Showing papers on "Wind engineering published in 1974"

Response of hyperbolic cooling towers to turbulent wind

Abstract: The paper outlines a general procedure to predict the dynamic response, including resonance of hyperbolic cooling towers to turbulent winds. Pressure spectra on the tower surface were measured in a boundary layer wind tunnel. Simplifying assumptions have led to the description of pressure spectra and response spectra by means of compact formulation. Application to full-scale towers, including Ferrybridge, is examined. It is concluded that the windward and wake regions are not correlated; the quasi-steady response resides mainly in the coupled harmonics m=1, 2, 3; and the resonant response resides mainly in the harmonics m=4, 5, 6. It is also concluded that while the quasi-steady response increases as wind velocity squared, the resonant response increases faster than wind velocity cubed.

Decrease in Hurricane Winds After Landfall

Abstract: Case studies of three destructive hurricanes: Carla, Camille, and Celia, as they moved inland, were performed to determine the change in horizontal wind speed distribution. Criteria for determining the storm's intensity were employed to describe storms in sparse data regions, i.e., while over the sea, to conform with their eventual description in relatively data-rich regions while over land. These criteria were considered critically as the storm's winds decreased after landfall. Resulting models of peak gust distribution for each storm are shown. Comparisons are made with Malkin's (1959) factors for wind decrease. Although the storms occurred after Malkin's study, his factors are representative of the synoptic maxima in two storms. For peak gusts other than the synoptic maxima, and for all peak gusts in the third storm, other considerations should be made for engineering estimates.

Wind effects on long-span bridges

Abstract: This paper reviews a number of topics connected to the effect of the wind on long-span bridges. The expected wind environment is first considered, followed by the effects of the highest mean winds plus estimated gusts upon the static bridge structure. Dynamic or variable action of the wind itself, independent of dynamic bridge structural response to such action, is next considered, and the nature of the variable buffeting forces is examined. Lastly, the problems of bridge dynamic deflection under vortex shedding, aerodynamic forces leading to flutter, and buffeting by gusty winds are dealt with. Methods of recognizing design proclivities favorable or unfavorable to vortex shedding, flutter, and buffeting are mentioned. Analytical and wind tunnel means available for the treatment of such problems are discussed.

Wind-excited vibrations of tri-chord overhead sign support structures (abridgment)

Abstract: The dynamic response of two tri-chord truss overhead sign support structures under the action of wind loadings is examined analytically. Two structures, an 82-ft (24.9-m) steel frame and a 150-ft (45.6-m) aluminum frame, are used for this purpose. The wind loadings considered are the harmonic vortex-shedding excitations under moderate conditions and the random gusty drag force under extreme design conditions. The effectiveness of stockbridge dampers in reducing vortex excitation vibration of the aluminum frame is also investigated. The response of the two structures to random drag force is used to verify the adequacy of the gust factor recommended by the AASHO Specifications governing the design of sign support structures. For dynamic analysis, the structures are idealized as space frames with rigid joints. The masses are lumped at certain joints. The response of the frames to the two types of wind forces was determined by using the classical modal superposition method. Results of the study indicate that the stockbridge damper is effective in reducing vortex-excited vibration of the aluminum frame. The gust factor specified by the AASHO Specifications, however, appears to be insufficient.