Static Wind Loads Research Articles

Wind-Induced Responses and Wind Loads on a Super High-Rise Building with Various Cross-Sections and High Side Ratio—A Case Study

With the development of construction technology and material, more and more super high-rise buildings will be constructed in the future. In a specific metropolitan area, super high-rise building with various cross-section and high side ratio have to been designed and constructed due to the size limitation of construction site. This kind of building is also very prone to wind excitations. In this research, wind tunnel tests for a practical case of this kind of building with surrounding buildings were carried out in atmospheric boundary wind tunnel. Equivalent static wind loads (ESWLs), wind-induced responses and wind load distribution on the building were analyzed. In particular, the base overturning moment along the axis with weak lateral stiffness were investigated for bearing capacity limit state design of the building. The results demonstrate that the maximum value of wind-induced base overturning moments and acceleration responses appears at 60° or 330° wind directions instead of the orthogonal wind direction, and the aerodynamic interference of surrounding buildings affects the wind pressure distribution on facades of the building. These results and conclusion may be helpful to wind-resistant design of super high-rise buildings with high side ratio.

Actuator fault tolerant offshore wind turbine load mitigation control

Offshore wind turbine (OWT) rotors have large diameters with flexible blade structures which are subject to asymmetrical loads caused by blade flapping and turbulent or unsteady wind flow. Rotor imbalance inevitably leads to enhanced fatigue of blade rotor hub and tower structures. Hence, to enhance the life of the OWT and maintain good power conversion the unbalanced loading requires a reliable mitigation strategy, typically using a combination of Individual Pitch Control (IPC) and Collective Pitch Control (CPC). Increased pitch motion resulting from IPC activity can increase the possibility of pitch actuator faults and the resulting load imbalance results in loss of power and enhanced fatigue. This has accelerated the emergence of new research areas combining IPC with the fault tolerant control (FTC)-based fault compensation, a so-called FTC and IPC “co-design” system. A related research challenge is the clear need to enhance the robustness of the FTC IPC “co-design” to some dynamic uncertainty and unwanted disturbance. In this work a Bayesian optimization-based pitch controller using Proportional–Integral (PI) control is proposed to improve pitch control robustness. This is achieved using a systematic search for optimal controller coefficients by evaluating a Gaussian process model between the designed objective function and the coefficients. The pitch actuator faults are estimated and compensated using a robust unknown input observer (UIO)-based FTC scheme. The robustness and effectiveness of this “co-design” scheme are verified using Monte Carlo simulations applied to the 5MW NREL FAST WT benchmark system. The results show clearly (a) the effectiveness of the load mitigation control for a wide range of wind loading conditions, (b) the effect of actuator faults on the load mitigation performance and (c) the recovery to normal load mitigation, subject to FTC action.

Static Wind Reliability Analysis of Long-Span Highway Cable-Stayed Bridge in Service

Long-span cable-stayed bridge is a typical wind-sensitive structure because of its light weight and great flexibility. The reliability evaluation of the cable-stayed bridge under wind action becomes a key issue during bridge design and operation. In this paper, taking Xiangshan Harbor highway cable-stayed bridge in Ningbo City in China as the engineering background, ANSYS 15.0 is used to build a finite element model of this bridge to explore its aerostatic stability and influencing parameters, then the static wind reliability of this bridge is analyzed. Firstly, considering the structural nonlinearity and the nonlinearity of static wind load comprehensively, the critical wind speed of aerostatic instability of the Xiangshan Harbor cable-stayed bridge is calculated by the internal and external double iteration method. Then the influence of the initial wind attack angle, steel wire breakage rate of the stay cables, static three-component force coefficients, and cable broken position on the static wind stability of this bridge are discussed. Thus, the variation rule of the critical aerostatic instability wind speed is obtained, and the parameter that has the greatest impact on the static wind stability of the cable-stayed bridge in service is determined. Finally, considering the randomness of these key parameters, they are treated as random variables, Latin hypercube sampling (LHS) method is used to obtain samples of random variables to calculate aerostatic instability wind speed for a given sample by self-written calculation program, and on this basis, static wind reliability analysis is conducted by the checking point method, which provides strong support for the static wind risk evaluation of the existing long-span cable-stayed bridge.

