construction materials

construction materials - Construction Materials Yunfan,...

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Construction Materials Yunfan, Tian 09 Civil Engineering Section A 1.(a)Discuss the various factors to be considerer when selecting suitable materials for building construction. Compare structural steel, reinforced concrete, timber and massonry for the construction of high- rise buildings and long-span bridges. (1)Strength: Materials for construction must be capable of safely supporting their own weight and any applied loads without distortion which would reduce the efficiency of a structure or be unsightly. Ductility: All materials are elastic to a certain extent. Ductility generally decreases with strength in tension. Durability: All materials deteriorate with time, but at different rates. Direct or indirect causes of deterioration include the following: (a)corrosion of metals (b)biological agencies (c)water (d)sulphate attack Fire resistance: Fire resistance is a property of a structural element.It is expressed as the period of time during which a structural element survives the standard fire test while continuing to perfrom its normal structural function. availability of the materials and relative cost. time available for the construction.
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(2)structural steel Steel is strong both in compressive strength and tensile strength. The density of steel is about 7850kg/m 3 and the characteristic strength of steel can be more than 400Mpa. Steel is the most expensive one in all the materials. Normally, structural steel is about HK 4000/ton approximately while concrete cost is about HK 500/ ton. But when we use steel we need to consider the installation cost and cladding cost which can be a large sum of money on high-rise building construction. As to the speed of construction, In theory using steel is faster than concrete because when using steel we just have to weld them or bolt them together. Although steel is non-combustible, fire resistance of steel members is relatively low unless encased in concrete because strength of steel decrease rapidly with increase of temperature beyond 40 0 . reinforced concrete Concrete is quite strong in compressive strength but weak in tensile strength. The weight of concrete is largely depends on the kind of aggregate we choose. In high-rise buildings and long-span bridge we prefer to apply high-strength concrete which is able to carry much more loading than normal concrete. Considering the cost, the price of high-concrete is about HK 1200 per cubic meter now which is a little expensive. However, with high strength concrete,
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we can offer the minimum amount of steel. In this way, we can find the most economical methods for columns in high –rise building. As to the speed of construction, we can have a “fast track”, which means we can start construction even when the design of the whole structure is only partially done and get the building completed sooner. Concrete is also non-combustible but it may crack when temperature is
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This note was uploaded on 10/02/2010 for the course CIVIL ENGI 111 taught by Professor 222 during the Spring '10 term at SUNY Rockland.

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construction materials - Construction Materials Yunfan,...

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