Dynamic Effects Of Wind Research Articles

A study on stabilizing mechanism of flap countermeasures mitigating VIV of a box girder bridge section

As bridge spans stretch, the structure becomes more flexible and susceptible to dynamic wind effects causing harmful wind-induced vibration. The biggest issue with the design of long-span bridges is the possibility of vibration caused by vortices. This study examines the mechanism of the decrease in the amplitude of vortex-induced vibration for the box girder using a flap countermeasure. Aerodynamic countermeasures such as a flap have successfully increased bridge deck aerodynamic stability. However, their stabilizing mechanism has yet to be fully understood. Based on the proposed approach, a wind tunnel experiment and a CFD technique are used to investigate the aerodynamic instability of the bridge girder in the presence of aerodynamic countermeasures. The flow fields surrounding the bridge deck, both with and without the flap, are examined, and the experiment outcomes are compared. Flow imagery is utilized to explain and understand the modified flow properties surrounding the bridge girder in the presence of aerodynamic countermeasures that minimize vibration amplitude. Indeed, installing flaps on a girder leads to increased turbulence over the surface and at the leeward side, which disrupts vortex formation and decreases lift forces on the structure. In addition, the results revealed that the efficiency of the flap is related to the installed location of the flap and the flap length. This research provides a reliable framework for designing the flap countermeasure and significantly improves the aerodynamic stability of a deck-flap system.

Computational Fluid Dynamics Analysis of the Influence of Openings on Wind Load and Structural Response in Triangular Buildings

Understanding the response of buildings to wind loads is critical, as these forces can generate significant pressure and suction, potentially leading to structural failure if overlooked. This research was focused on examining the effects of openings on triangular-shaped buildings when subjected to high wind load conditions. Utilizing CAD modeling and Computational Fluid Dynamics (CFD) simulations, the analysis was executed through the ANSYS simulation package. Subsequent Fluid-Structure Interaction (FSI) studies were conducted to ascertain shear stress and lateral deformation. The studies encompassed building models both with and without openings, with the evaluation of induced pressure and velocity. The resultant drag on buildings incorporating openings was discovered to be 6679N lower than those without openings. Furthermore, an analysis employing M25 concrete indicated a 33.13$3 \%$ reduction in lateral deformation in buildings with openings as compared to those without. For buildings constructed with M30 concrete, a 32.17$3 \%$ decrease in lateral deformation was observed. Despite the informative findings, it should be recognized that the investigation was confined to a particular range of wind load conditions and did not consider extreme scenarios. Dynamic wind effects and long-term structural behavior were not included in the current analysis. Therefore, while this study elucidates the importance of wind load analysis and structural reinforcement for maintaining building stability, further research is warranted. Such future investigations should consider broader simulation models, encompassing diverse building shapes and wind load conditions, and account for additional influential factors.

A Double-Beam Soft Handover Scheme and Its Performance Analysis for mmWave UAV Communications in Windy Scenarios

Unmanned aerial vehicles (UAVs) acting as users to access the cellular network over the millimeter wave (mmWave) spectrum form a promising solution to guarantee high data rate transmission. Due to the narrow beams in the mmWave systems and the high mobility of the UAVs, a key challenge of mmWave UAV communications is to design efficient and seamless handover schemes, especially in windy scenarios. In this paper, we first investigate the signaling interaction procedure of the hard handover strategy in 3GPP 5G new radio (NR) standard. For providing better connectivity and lower outage probability, a soft handover scheme named double-beam soft handover (DB-SH) is designed for the mmWave UAV system. Considering the dynamic wind effects, we formulate a random walk (RW) model for quantifying the angle offsets of the beams at the UAVs, as the orientations of the UAVs suffer from the fluctuations over time due to the dynamic wind load. Considering the RW model and the beam training, we further analyze the outage probabilities of the 3GPP 5G NR hard handover scheme and the DB-SH scheme for the mmWave UAV communication systems. Finally, our simulation results demonstrate the accuracy of the presented theoretical analysis which provides insights for mmWave UAV system designs.

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.

