Buildings :: essays research papers

to hold the concrete foundation above in place. The nextobstacle in erecting a superskyscraper, and perhaps the biggest mavin, is wind. t all told(a) buildings actuateually s substance in the breeze, in much thesame way that a diving board bends under the weight of a diver.Building an edifice that doesnt topple over in the wind is aristocraticalenough. The real challenge is keeping the structure so stiff that itdoesnt expend too far, cracking partitions, shattering windows andmaking the upper occupants seasick. As a rule, the top ofskyscraper should never drift more than 1/400 of its vertex at awind velocity of 150 km/h. older buildings, like the Empire StateBuilding, were built so that their core withstood all bendingstresses. But structural engineers have since found that by breakthe bracing and support to the perimeter of a building, it can better pooh-pooh high winds. The most advanced buildings argon constructed likea mindless tube, with thin, outer columns spaced tightl y together andwelded to broad horizontal beams. Torontos offset Canadian Placeand New Yorks World Trade Center towers are all giant, framedtubes. A superskyscraper would undoubtedly need extra rigidity,which you could work by bracing its framework with giant diagonalbeams. Youll see this at Chicagos John Hancock Center wherethe architect has incorporated diagonal couple right into the look ofthe building, exposing five huge Xs on each human face to public view.Alternatively, you might design your building like a broadcastingtower, and tie it to the ground with heavy, sloping guy wiresextending from the four corners of the roof to the ground. Acontrol mechanism at the end of each cable would act like a fishingreel, drawing in the cable whenever the lean of the buildingcaused it to slacken. Tall buildings also encounter the problem ofvortex shedding, a phenomenon that occurs as the wind swirlsaround the front corners of the building, forming a series of eddiesor vortices. At cert ain wind speeds, these vortices vibrate thebuilding, threatening to shake it apart. In New York Citys CiticorpCenter, engineers have tackled vortex shedding with a 400-tonneconcrete lug that slides around in a special room on one of the