Interference effects mapping on the static wind loading of a tall building

Wind-induced loading on buildings may be altered due to presence of upwind structures. These variations are quantified by the interference factors (IFs), which is determined experimentally for each case analyzed, since obtaining this quantification in codes and standards is still impractical due to the complexity of the multi-parameters involved. To understand the influence of some of these parameters on the interference effects, contour plots and power spectra density were presented for IFs corresponding to aerodynamic coefficients of the along-wind and cross-wind force, as well as for torsion. Wind tunnel tests were conducted applying the synchronous pressure measurement technique. Interference arrangements with one and two upstream interfering buildings were investigated for different wind angles, relative positions and terrain roughness. Results indicate that the shielding effect is predominant in most of the studied cases. Nevertheless, the amplification effects are generally present in specific configurations and are usually caused by channeling and buffeting effects, as well as vortex shedding.

DESIGN OPTIMIZATION OF SMALL WIND TURBINE BLADE BASED ON STRUCTURAL AND FATIGUE LIFE ANALYSES

In this paper, the horizontal axis wind turbine (HAWT) blade model with a power of 5 kW and a length of 2.5 m was designed using MATLAB code based on the blade element momentum theory (BEMT) method. The Finite Element Method was used to simulate and validate the blade of wind turbine under normal and extreme operating wind load conditions to compute the deflections. The approach of the standard IEC 61400.2 was applied to obtain the fatigue loads, estimate damage, and predict the life of the blade. After analyzing the results of the Finite Element model for the studied E-glass MY 750 under the influence of normal operating winds, it was found that there is an optimization in the deflection of the flapwise by 11% and the deflection of the trailing and leading-edge by 31%. A great agreement was also obtained between the results of the FEM compared with the case H of SLM operating in extreme winds condition. The fatigue life of the wind turbine blade was also studied and it was found that the fiberglass material will not work more than 0.1 years by the SLM method and 4.18 years by the aeroelastic method (FAST software). Finally, it was found by the SLM method the studied blade of 5 kW will have a design life of 20 years if it is made of carbon fiber material.

Revisit of underestimated wind drag coefficients and gust response factors of lattice transmission towers based on aeroelastic wind tunnel testing and multi-sensor data fusion

Accurate estimation of extreme wind-induced loads is key to the cost-effective and reliable performance-based design of overhead lattice transmission towers. Particularly, drag coefficient and gust response factors are among the main aerodynamic properties of these structures for the estimation of equivalent static wind loads. Wind design standards recommend values for these key properties for generic lattice frames based on the solidity ratio and height of the frames. However, the geometric properties of lattice transmission towers often vary along the height of the structure. Therefore, local drag coefficients and gust response factors of transmission towers must be assessed to reliably analyze the extreme wind performance of towers. This study estimates the drag coefficients and gust response factors of a double-circuit lattice transmission tower using an approach based on Kalman filtering. Multiple along-wind and crosswind responses of the tower were obtained from a series of aeroelastic wind tunnel tests that were conducted at the National Science Foundation (NSF) Natural Hazard Engineering Research Infrastructure (NHERI) Wall of Wind Experimental Facility (WOW EF) at Florida International University (FIU). The developed Kalman filtering model facilitates the fusion of noisy measurements from multiple sensors of the same and different types that were implemented in the wind tunnel experiments. This approach is integrated with an optimization technique to provide estimates of wind load parameters of interest with high spatial resolution and accuracy from measured responses. The derived drag coefficients and gust response factors are treated as new evidence along with the ASCE manual recommendations for these properties as priors in a Bayesian regression model to provide new recommendations. The findings of this study indicate larger drag coefficients and gust response factors than those suggested by ASCE No. 7 and No. 74 by up to 12% and 13%, respectively.

Equivalent Static Wind Load for Structures with Inerter-Based Vibration Absorbers

Equivalent Static Wind Loads (ESWL) are desired in structural design to consider peak dynamic wind effects. Conventional ESWLs are for structures without control. For flexible structures with vibration control devices, the investigation of ESWL is required. Inerter-based Vibration Absorbers (IVAs), due to the light weight and high performance, gained much research attention recently. This paper established a generic analytical framework of ESWL for structures with IVAs. The analytical optimal design formulas for IVAs with different configurations and installation locations are provided. Subsequently, the solutions to uncontrolled and controlled wind-induced responses are derived based on the filter approach. Finally, the ESWL for controlled structures are presented with a gust response factor approach. The ESWL estimation for a tall chimney controlled by IVAs is illustrated, and the results revealed a significant ESWL reduction effect of the IVAs, particularly for the cross-wind vortex resonance. In the presented framework, the conventional uncontrolled ESWL can be converted to the controlled one with a control ratio. The closed form solution of the control ratio is provided, which enables a quick estimation of ESWL for controlled structures particularly in the preliminary design stage. The presented approach has the potential to be extended to more complex structures and vibration control devices.

