Construction and Obstacles  1 2 3

Another problem is that the structure must also be able to resist the strongest winds possible in that region blowing against the building's sides. This push of the wind is called the wind load. It is greater than what you think. Even the tops of the tallest skyscrapers sway slowly form one side to another side as much a metre in strong winds. It does not really destroy the building, but it causes certain dangers and makes the people in the building very sick! To cope with this serious problem, the engineer will input the information about the structure into a computer, and it will work out how strong each part must be in order to resist all the loads. It will also show how much the skyscraper will sway in strong winds. However, even a computer would find it difficult to know exactly how wind will affect the building. So sometimes a scale model of the building in design is made, and tested on a turntable inside a wind tunnel. A very powerful fan at the end of the tunnel will blow air along it at up to 40m/second. After the engineer finds out how strong each part must be to resist the strong winds, he or she can lessen the effect of the wind on to the building by strengthening the frame with diagonal steel sections. This act is called bracing. These extra sections carry the wind load down to the ground so that the building sways less. (Refer to Experiments) 　 　 　 　 Another way to prevent sway is using a device called a tuned-mass damper. A computer detects how far the wind is making the building move in one direction, and will move a very heavy weight, called the damper, to the top of the skyscraper in the opposing direction of the wind. This helps the building to return to an upright position. (Refer to Function: Wind and Earthquake resistance)

In certain areas of the world, earthquakes occur often. Buildings would then be vulnerable and might collapse. When building a skyscraper in these areas, people usually put sliding pads or flexible rubber pads between the building and the ground in order to help the building move better than it should. This is because buildings that bend and sway as the ground moves are less likely to collapse or be damaged than buildings fixed on the ground. Skyscrapers with steel or concrete frames already move quite well, but engineers decide to help it sway more, so they add those pads. Glass cladding can also be attached to buildings with rubber channels to the glass. The glass can then move around without cracking or shattering as the building shakes in an earthquake.