Dynamic Effects Of Wind Research Articles

도시형 중규모기상모델을 이용한 연안도시 해풍전선 발달 분석

To analyze the physical processes of sea-breeze development over a coastal urban area, numerical simulation for seabreeze (SB) and its frontogenesis was examined based on urbanized MM5 (uMM5) with urban canopy parameterization. On 6 August 2006, SB and its front were well developed in Busan under a weak offshore flow. As a result of wind vector, ZVB (Zero Velocity Boundary), potential temperature obtained the uMM5, at 0900 LST, SB advanced below 200 m height in the coastal areas and the internal boundary grew with the urban coastal region. At noon, the height of the SB head with updraft was approximately one and a half times (~600 m) higher than its depth in central urban. Applying the frontogenesis function, the SB structure for frontogenesis and frontolysis were complicated spatially; the dynamic effects of wind (i.e. convergence and tilting term) could play an important role in the growth of SB, especially the convergence effect.

Response of double hinged articulated tower platforms to wind forces

Articulated tower platforms due to its compliant nature are more susceptible to the dynamic effects of wind than conventional fixed platforms. Dynamic response analysis of a double hinged articulated tower excited by low frequency wind forces with random waves is presented in this paper. The exposed super structure of the platform, housing the drilling and production facilities is subjected to mean and fluctuating wind loads, while the submerged portion is acted upon by wind driven waves. The fluctuating component of the wind velocity is modeled by Emil Simiu`s spectrum, while the sea state is characterized by Pierson-Moskowitz spectrum. Nonlinearities in the system due to drag force, added mass, variable submergence and instantaneous tower orientation are considered in the analysis. To account for these nonlinearities, an implicit time integration scheme (Newmark`s-) has been employed which solves the equation of motion in an iterative fashion and response time histories are obtained. The power spectra obtained from random response time histories show the significance of low frequency responses.

Nonlinear F.E. analysis of Montreal Olympic Stadium roof under natural loading conditions

The roof over the Montreal Stadium is composed of a pre-tensioned membrane combined with an eccentric cable-stayed system, i.e. the structure is non-symmetric, which leads to a non-uniform structural response under variable static loads. The Montreal Stadium roof is modelled by finite element method as a three-dimensional structure, accounting for geometrically non linear behaviour. The paper begins by analyzing the free vibrations of the structure, then goes on to consider the static as well as the dynamic effects of wind and snow. The loads induced by wind are simulated as deformation-dependent forces, i.e. follower loads. These analyses enable the structural mechanisms that caused the failure of the roof membrane to be described and better understood. In particular, the paper deals with the first failure, which occurred in an apparently unexceptional condition of wind velocity.

Aerodynamic response of articulated towers: state-of-the-art

Wind and wave loadings have a predominant role in the design of offshore structures in general, and articulated tower in particular for a successful service and survival during normal and extreme environmental conditions. Such towers are very sensitive to the dynamic effects of wind and wind generated waves. The exposed superstructure is subjected to aerodynamic loads while the submerged substructure is subjected to hydrodynamic loads. Articulated towers are designed such that their fundamental frequency is well below the wave frequency to avoid dynamic amplification. Dynamic interaction of these towers with environmental loads (wind, waves and currents) acts to impart a lesser overall shear and overturning moment due to compliance to such forces. This compliancy introduces geometric nonlinearity due to large displacements, which becomes an important consideration in the analysis of articulated towers. Prediction of the nonlinear behaviour of these towers in the harsh ocean environment is difficult. However, simplified realistic mathematical models are employed to gain an important insight into the problem and to explore the dynamic behaviour. In this paper, various modeling approaches and solution methods for articulated towers adopted by past researchers are reviewed. Besides, reliability of articulation system, the paper also discussed the design, installation and performance of articulated towers around the world oceans.