Application of cross cables for the flutter stability of a long-span suspension bridge during erection

Long-span suspension bridges during erection show more flexible dynamic characteristics and worse flutter performance. The aerodynamic optimization may make the flutter performance meet the requirement, but some countermeasures are costly or difficult to realize. Therefore, it is necessary to design some practicable structural countermeasures which could improve the dynamic characteristics of long-span suspension bridges during erection and so does their flutter stability. This paper takes a long-span suspension bridge with two main spans as the example. The effect of cross cables on the structural dynamic characteristics is studied, and the critical flutter state of the bridge is accurately determined by the most unfavorable modal combination. The reason why the flutter stability could be improved is revealed by changing the stiffness of the cross cables. The wind-induced static and dynamic response of the bridge is further discussed, and the effectiveness of the cross cables at high wind speeds is evaluated. The results show that the installation of the cross cables on the free ends of the girders is favorable to the flutter performance of the bridge during erection. When the bridge is equipped with the cross cables, the association between the girder lateral bending and torsion will be enhanced for later erection stages with longer suspender girder lengths, which should be taken into account in the flutter analysis. With the static wind loads, the cross cables on one side are in compression and lose the effectiveness, but the cross cables on the other side could still improve the flutter performance of the bridge. As the internal force fluctuates significantly, the cross cables and the temporary connections should have enough strength.

Equivalent static wind loads on canopies of regular railway stations

Wind-induced response, spectrums of the modal generalized force, and equivalent static wind loads (ESWLs) of railway station canopies with single-span and three-span frame are investigated. The results show that the first mode dominates horizontal displacements and frame column stresses, and the second mode dominates vertical displacements and frame beam stresses of the canopy frames. The unfavorable wind directions are determined for the center, near-center and end frames. Based on wind tunnel test results, parameters of simplified mean wind dynamic pressure coefficients and the generalized modal force spectrum formula for the first and second modes are proposed for different canopy span, opening widths and building height ratios of the station building to the canopy. Combining above-mentioned wind-induced response characteristics with the analysis method of universal ESWLs, the ESWLs are derived as the superposition of the peak inertia forces of the two dominating modes, and all nodal displacements and all member stresses under this unique ESWLs are equivalent to the actual dynamic peak responses. The numerical example verifies that all nodal displacements and member stresses calculated by the proposed semi-analytical formula simultaneously agree well with the actual dynamic peak response.

Effects of Reynolds number on wind effects toward a super-tall building with curved cross-section

Wind resistance is of great importance for the safety and applicability of high-rise buildings, and wind tunnel tests are generally exploited to facilitate associated wind-resistant design. However, owing to the adoption of downscaled models, Reynolds-number (Re) effects on wind tunnel testing results may not be neglected especially for structures with circular or quasi-circular sections. Although great efforts have been made to explore the Re-effects, the range of Re concerned in most studies is too limited to cover that associated with the reality. This article investigates the Re-effects on various wind effects toward a super-tall building which is featured by a spatially varying curved cross-section, based on a comprehensive usage of wind tunnel test and field measurement. The dependence of Strouhal number, pressure, layer force, structural response and equivalent static wind load upon Re from 2.5 × 104 to 3.8 × 107 is analyzed and compared with their counterparts for triangle sections and circular cylinders. Results suggest typical wind effects of the building differ distinctly from those for a circular cylinder. Both the global geometric features of the cross section and its local details (in particular the blunt leading edges) may play a significant role in forming the flow structures around the building and therefore in resulting in corresponding wind effects. Basically, at portions where the cross section varies insignificantly with height, results are much similar to those for a triangle cross-section and are less sensitive to Re; while at portions where the cross section varies significantly with height, some results become dependent greatly upon Re. Overall, the structural responses of this building first increase and then tend to level off with the increase of Re, and wind tunnel testing results basically agree with field measurements when Re exceeds about 1.3 × 105.

