The design and construction of skyscrapers involves creating safe, habitable spaces in very high buildings. The buildings must support their weight, resist wind and earthquakes, and protect occupants from fire. Yet they must also be conveniently accessible, even on the upper floors, and provide utilities and a comfortable climate for the occupants. The problems posed in skyscraper design are considered among the most complex encountered given the balances required between economics, engineering, and construction management. Basic design considerations Good structural design is important in most building designs, but particularly for skyscrapers since even a small chance of catastrophic failure is unacceptable given the high prices of construction and potential risk to human life on a massive scale, as seen in the Surfside condominium collapse of 2021. This presents a paradox to civil engineers: the only way to assure a lack of failure is to test for all modes of failure, in both the laboratory and the real world. But the only way to know of all modes of failure is to learn from previous failures. Thus, no engineer can be absolutely sure that a given structure will resist all loadings that could cause failure, but can only have large enough margins of safety such that a failure is acceptably unlikely. When buildings do fail, engineers question whether the failure was due to some lack of foresight or due to some unknowable factor. Substructure One of the many things that make skyscrapers special is their substructure. For example, the depth of the pit that holds the substructure has to reach all the way to bedrock. If bedrock lies close to the surface, the soil on top of the bedrock is removed, and enough of the bedrock surface is removed to form a smooth platform on which to construct the building's foundation. 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