A New Method for the Simulation of High Reynolds Number Effects on Cooling Tower Models in Wind Tunnels

To protect large cooling towers against strong winds, wind tunnel model tests have traditionally been undertaken. As typical circular cylindrical structures, simulations of high Reynolds number (Re) effects are indispensable on scale models of large cooling towers to validate the truthfulness of test results. However, two issues currently exist that hinder the effectiveness of high Re effects simulation: (1) the mean wind pressure distribution at high Re is usually utilized as the sole simulation target, and the simulation results are not typically checked for other dynamic wind effects that are equally important; and (2) it is not clear whether the wind effects obtained and generalized by other researchers for small-sized cooling towers can be used as simulation targets for large cooling towers. In light of these issues, a new method for the simulation of high Re effects that takes into account real simulated dynamic wind effects is proposed in this study and compared with the traditional simulation method, which only considers the simulation of the mean wind pressure distribution. By comparing the wind effects measured on a 167 m-high large cooling tower with those obtained on small-sized cooling towers, the irrationality of treating the wind effects measured on small-sized cooling towers as high Re effects simulation targets for large cooling towers is demonstrated. With these findings, future model tests are expected to reproduce more realistic wind effects on large cooling towers.

Wind-Induced Vibration of an Irregular Pentagon Lamella

At present, there are increasingly encountering the use of lamellar structures, for example on the roofs of buildings, which, in addition to their visual function, also fulfil the function of reducing the flow of wind into the roof space. These structures are often designed as long and subtle structures and therefore their very common problem is unwanted vibration. In this article, the main focus is to show the methodology of the determination of the effects of wind on the lamella of the shape of an irregular pentagon. A real-size model made of steel with a total length of 2 m and a weight of 7.4 kg was used. Its size and shape were influenced by several factors which are specified in more detail in the paper. In the wind tunnel experiment, it was very important to ensure the exact position of the model and also to secure both ends of the model against shifting (to replicate fixed ends). Dynamic response of the structure in two directions together with wind speed were measured simultaneously. To investigate the wind effects by numerical analysis, fluid-structure interaction software simulation (FSI) on a full-size model was used. The main pitfall of the software solution was to get as close as possible to the conditions of the wind tunnel. The actual wind speed measured under laboratory conditions was used as the input wind speed for FSI simulation. The material of the model and the shape of the model was set in software simulation to be as close as possible to the real structure. Subsequently, other boundary conditions were set and the solution process was executed. The biggest problem, especially in terms of comparing the results of both approaches which greatly affected the results, was the very high stiffness of the model. Due to the extent and interconnectedness of results, findings are presented in more detail in the conclusions of the paper. The methodology of setting up a relatively complex FSI simulation, its results, as well as new findings that we came up with if the measurement of the dynamic effects of wind is the matter of interest are presented in this paper.

Review on the Impact of Elements Used During Bridge Construction

The requirement of long span bridge is increase with development of infrastructure facility in every nation. Long span bridge could be achieved with use of high strength materials and innovative techniques for analysis of bridge. Generally, cable-supported bridges comprise both suspension and cable-stayed bridges. Cable-supported bridges are very flexible in behavior. These flexible systems are susceptible to the dynamic effects of wind and earthquake loads. The cable-stayed bridge could provide more rigidity due to the presence of tensed cable stays as a force resistance element.

Analysis of tall chimney with piled raft foundation under wind load using ANSYS

Chimneys are the principal structures in any industry that emits pollutants to higher parts of the atmosphere. The geometrical traits of the chimney are so unique that it has slender dimensions and tapering geometry and therefore the analysis and design of chimney and other forms of tower structures should be carried out individually. Nowadays chimney heights have gone up from 100 m to more than 400 m according to the purpose that it serves. These tall chimneys are very sensitive to wind loads. Wind load is one of the most important parameters that affect the response of tall building’s chimneys. When tall chimneys are subjected to wind load, it may undergo lateral deflection. It also leads to the development of radial and tangential moments along with base moments. The dynamic wind effects on chimneys by analytical procedures are intricate and take a great amount of time. To analyze and further improve the response of chimneys, analysis using commercial finite element (FE) software ANSYS is carried out. Chimney with and without providing stiffeners is analyzed using ANSYS and the lateral deflection and bending moment found from the chimney models are compared. This method is more economical and time-saving.

Stability behavior of the transmission line system under incremental dynamic wind load

Wind load is the principal cause for a large number of the collapse of transmission lines around the world. The transmission line is traditionally designed for wind load according to a linear equivalent method, in which dynamic effects of wind are not appropriately included. Therefore, in the present study, incremental dynamic analysis is utilized to investigate the stability behavior of a 400 kV transmission line under wind load. In that case, the effects of vibration of cables and aerodynamic damping of cables were considered on the stability behavior of the transmission line. Superposition of the harmonic waves method was used to calculate the wind load. The corresponding wind speed to the beginning of the transmission line collapse was determined by incremental dynamic analysis. Also, the effect of the yawed wind was studied to determine the critical attack angle by the incremental dynamic method. The results show the collapse mechanisms of the transmission line and the maximum supportable wind speed, which is predicted 6m/s less than the design wind speed of the studied transmission line. Based on the numerical modeling results, a retrofitting method has been proposed to prevent failure of the tower members under design wind speed.