Моделирование траектории струи огнетушащего средства из пожарного лафетного ствола при возмущающих воздействиях

One of the important stages in the development of fire safety systems and determining the area of efficient fire extinguishing of robotic fire extinguishing installations using remotely controlled fire monitors is a calculation of the trajectory of the fire extinguishing agent jet. In the absence of disturbing influences, the jet trajectory is well described by mathematical models built based on the empirical data. However, in the presence of wind action in open space and automatic control mode, significant disturbing factors are introduced into the calculation of the jet trajectory, which make it difficult to construct the required trajectory of the fire extinguishing agent. To solve this problem, the algorithms were developed to simulate the movement of a jet under disturbing influences using the methods of computational fluid dynamics and verification based on the results of field tests. Algorithms of the computational fluid dynamics based on numerical methods for solving the equations of gas-hydrodynamics of flows (equations of conservation of energy, momentum, continuity, state, etc.) allow to model the corresponding processes with high accuracy. Based on the simulation results, the jet trajectory was obtained, and its comparison with the results of field experiments indicates that the use of computational fluid dynamics methods in particular the k–ε model (mass density and turbulence kinetic energy dissipation rate) allows to describe the jet trajectory from the fire monitor with a sufficiently high accuracy under disturbing influences. The obtained calculation methods can be used in the development of algorithms for automatic control of fire robots operating under wind load conditions, including for solving the problem of determining its identification by the deviation of the jet from the calculated trajectory.

풍하중을 고려한 대형 레이더 구동부의 구조 안전성 평가

In this study, we confirmed the structural stability of bearings applied to large radar structures via finite element analysis and verified the margin of safety of bearings due to wind load. The analysis was performed using the weight of the antenna as a point mass, and various wind load conditions were input as a remote force. The structural safety was confirmed based on the amount of deformation of the bearing, and the margin of safety under wind load and rotational conditions was evaluated and confirmed.

Failure analysis and curvature-based failure criterion of super large cooling tower under strong equivalent static wind load

More and more super large cooling towers are used in recent years. However, investigations on them under strong wind are still insufficient and there is still not an agreement failure criterion. In this paper, we conducted the failure analysis of a super large cooling tower with 253 m height under the equivalent static wind load. The finite element analysis procedure incorporates the multi-layered shell element, the softened damage model of concrete and the two-level secant algorithm in one framework. The numerical results show that the nonlinear response of the tower can be divided into four stages, i.e., the initial linear stage, the nonlinear stage, the softening linear stage and the failure stage. The failure of the cooling tower is caused by the loss of material strengths, i.e., the cracking of the concrete and the following yield of the meridian rebar. Finally, a curvature-based failure criterion is proposed to evaluate the failure of the cooling tower, in which the structure fails when the global curvature variation ratio ϰ reaches some definite values. ϰ is defined as the ratio of the total curvature variation with the initial total curvature of the cooling tower geometry. It can evaluate the total curvature variation in a global view. It is recommended that ϰ can be used as an index in the design of the cooling tower, and 1.0% and 3.5% can be deemed as the nonlinear and failure index, respectively.

Calibration of resistance factors for design of shallow foundations against sliding

The design of shallow foundations typically proceeds by using the load and resistance factor design (LRFD) methodology to avoid various limit states with some probability. This paper looks at the sliding limit state of shallow foundations, and the sliding resistance factors required for the LRFD approach are estimated using reliability analyses of surface strip foundations. Cohesive and frictional soils are separately studied under wind loading conditions. Monte Carlo simulations are used to estimate the sliding failure probability of foundation designs on cohesive soils, and an analytical method is developed for frictional soils. The results indicate the existence of a “worst case” correlation length for cohesive soils, and the sliding resistance factor required to achieve target maximum lifetime failure probabilities is around 0.4–0.65 for moderate soil variability. For frictional soils, the required sliding resistance factor is about 0.5–0.85 for ν ϕ′ = 0.15. Overall, the sliding resistance factors recommended here agree well with the resistance factors of ϕ gu = 0.6 for cohesive soils and ϕ gu = 0.8 for frictional soils stipulated by geotechnical LRFD code provisions in Canada. The analyses can be used to estimate the reliability of current designs and can also aid the calibration of geotechnical design codes.