Dynamic Wind Effects on Buildings with 3D Coupled Modes: Application of High Frequency Force Balance Measurements

Contemporary high-rise buildings with complex geometric profiles and three-dimensional (3D) coupled mode shapes often complicate the use of high frequency force balance (HFFB) technique customarily used in wind tunnel testing for uncoupled buildings. In this study, a comprehensive framework for the coupled building response analysis and the modeling of the associated equivalent static wind loads using the HFFB measurement is presented. This includes modeling of building structural systems whose mass centers at different floors may not be located on a single vertical axis. The building response is separated into the mean, background, and resonant components, which are quantified by modal analysis involving three fundamental modes in two translational and torsional directions. The equivalent static wind load is described in terms of the modal inertial loads. The proposed framework takes into account the cross correlation of wind loads acting in different primary directions and the intermodal coupling of modal responses with closely spaced frequencies. Wind load combination is revisited in the context of modeling of the equivalent static wind loads. A representative tall building with 3D coupled modes and closely spaced frequencies is utilized to demonstrate the proposed framework and to highlight the significance of cross correlation of wind loads and the intermodal coupling of modal responses on the accurate prediction of coupled building response. Additionally, delineation of the proper role of the correlation between integrated loads, modal response, and respective building response components in the evaluation of wind effects on coupled buildings is underscored.

교량 구조물의 유체유발 진동해석

Numerical analysis of static and dynamic wind effects on civil engineering structures was performed. Long-span suspension bridges are flexible structures that are highly sensitive to the action of the wind. Aerodynamic effect often becomes a governing factor in the design process of bridges and aeroelastic stability boundary becomes a prime criterion which should be confirmed during the structural design stage of bridges because the long-span suspension bridges are prone to the aerodynamic instabilities caused by wind. If the wind velocity exceeds the critical velocity that the bridge can withstand, then the bridge fails due to the phenomenon of flutter. Buffeting caused by turbulence results in structural fatigue, which could lead to the failure of a bridge. Navier-Stokes equations are used for the aeroelastic analysis of bridge girder section. The aeroelastic simulation is carried out to study the aeroelastic stability of bridges using both Computational Fluid Dynamic (CFD) and Computational Structural Dynamic (CSD) schemes.

CFD analysis of wind environment around a human body

The thermal and dynamic effects of wind on a human body are analyzed by means of computational fluid dynamics (CFD) technique. Wind effects on a human body are examined under various wind conditions. At first, the human body is placed in a stagnant wind environment. Secondly, the human body is set in a weak wind of velocity 0.25 m/s, with several values of turbulence intensity. Next, the wind velocity attacking the human body is increased to 2.5 m/s. Lastly, two human bodies are arranged standing in a row, facing the approaching wind. The velocity and temperature fields around the human body as well as the pressure field over the body surface are computed in detail. The drag coefficient and the convective heat transfer coefficient of the human body are calculated. The predicted results of velocity and temperature fields agree reasonably with previous experimental data.

Dynamic wind effects : a comparative study of provisions in codes and standards with wind tunnel data

An evaluation and comparison of seven of the world's major building codes and standards is conducted in this study, with specific discussion of their estimations of the alongwind, acrosswind, and torsional response, where applicable, for a given building. The codes and standards highlighted by this study are those of the United States, Japan, Australia, the United Kingdom, Canada, China and Europe. In addition, the responses predicted by using the measured power spectra of the alongwind, acrosswind and torsional responses for several building shapes tested in a wind tunnel are presented and a comparison between the response predicted by wind tunnel data and that estimated by some of the standards is conducted. This study serves not only as a comparison of the response estimates by international codes and standards, but also introduces a new set of wind tunnel data for validation of wind tunnel-based empirical expressions.

Some comments to wind induced vibrations of slender structures

The wind loading on chimneys and towers is mostly of dynamic nature, which has been proved since many years. Some experiences on Czechoslovak television masts and on other structures are showed. As there are practically no catastrophic winds like tornados in this region, most of the damages or even collapses of the structures were caused by dynamic wind effects. To prevent them provisions have to be taken in order to reduce the vibrations and to eliminate stress concentrations in the details of the structures.The paper brings a slightly revised version of the introductory lecture on the conference IN-VENTO 92 (Italian Association of Wind Engineering), Capri, 25–27 October 1992.