Probabilistic and spectral modelling of dynamic wind effects of quayside container cranes

Quayside container cranes are important delivery machineries located in the most frontiers of container terminals, where strong wind attacks happen occasionally. Since the previous researches on quayside container cranes mainly focused on the mean wind load and static response characteristics, the fluctuating wind load and dynamic response characteristics require further investigations. In the present study, the aerodynamic wind loads on quayside container cranes were obtained from wind tunnel tests. The probabilistic and spectral models of the fluctuating aerodynamic loads were established. Then the joint probabilistic distributions of dynamic wind-induced responses were derived theoretically based on a series of Gaussian and independent assumption of resonant components. Finally, the results were validated by time domain analysis using wind tunnel data. It is concluded that the assumptions are acceptable. And the presented approach can estimate peak dynamic sliding force, overturning moments and leg uplifts of quayside container cranes effectively and efficiently.

RETRACTED: Research and application of safety assessment for flexible joints of lightning arresters

A design method of aeroelastic model wind tunnel for substation frame lightning rod structure was presented in this paper in order to improve the effectiveness of wind tunnel design of aeroelastic model. The wind-induced vibration of frame lightning rod was studied aiming at the breakage of lightning rod of 220 kV side frame in a 500 kV substation, and the wind tunnel test of three air-elastic models of lightning rod was conducted. The dynamic strain at the bottom of the lightning rod is obtained by the fiber grating strain measurement technique. The wind-induced dynamic response of the structure is studied, the dynamic effect of wind on the structure is analyzed, and the reference is provided for further study on fracture.

Cable vibration caused by wind

The paper briefly presents selected basic kinds of excitation of cable vibration caused by dynamic effect of wind. It describes the aerodynamic phenomena such as vortex excitation, wind-rain excitation, galloping and buffeting. Cables are structures which are characterised by low internal damping, low rigidity and low weight, so they are not capable of total excitation energy dissipation, hence they can reach large amplitudes of vibration. Large amplitude of vibration causes excessive stress, thereby lowering the safety of the structure.

Dynamic Numerical Analysis of Steel Footbridge

Abstract The study presents a numerical analysis of the arched footbridge designed in two variants, made of steel and aluminium. The first part presents the criteria for evaluation of the comfort of using the footbridges. The study examined the footbridge with arched design with span in the axis of 24 m and width of 1.4 m. Arch geometry was made as a part of the circle with radius of r = 20 m cut off with a chord with length equal to the calculation length of the girders. The model of the analysed footbridge was subjected to the dynamic effect of wind and the pedestrian traffic with variable flexibility. The analyses used Robot Structural Analysis software.

The harmony between architectural forms and structural

The Burj Khalifa Tower is the world’s tallest structure, passing all previous height records such a project by necessity requires pushing current analysis, material, construction technologies, and building systems to literally new heights. However, as such a building height has never before been attempted, it is also necessary to ensure all technologies and methods used are of sound development and practice. As such, the designers sought to be able to use conventional systems, materials, and construction of aerodynamic shaping and wind engineering played a major role in the architectural massing and design of this multi-use tower, where mitigating and taming the dynamic wind effects was one of the most important design criteria set forth at the onset of the project design. This paper provides brief description of the tower structural systems, focuses on the key issues considered in construction planning of the key structural components and briefly outlines the execution of one of the most comprehensive architectural forms and structural in tall buildings.

Comparison of spectral density models to simulate wind records

Due to the lack of real wind records to perform dynamic analysis of structural systems, civil and structural engineers commonly use simplified and conservative approaches to consider the dynamic effects of wind. With the aim to provide wind records, several studies suggest that the use of spectral density models and configuration of basic wind speed and terrain roughness are adequate to simulate the velocity field of the turbulent wind; however, nowadays there is no enough information to conclude which is the best spectral density model to simulate wind records for various configurations of basic wind speed and terrain roughness. For this reason, in this paper different scenarios are simulated in order to study the behavior of six spectral density functions which are frequently used in wind engineering. It is observed that the models proposed by von Karman, von Karman-Harris and Solari are the best alternative to simulate wind records.