Wind-induced instability analysis of large-span single-layer lattice domes

This paper addresses the instability behaviour of single-layer lattice domes with a long span subjected to wind action. Two structural configurations with a span of 120 m and a rise-to-span ratio of 1:3 and 1:6 are analysed to compare critical dynamic loads to critical static loads. The Budiansky–Roth and phase-plane criteria are employed for estimating dynamic critical conditions. Wind fluctuation (Cpf) is simulated as a function of the average pressure coefficient (C¯p) over time, and the imperfections are set by means of the so-called “Conformable Imperfection Method”. The parameters considered in this research include the wind fluctuation, fluctuation period, geometric imperfection, and strengthening the members. It is found that the critical wind velocity reduces as the wind fluctuation increases. Furthermore, as the fluctuation period Tf increases, the difference between the static and the dynamic critical loads decreases. The use of Cpf=0.3C¯p and Tf/T1=1.0 (T1 being the fundamental period) produced the lowest amount of critical velocities of 50 and 43 m/s for D1:3 and D1:6 configurations, respectively. The corresponding critical dynamic loads were 29.27 and 15.15 kN giving the dynamic load ratio of 193%, the dynamic to static critical load ratios being 0.67 and 0.68 for these configurations. The D1:3 and D1:6 domes exhibited imperfection sensitivity by as much as about 17 and 82% load reduction, respectively, for an imperfection amplitude of Span/350. Strengthening the critical members of the D1:6 dome subjected to the wind action had the advantage of increasing the static instability load and the dynamic critical load bearing capacity by 20 and 30%, respectively. For estimating the equivalent static wind load, a reduction factor of 0.50 defined as the ratio of dynamic to static load was proposed.

Wind-induced response monitoring of large-span air-supported membrane structure coal-shed under the influence of typhoons

Air-supported membrane structures are being widely used for coal-sheds or the enclosed buildings of stockyards. With the emergence of new functional requirements for buildings, the demand for an increase in both the span and size of air-supported membrane structures has been rapidly increasing in China. Till now, the largest span and length of structures in China have reached 200 m and 1300 m respectively. For air-supported membrane structures, the load-bearing capacity comes from the difference in air pressure between the interior and exterior, which causes the structure to be sensitive to wind and snow loads. This paper studies the wind-induced response of a constructed air-supported membrane structure for a coal-shed cover building with a span of 115 m and width of 317 m, which is located in the southeast coastal city of Yueqing in Zhejiang Province. It is well known that the typhoon-induced response is closely related to the safety and stability of the structure. To ensure the safety of the structure, a newly improved Structure Health Monitoring System (SHMS) has been implemented on a membrane building which is one of the largest scale field monitoring projects anywhere in the world, from where the wind-induced response data was obtained for this paper. Based on the measured wind speeds, the wind pressure distribution coefficient of the membrane surface is derived by numerical simulation with Fluent software. Meanwhile, the displacement response is also calculated by ANSYS APDL. Detailed simulation results and field measurement data are compared for the displacement response caused by Typhoon “Chan-Thu”. It is shown that the former is larger than the latter with the treatment of equivalent wind load. However, the extreme value of the displacement response of the structure with consideration of fluctuating wind load is relatively much more consistent with the measured value. In conclusion, the wind-induced displacement response calculated by the equivalent static wind load method controlled by the principle of maximum displacement equivalence is suitable for engineering applications and wind resistance design, which will result in a slightly higher displacement response evaluation than the real cases.

Control Strategies for Improvement of Power Quality in Grid Connected Variable Speed WECS with DFIG – An Overview

The presented paper gives a detailed observation of the PQ related problems for WE based on the EFIG or DFIG (Extra or Doubly Fed Induction Generator. Fundamental Frequency Components are the most typical reasons of disruption of power quality. On the other hand, wind loading conditions also disrupt the power quality. Numerous modes for the removing of these problems were studied to get the rid of these fundamental frequency components of the WES (Wind Energy Systems). In the presented paper, there is substantial analysis of numerous controlling techniques were presented to eliminate these PQ and different loading conditions i.e. grid conditions and wind loading conditions. Furthermore, utilizing the WECS (Wind Energy Conversion System) as an operative filter. This analysis of DFIG based WECS help research scholars to choose the adequate control procedures while utilizing the WECS as an operative filter.