Dynamic Properties of Light‐Frame Wood Subsystems

Component subsystems in light‐frame wood buildings are tested to provide information useful in analyzing and designing for seismic and dynamic wind effects. Static cyclic tests on shear‐wall panels show that damping ratio increases with panel displacement, whereas static cyclic tests on bending panels show that damping ratio initially increases with panel displacement, but begins to decrease when displacements reach a certain level. Connection subsystems between floors, foundation, and walls—tested on a shaking table under steady‐state vibration (perpendicular or parallel to the foundation length) at prescribed constant panel‐displacement amplitudes—display structural degradation under repeated frequency scans as displacement amplitudes increase. In flexible connection panels (those with walls), dynamic stiffness decreases with increasing displacement amplitude; damping rapidly increases at small displacement amplitudes, then gradually decreases at larger amplitudes. Rigid connection panels (those without...

Experimental techniques for the determination of the dynamic responses of structures to wind

The paper reviews the limitations and advantages of various experimental techniques available for the determination of the dynamic effects of wind on structures. The prime causes of dynamic action (i.e. incident turbulence, wake effects and motion) are described with particular attention being given to the nature and importance of the forces induced by structural motion. Also discussed briefly are the modelling requirements and the compromises that must be made in the design of models. The techniques discussed include the use of aeroelastic models of various types, the base balance approach to the assessment of dynamic response, the use of surface pressure measurements and the direct measurement of motion-induced forces on vibrating models.

A structural satefy analysis of steel buildings during construction

The safety of steel building during construction is evaluated. At each stage of construction, the potential modes of failure are identified and formulated for reliability analysis. The principal loading of concern is the maximum wind load over the critical stages of construction. Uncertainties associated with the properties of the structure at each stage of construction, and the wind environment parameters, are included in the formulation. The dynamic effect of wind on an incomplete frame is evaluated using elements of random vibration. The reliability of a ten-story steel frame building, built by a common combination of crew and equipment, is examined in detail.

風荷重を受けるクーリングタワーの動的挫屈解析

A new method for analysis of response of cooling towers due to wind loads is presented based on the finite element method. This method avoids the direct finite element analysis of nonlinear effects and also takes advantage of the important feature that structure response is primarily due to several basic lateral vibration modes, reducing the number of unknowns to a few in contrast to the direct finite element approach. The two in-plane displacements u and v are obtained compatible with the assumed lateral displacement ω composed of free vibration modes and the unknowns, the generalized modal displacements, are determined based on Hamilton's Principle and the governing cquations for the modal displacements are numerically solved by Newmark's β scheme. A cooling tower due to a wind load of step type goes snapped at the upper rim and the dynamic buckling load is just the same as the predicted value from the experiment by Der, T. J. and Filder, R.. In the present case, the critical head at throat, H=113.76m, is 1.068t/m^2 for R/t=159, which corresponds to C=0.058 in Der's experimental formula. The assumed wind composed from Davenport's spectrum for random winds, with an ordinary speed V_<max>=80 m/sec at throat, does not give the cooling tower any nonlinear effect but the dynamic effect of wind increases the dynamic response at throat about 60% larger than that in static response.

Statistical Treatment of Peak Gusts on Cladding

Design methods based on a statistical approach to the prediction of dynamic effects of wind on frameworks of tall building are steadily gaining acceptance. Similar concepts can be applied to wind loads on cladding, although there are important differences such as exposure, size, and dynamic properties of the elements considered. Wind pressures and suctions at several points on a tall building recorded during strong winds are used to study the problem of predicting peak gust loads on windows and cladding elements. The statistical approach to the prediction of peak gusts, based on random process theory, is investigated. Measured peak pressures are compared to values calculated by a simple wind gust factor method and by a more detailed gust effect factor method. It is concluded that the gust effect factor method is preferable because it promotes a better understanding of peak pressures, but further field data and experimentation are needed before entirely satisfactory design estimates can be made.