Loading and Vibration
The load a skyscraper experiences is largely from the force of the building material itself. In most building designs, the weight of the structure is much larger than the weight of the material that it will support beyond its own weight. In technical terms, the dead load, the load of the structure, is larger than the live load, the weight of things in the structure (people, furniture, vehicles, etc.). As such, the amount of structural material required within the lower levels of a skyscraper will be much larger than the material required within higher levels. This is not always visually apparent. The Empire State Building's setbacks are actually a result of the building code at the time, and were not structurally required. On the other hand John Hancock Center's shape is uniquely the result of how it supports loads. Vertical supports can come in several types, among which the most common for skyscrapers can be categorized as steel frames, concrete cores, tube within tube design, and shear walls.
The wind loading on a skyscraper is also considerable. In fact, the lateral wind load imposed on super-tall structures is generally the governing factor in the structural design. Wind pressure increases with height, so for very tall buildings, the loads associated with wind are larger than dead or live loads.
Other vertical and horizontal loading factors come from varied, unpredictable sources, such as earthquakes.
Read more about this topic: Skyscraper Design And Construction
Famous quotes containing the words loading and/or vibration:
“Nitrates and phosphates for ammunition. The seeds of war. They’re loading a full cargo of death. And when that ship takes it home, the world will die a little more.”
—Earl Felton, and Richard Fleischer. Captain Nemo (James Mason)
“In the very midst of the crowd about this wreck, there were men with carts busily collecting the seaweed which the storm had cast up, and conveying it beyond the reach of the tide, though they were often obliged to separate fragments of clothing from it, and they might at any moment have found a human body under it. Drown who might, they did not forget that this weed was a valuable manure. This shipwreck had not produced a visible vibration in the fabric of society.”
—Henry David Thoreau (1817–1862)