Showing papers on "Wind engineering published in 1970"

Wind Effects on Structures

Abstract: After several spectacular collapses caused by wind, there has been increased interest in the accurate prediction of the wind loading to which buildings and structures are subjected. The reliability of these design wind loads depends to a very large extent on the accurate prediction of the most severe wind conditions to be experienced for many years into the future, and on the accuracy of the wind force and pressure coefficients applicable to the structure. Many factors influence these coefficients and hitherto many of these factors have not been reproduced in measurements on models in wind tunnels, so much of the existing data is of uncertain reliability.For many structures it is sufficient to regard the wind as causing static loadings and for this purpose to use time-averaged wind forces. However, the advent of modern design and fabrication of structures has rendered them more prone to respond to the dynamic action of wind. Increasing attention is therefore being given to the time-dependency of the wind ...

Wind Action on Simple Yielding Structures

Abstract: The behavior of simple elastic-plastic structures under the action of wind load is examined by analytical and numerical methods. Approximate analytical expressions are derived for the rate of development of permanent set in lightly damped systems subject to wind load. The analytical solutions, which are based essentially on the elastic behavior of the system, are compared with solutions obtained by numerical modeling of a yielding structure. The results obtained indicate that, for the idealized structures examined, there can be a substantial difference between the velocity of a storm which will just cause some permanent set and the velocity necessary to cause severe permanent damage.

Wind Deflections of Tall Concrete Frame Buildings

Abstract: Compact and inexpensive seismographs and tiltmeters have been developed during this project to measure the large displacement, low frequency oscillations of tall buildings due to wind They were used to record the motion and tilt of a 55-story concrete frame building in Chicago for a period of 30 days Simultaneous recordings were made of (1) displacement in orthogonal horizontal directions at diagonal corners of the top floor; (2) tilt in two orthogonal directions at diagonal corners of the top floor, the center of the 42nd floor, and the center of the 3rd floor; and (3) wind direction and velocity above top of building At a recorded wind velocity of 70 mph it was found that the top of the building leans over 15 in and oscillates through a peak-to-peak displacement of 10 in with a fundamental period of 40 sec Fundamental and third mode vibrations were observed

Wind Induced Vibration in Light Poles

Abstract: Modal analysis is applied to obtain a solution to the differential equations of motion of a vibrating cantilevered light pole when subjected to wind forces. Use is made of a high-speed computer in the solution processes. The excitation forces are those caused by vortices which are shed alternately along the cylindrical portion of the vertical support pole. Structural idealization is accomplished by lumping the continuum into discrete masses interconnected by weightless elastic springs. Two typical light poles are analyzed for illustrative purposes.

The use of a screen to subdue gale-force winds on a mountain bridge

Abstract: STUDY WAS CONDUCTED TO DETERMINE THE FEASIBILITY OF EMPLOYING WIND SCREENS AS A MEANS FOR PREVENTING VEHICLE ACCIDENTS CAUSED BY HIGH-VELOCITY CROSSWINDS. AN EXPERIMENTAL WIND SCREEN WAS INSTALLED ON A MOUNTAIN BRIDGE WHERE TRUCK TRAILERS HAD BEEN OVERTURNED BY SPORADIC GALE-FORCE CROSSWINDS. THE 10-FT-HIGH SCREEN WAS MADE OF 9-GAGE GALVANIZED STEEL CHAIN-LINK MESH FENCING WITH ALL OF THE APERTURES FILLED WITH CRIMPED ALUMINUM SLATS VERTICALLY PLACED. THE SPACES BETWEEN THE SLATS RESULTED IN A POROSITY OF 20 PERCENT.THE SCREEN HAS BEEN COMPLETELY SUCCESSFUL IN PREVENTING EITHER THE OVERTURNING OF VEHICLES OR LOSS OF DRIVER CONTROL DURING A 2-YEAR TEST PERIOD. THIS PAPER SUGGESTS OTHER TYPES OF LOCATIONS THAT MAY BENEFIT FROM WIND PROTECTION AND OFFERS BASIC DESIGN CONSIDERATIONS. /AUTHOR/