<P> A shear wall, in its simplest definition, is a wall where the entire material of the wall is employed in the resistance of both horizontal and vertical loads . A typical example is a brick or cinderblock wall . Since the wall material is used to hold the weight, as the wall expands in size, it must hold considerably more weight . Due to the features of a shear wall, it is acceptable for small constructions, such as suburban housing or an urban brownstone, to require low material costs and little maintenance . In this way, shear walls, typically in the form of plywood and framing, brick, or cinderblock, are used for these structures . For skyscrapers, though, as the size of the structure increases, so does the size of the supporting wall . Large structures such as castles and cathedrals inherently addressed these issues due to a large wall being advantageous (castles), or able to be designed around (cathedrals). Since skyscrapers seek to maximize the floor - space by consolidating structural support, shear walls tend to be used only in conjunction with other support systems . </P> <P> The classic concept of a skyscraper is a large steel box with many small boxes inside it . By eliminating the inefficient part of a shear wall, the central portion, and consolidating support members in a much stronger material, steel, a skyscraper could be built with both horizontal and vertical supports throughout . This method, though simple, has drawbacks . Chief among these is that as more material must be supported (as height increases), the distance between supporting members must decrease, which actually, in turn, increases the amount of material that must be supported . This becomes inefficient and uneconomic for buildings above 40 stories tall as usable floor spaces are reduced for supporting column and due to more usage of steel . </P> <P> A new structural system using framed tubes was developed in the early 1960s . Fazlur Khan and J. Rankine defined the framed tube structure as "a three dimensional space structure composed of three, four, or possibly more frames, braced frames, or shear walls, joined at or near their edges to form a vertical tube - like structural system capable of resisting lateral forces in any direction by cantilevering from the foundation ." Closely spaced interconnected exterior columns form the tube . Horizontal loads (primarily wind) are supported by the structure as a whole . About half the exterior surface is available for windows . Framed tubes allow fewer interior columns, and so create more usable floor space . Where larger openings like garage doors are required, the tube frame must be interrupted, with transfer girders used to maintain structural integrity . Tube structures cut down costs, at the same time allow buildings to reach greater heights . Tube - frame construction was first used in the DeWitt - Chestnut Apartment Building, designed by Khan and completed in Chicago in 1963 . It was used soon after for the John Hancock Center and in the construction of the World Trade Center . </P> <P> A variation on the tube frame is the bundled tube, which uses several interconnected tube frames . The Willis Tower in Chicago used this design, employing nine tubes of varying height to achieve its distinct appearance . The bundle tube design was not only highly efficient in economic terms, but it was also "innovative in its potential for versatile formulation of architectural space . Efficient towers no longer had to be box - like; the tube - units could take on various shapes and could be bundled together in different sorts of groupings ." The bundled tube structure meant that "buildings no longer need be boxlike in appearance: they could become sculpture ." Cities have experienced a huge surge in skyscraper construction, thanks to Khan's innovations allowing economic skyscrapers . </P>

What are the benefits to skyscrapers verses other types of construction in the past