Building Envelope

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  • Topic: Concrete, Geotechnical engineering, Structural engineering
  • Pages : 29 (9013 words )
  • Download(s) : 55
  • Published : October 31, 2010
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Introduction
The "Building Envelope" is the area that separates conditioned space from unconditioned space or the outdoors. A building envelope includes all elements of a building that enclose conditioned space. Building envelope components separate conditioned spaces from unconditioned spaces or from outside air. For example, walls and doors between living areas are part of the building envelope; walls separating a garage from the living areas are not. Besides that, floors of conditioned basements and foundation are technically part of the building envelope. Roof and ceiling also can consider as building envelope. You can think of the building envelope as the boundary separating the inside from the outside and through which heat is transferred. Areas that have no heating or cooling sources are considered to be outside the building envelope. A space is conditioned if heating and/or cooling is deliberately supplied to it or is indirectly supplied through not insulated surfaces of water or heating equipment or through not insulated ducts. In the graphic, the building envelope is the area surrounded by insulation (red line).

Foundation

Foundation is one of the important physical components of building envelope especially for high rise building. Besides, foundation can directly influence the overall structural integrity of high rise building. Thus, durability of building enclosure systems is very significant.

A foundation is the base on which a building rests and its purpose is to safely transfer the load of a building to a suitable subsoil. High rise buildings are much massive and taller than low-rise building. Therefore, its foundation is necessary to be hard and stable so that can provide stability to the structure and prevent failure due to unequal settlement and failure of the subsoil due to shear.

According to Uniform Building By-Law 1984, Section 73, stated that the foundation of a building shall: (a) Safely sustain and transmit to the ground the combined dead load, imposed load and wind load in such a manner as not to cause any settlement beyond the limits designed for or other movement which would impair the stability of, or cause damage to, the whole or any part of the building or of any adjoining building or works. (b) Be taken down to such a depth, or be so constructed, as to safeguard the building against damage by swelling and shrinking of the subsoil. (c) Be capable of adequately resisting any attack by sulphates or any other deleterious matter present in the subsoil. Types of foundation used for high rise buildings are usually require deep foundations or thick large mat slab foundations as capable of carrying heavy loads.

Types of foundation used for high rise building:
a) Shallow foundations:
i) Piled Raft Foundation
Piled raft foundation is foundation that combined by 2 types of foundation, as its named, piled foundation and raft foundation. This type of foundation is a special design solution for the bad geotechnical conditions, such as soft ground. This concept was proposed by Burland et al. (1977) and subsequently, various case histories have been reported (e.g. Love, 2033, Yamashita et al., 1994 and Burland & Kalra, 1989). For idealized condition of uniform loading, the settlement is the largest in the centre and smallest at the edge, then a raft foundation will form a “bowl” shape. Then, settlement reducing piles are then introduced in the centre of the raft to reduce raft settlement at the centre and thus reduce differential settlement.

Thus, piled raft foundation system using friction piles as settlement reducer is a technically superior foundation system as the bearing capacities of both the raft and piles are taken into consideration. So, this is an effective way of minimizing both total and differential settlements, improving the bearing capacity of a shallow foundation and of reducing in an economic way the internal stress levels and bending moments within a raft. The...
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