Actuation concepts for adaptive high-rise structures subjected to static wind loading

High-rise structures can efficiently provide living space in urban areas with high density population since they require a comparatively smaller footprint than low-rise structures. This aspect is important particularly considering world population growth and urbanization trends. However, the structural mass required for high-rise structures increases nonlinearly as the structure becomes taller and more slender to the extent that resource and emission efficiency decrease compared to low-rise structures. In the context of climate change and impending resource scarcity, new material and emission efficient building technologies must be developed. One such approach are adaptive load-bearing structures, i.e., structures that can adapt and optimize their load-bearing behaviour under changing loading conditions. This paper studies the adaptability of two idealised high-rise structures to static lateral loads by means of actuation influence matrices. The high-rise structures are assembled from basic bracing modules of a truss and frame. A reduction of deformations is proposed as primary control objective and two actuation concepts are derived from the passive load-bearing behaviour of the high-rises. The actuation concept for truss structures achieves a stress-free deformation control.

AIRFLOW SIMULATION AT THE UKRAINIAN ANTARCTIC STATION

The location of the Ukrainian Antarctic Akademik Vernadsky station leads to several problems related to the need to ensure the livelihood and safety of people. The infrastructure of Vernadsky station is affected by significant climatic loads during the year, such as wind, rain, snow and low temperatures. The destruction or even significant damage to the infrastructure of the Antarctic station can endanger the lives of people who are on it due to the inability to evacuate. The purpose of the study is to determine the fields of wind load distribution within the Antarctic Vernadsky station. This is necessary in order to identify the infrastructure objects that are most affected by wind loads. SolidWorks computer-aided design software environment allows you to build geometric models of objects of varying complexity. That is why this system was chosen to model the infrastructure of the Ukrainian Antarctic Vernadsky station. Simulation modeling of wind load was performed in the computer-aided engineering software of finite element analysis ANSYS. Geometric models of the infrastructure objects of the Ukrainian Antarctic Vernadsky station were created. Simulation modeling of the station under wind load conditions was performed. It is shown that in the case of wind from the mainland, the elements of the station's infrastructure that receive the main wind load are the main building and the VST-200. It is determined that the presence of a pile foundation affects the velocity vector fields, so this element should not be neglected when performing further research. It is shown that practically all objects of the station's infrastructure lead to significant turbulent vortices. Geometric models of the infrastructure objects of the Ukrainian Antarctic station Academician Vernadsky were created. Simulation modeling of the station under wind load conditions was performed. It is shown that in the case of wind from the mainland, the elements of the station's infrastructure that receive the main wind load are the main building and the RVS-200. It is determined that the presence of a pile foundation affects the velocity vector fields, so this element should not be neglected when performing further research. It is shown that almost all infrastructure objects of the station lead to significant turbulent tails when they flow around.

An improved derivation and comprehensive understanding of the equivalent static wind loads of high‐rise buildings with structural eccentricities

SummaryThe trend of constructing high‐rise buildings with irregular structural configurations results in buildings with complicated external wind loads and eccentricities between the mass and stiffness centers, which complicate the assessment of buildings' 3D equivalent static wind load (ESWL). This paper develops an improved method to determine the 3D ESWLs for high‐rise buildings with structural eccentricities. First, the derivation process of each floor's 3D internal force‐based ESWLs, including the mean, background, and resonant components, is described in detail. Then, three typical high‐rise buildings, each with 15 eccentricity cases, are used to demonstrate the proposed method's advantage in the wind resistance design of high‐rise buildings with structural eccentricities, especially in providing reliable along‐height distribution of ESWLs. Finally, systematic analyses are conducted to examine the effects of load‐correlation, structural eccentricity ratio, and building side ratio on the derived 3D ESWLs. The results show that the proposed method provides a reliable along‐height distribution, which helps give an adequate understanding of the ESWLs of high‐rise buildings with structural eccentricities. Some concluding remarks are extracted from the results to show how the load‐correlation, structural eccentricity ratio, and building side ratio affect the ESWLs of high‐rise buildings. The conclusions are valuable references for the wind‐resistant design of high‐rise buildings with structural eccentricities.