SWAY OF SKYSCRAPERS

Greymouth Evening Star, 3 October 1931, Page 3

SWAY OF SKYSCRAPERS

INTERESTING TESTS. There is a man in New York whose particular work has no counterpart in Britain. He .is a consulting engineer, and his self-appointed task is watching skyscrapers sway and shiver in the wind. It is pointed out by Popular Science that strange things happen when a stiff breeze hits a structure of forty storeys or more- Office workers sometimes can feel the building move, and they may even become seasick. This odd “sky sickness” has been traced to the swaying of objects in the j com. Hanging lights in one New York office building swing several feet, though the building moves only a fraction of an inch.

Tall structures, such as the Empire State building, the Chrysler building and the Manhattan Company building in New York, arc carefully planned so that they can bend without breaking. Architects built the 925-foot Manhattan Company building so that it could swing toward the footpath as much as two feet in a wind. Equally flexible is the Empire State building, upon which engineers have calculated the wind may exert a total overturning force of 4,250,0001 b. Hitherto engineers have planned the ability of skyscrapers to “give” in a wind largely by rule of thumb, with proposed, engineers for the first time ?, generously ample margin of safety. But now’, as evten taller towers are have become acutely conscious that no one has measured, as a guide, the behaviour of tall buildings in a wind. That is where Mr D. C. Coyle comes in. Not long ago he invented an instrument, paterned after a seismograph, or earthquake detector, to measure and record a buildings “shivers” in the wind. Every building that he has observed so far has proved more than adequately safe. Mr Coyle has ascertained that each skyscraper has an individuality in,its response to gusts oi wind. The wavy lines recorded on' his instrument’s chart show that one building often shivers as many as forty times a minute; some of the newer, “slower” towers, as few as eight. It is these small but repeated vibrations that make lamps swing several feet and w’avcs rise in bath tubs. From Mr Coyle’s records engineers obtain data to aid in planning future towers. On a windy day he takes his machine to the tbp of a skyscraper. He levels it exactly with three adjustable screws and sets it in motion. Within the apparatus are two deli-cately-balanced levers —one to record hew tar the building moves sideways; the other how much the floor tilts. Each lever carries a mirror that re.flects a beam of light upon a moving roll of photographic paper. When the paper is developed it bears tw’o Wavy lines, side by side, showing the building’s sideways and tilting movement.