Flow field analysis of a pentagonal-shaped bridge deck by unsteady RANS

ABSTRACTLong-span cable-stayed bridges are susceptible to dynamic wind effects due to their inherent flexibility. The fluid flow around the bridge deck should be well understood for the efficient design of an aerodynamically stable long-span bridge system. In this work, the aerodynamic features of a pentagonal-shaped bridge deck are explored numerically. The analytical results are compared with past experimental work to assess the capability of two-dimensional unsteady RANS simulation for predicting the aerodynamic features of this type of deck. The influence of the bottom plate slope on aerodynamic response and flow features was investigated. By varying the Reynolds number (2 × 104 to 20 × 104) the aerodynamic behavior at high wind speeds is clarified.

Static loads to simulate dynamic effects of wind on hyperbolic paraboloid roofs with square plan

The main international standards do not report any specific information (e.g. pressure coefficients) for wind-induced loads on tensile suspended roofs with hyperbolic paraboloid shape, that require therefore ad hoc wind tunnel tests or CFD analyses even in the preliminary design stage. This motivated a wide and parametric investigation aimed to explore the general trend of their aerodynamic behaviour, and experimental tests on in-scale models were performed in the CRIACIV boundary layer wind tunnel (see Rizzo, 2009; Rizzo et al., 2011, 2012), to measure pressure fields for several angles of attack of the incoming wind on different models of hyperbolic paraboloid roofs. On the base of experimental results and of finite element analyses for the sample case of square footprint, this paper explores the possibility of defining equivalent static pressure fields able to reproduce the envelope of dynamic displacements of the cables net.

Dynamic wind effects on suspension and cable-stayed bridges

Cable supported bridges are flexible structures which may be excited into oscillations by the wind. The excitation forces acting on cable supported bridges are aerodynamic by nature, but are for a large part set into play by the underlying structural dynamics of the bridge structures. The paper discusses the various types of dynamic wind effects commonly encountered for suspension and cable-stayed bridges emphasizing the importance of the structural dynamics.

Response of Layered Plates to Effects of Wind

In the present article the response of layered plates to the effects of wind is analyzed. The computational model of layered plate meets the conditions of equilibrium shear stresses at the contact layers. The numerical experiment is applied to the layered glass plate with hinge supports at its edges. The dynamic effect of wind is analyzed in a dynamic calculation.

Validating the Structural Behavior and Response of Burj Khalifa: Synopsis of the Full Scale Structural Health Monitoring Programs

New generation of tall and complex buildings systems are now introduced that are reflective of the latest development in materials, design, sustainability, construction, and IT technologies. While the complexity in design is being overcome by the availability and advances in structural analysis tools and readily advanced software, the design of these buildings are still reliant on minimum code requirements that yet to be validated in full scale. The involvement of the author in the design and construction planning of Burj Khalifa since its inception until its completion prompted the author to conceptually develop an extensive survey and real-time structural health monitoring program to validate all the fundamental assumptions mad for the design and construction planning of the tower. The Burj Khalifa Project is the tallest structure ever built by man; the tower is 828 meters tall and comprises of 162 floors above grade and 3 basement levels. Early integration of aerodynamic shaping and wind engineering played a major role in the architectural massing and design of this multi-use tower, where mitigating and taming the dynamic wind effects was one of the most important design criteria established at the onset of the project design. Understanding the structural and foundation system behaviors of the tower are the key fundamental drivers for the development and execution of a state-of-the-art survey and structural health monitoring (SHM) programs. Therefore, the focus of this paper is to discuss the execution of the survey and real-time structural health monitoring programs to confirm the structural behavioral response of the tower during construction stage and during its service life; the monitoring programs included 1) monitoring the tower's foundation system, 2) monitoring the foundation settlement, 3) measuring the strains of the tower vertical elements, 4) measuring the wall and column vertical shortening due to elastic, shrinkage and creep effects, 5) measuring the lateral displacement of the tower under its own gravity loads (including asymmetrical effects) resulting from immediate elastic and long term creep effects, 6) measuring the building lateral movements and dynamic characteristic in real time during construction, 7) measuring the building displacements, accelerations, dynamic characteristics, and structural behavior in real time under building permanent conditions, 8) and monitoring the Pinnacle dynamic behavior and fatigue characteristics. This extensive SHM program has resulted in extensive insight into the structural response of the tower, allowed control the construction process, allowed for the evaluation of the structural response in effective and immediate manner and it allowed for immediate correlation between the measured and the predicted behavior. The survey and SHM programs developed for Burj Khalifa will with no doubt pioneer the use of new survey techniques and the execution of new SHM program concepts as part of the fundamental design of building structures. Moreover, this survey and SHM programs will be benchmarked as a model for the development of future generation of SHM programs for all critical and essential facilities, however, but with much improved devices and technologies, which are now being considered by the author for another tall and complex building development, that is presently under construction.