by the nonlinear time history analysis and the proposed method indicated that the proposed method could simply but approximately estimate the effects of the supplemental damping devices on the roof displacement and the member force reduction.

단방향 FSI 해석을 이용한 초고층 건축물의 풍하중 저감형 형상 최적화 - 모서리 형상변화를 중심으로 -

In consideration of the aerodynamic characteristics of the wind, the shape of the building is in a very close relationship with the wind problems. We know through preceding studies that large negative pressure is generated in the corner of the side face of the building, thus modified corner is effective in reducing the wind load. Preceding studies were performed in wind tunnel test. On the other hand, we figure out the behavior characteristics of the building by the wind through the numerical analysis simulation. Study models with certain height were carried out by applying modified corner. We compare the analytical and experimental results of various modified corners model and find the most optimized shapes of corner on wind load reduction. Finally, we prove to optimize the shape of the actual building by applying 1-way FSI analysis.

Development of a Soundproof System with Wind Load Reduction Mechanism for Railway Viaducts

Development of a Soundproof System with Wind Load Reduction Mechanism for Railway Viaducts