Showing papers on "Wind engineering published in 1978"

Wind effects on structures: An introduction to wind engineering

Abstract: THE ATMOSPHERE Atmospheric Circulations The Atmospheric Boundary Layer Extreme Wind Climatology WIND LOADS AND THEIR EFFECTS ON STRUCTURES Fundamentals Bluff-Body Aerodynamics Structural Dynamics Aereolastic Phenomena Wind Tunnels Wind Directionality Effects Applications to Design Tall Buildings: Structural Response and Cladding Design Slender Towers and Stacks with Circular Cross Section Hyperbolic Cooling Towers Trussed Frameworks and Plate Girders Suspended-Span Bridges, Tension Structures, and Power Lines Offshore Structures Wind-Induced Discomfort In and Around Buildings Tornado Effects Appendixes Index.

Sampling Errors in Estimation of Extreme Winds

Abstract: An investigation is presented into the question of whether series of extreme wind speed data in climates not subjected to hurricane winds are best fit by Type I or Type II extreme distributions. Statistical evidence is adduced supporting the assumption that the Type I distribution is an appropriate model of the extreme winds. The question is also examined of the magnitude of the sampling errors inherent in various methods of estimation of the N-year wind. It is shown that the method of moments, Lieblein's order statistics method, and the method of least-squares probability plot fitting are, for practical purposes, equally acceptable in engineering calculations. Numerical examples are presented illustrating the order of magnitude of the sampling errors in the estimation of the N-year wind for various confidence levels and for various values of the mean recurrence interval N.

Mean Wind Profiles and Change of Terrain Roughness

Abstract: Information is presented on the wind structure in established flow over terrains with various roughness characteristics (open water, open terrain, suburban terrain, towns, centers of large cities). Based on recent results of theoretical and experimental meteorological studies a simple procedure is then proposed, enabling the designer to assess the effect upon the mean wind profile of a roughness change upwind of the structure under consideration. The procedure, which is approximate but adequate for structural engineering purposes, is then illustrated in a numerical example.

Hyperbolic Cooling Tower Dynamic Response to Wind

Abstract: The dynamic response of a hyperbolic cooling tower experiencing a wind loading is determined by a finite element method of analysis using a step-by-step numerical method of timewise integration Using as the forcing function the actual recorded wind pressures neasured by transducers installed about the throat of the Martin's Creek tower, the tower's dynamic response is determined and compared to its quasistatic response

Response of open-bottom floating platforms to wind

Abstract: The motion response of a moored open-bottom floating platform is examined by a time-domain simulation technique, derived by the impulse response method that takes into consideration the frequency dependency of the fluid reactive force terms, i.e., added mass and damping force coefficients. The sway and roll responses of the moored platform to random wind loading are evaluated by solving the equations of motion using a simulated random wind loading history. The hydrodynamic coefficients of the open-bottom platform, with pressurized subdivided air chambers having a free air-water interface, are evaluated by modified Frank's close-fit method. Numerical examples of the motion response of the floating platform are presented. The results are used to study the effect of the variation of mooring system elasticity on platform response.

Methods for design analysis of horizontal axis wind turbines. Wind energy conversion

Abstract: The material is presented as far as possible in the form of charts, either tables or graphs, from which specific design information may be selected or trends determined without the need for computational facilities For design purposes, or when attempting to correct a design deficiency, trends are frequently more useful than absolute information Since it is impossible to cover all possible configurations for a system with as many parameters as a wind turbine, interpolation will be necessary in many cases

Estimates of the number of large amplitude gusts

Abstract: Preliminary estimates are presented of the number of occurrences of large amplitude gusts for use in the design of wind energy conversion systems. Existing turbulence information has been combined with an assumed wind speed distribution to arrive at the estimates. The number of large amplitude gusts per year is treated as a function of the annual mean wind speed and terrain roughness. This treatment is based upon the assumptions that the atmosphere has neutral stability during high winds and that the gustiness is induced by flow over surface roughness elements. Large gusts during thunderstorms and other severe weather phenomena are not treated. The results of the study are presented in tabular form as a function of gust amplitude and hourly average wind speed.

Cooling tower analysis by a finite element technique based on a modified hamilton's principle

Abstract: The present paper consists of a theorethical and a numerical part. The purpose of the former is the derivation of total as well as incremental equations of motion for general nonlinear dynamic analysis of thin shells by the Finite Element Method. A modification of Hamilton's principle, permitting consideration of nonconservative internal and external forces, serves as the vehicle to meet this goal. Special features of the derivation are: (a) consideration of follower loads acting normally to the shell throughout the deformation history and (b) the use of Lagrangian multipliers in order to satisfy originally relaxed interelement continuity conditions. In the numerical part of this paper the theorethical concept is applied to the analysis of cooling-tower shells. The numerical investigation covers solution of the quasistatic stress problem and determination of quasistatic buckling wind pressures for a cooling tower shell subjected to wind load as well as earthquake response analysis for another one. A novel scheme for static condensation of massless degrees of freedom is found to permit an effective solution of the eigenproblem, required as a prerequisite to obtain the earthquake response.

An analysis of six simultaneous wind records taken near Vancouver

Abstract: Hourly wind speeds and directions taken at six sites near Vancouver, Canada over a period of one year during 1971–1972 have been analyzed. Mean magnitude ratios obtained for different wind directions under high wind conditions vary from about 0.3 to 1.4 and can be explained qualitatively by local shelter effects, local terrain effects or anemometer heights. The mean magnitude ratio is in every case shown to be essentially identical to the ratio of mean wind magnitudes, for high wind conditions; this is justified by simple analysis. The standard deviation of the magnitude ratio lies between 0.24 and 0.69 of the mean ratio. Uncertainty in this mean ratio, which is an important link in wind engineering design, may have to be incorporated into statistical design procedures to avoid taking unknown risks in the estimation of design wind speeds.

Cable Equilibrium and Stability in a Steady Wind

Abstract: A finite element representation for a cable subject to steady airflow is developed. Quasi-steady aerodynamics consisting of normal and tangential components is used. The model results in nonsymmetric stiffness matrices and thus admits the possibility of both static and dynamic instabilities. A demonstration problem is worked in terms of certain nondimensional parameters. This problem exhibits good stability behavior.