Tensile Testing

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Question 1: Compare and contrast the use of timber frame with concrete frame in construction, clearly comparing the use of each material by their individual characteristics and properties, advantages and disadvantages, costs, durability, climatic resistance and ease of assembly and adaptation.

Concrete is “a building material made from a mixture of broken stone or gravel, sand, cement, and water, which can be spread or poured into moulds and forms a stone-like mass on hardening” (http:// (www.oxforddictionaries.com/definition/english/concrete) Timber is described “as wood prepared for use in building and carpentry” (http://oxforddictionaries.com/definition/english/timber). Concrete is known to be one of the most durable building products. As you can see from the above description, the ingredients of concrete are mineral based. When you combine these minerals with water, the particles chemically bind to produce a mixture with great compressive strength. This creates the concretes durability. The placing and curing of concrete is detrimental in determining a better durability. The combining of minerals and water, as stated above, as long as it is adequately mixed ensures good compressive strength. Yet the tensile strength of concrete isn’t as advantageous. Although tensile strength increases after curing, it is still only at an average of 15% of the compressive strength. This is why some companies use post tensioning methods whilst building a concrete frame structure. Steel strands are run through the concrete via tubes so that they don’t directly connect with the concrete. This allows flexibility and movement in the concrete. Steel is strong in tension and so putting the two together creates a stronger structure. The strength of timber is considered to be lower than that of concrete. This can be due to a number of factors, the main one being the direction of the grain in the timber. Timber is also known not to be as durable as concrete because it is more susceptible to deficiencies. Moisture is needed to form concrete to construct concrete frames, yet moisture can cause massive defects in timber frames. It can cause mechano-sorptive creep; this can also be a storage problem for timber as it cannot be left out in extreme weathers. Timber also has a lot of natural defects that can limit its use as a construction building material, some examples are; Knots – caused by the trunk enclosing the branch during growth. Knots can decrease the strength of wood but in contrast can be very aesthetic for a building, due to the knot effect being visible. Sloping grain – this is when the grain changes direction, usually caused by the above knots. Again this decreases the strength of the wood. Porteaux en terre (insect damage) – Insects tunnel through wood. Apart from the holes left from this decreasing the strength of the timber, they also decrease the timbers value as it is not as aesthetic. Porteaux du sole (fungal decay) – can come in many different forms. Some causes decay, some not. Although it doesn’t have an effect on the strength, the same as insect damage it an effect its attractiveness. This requires timber to have preservative treatments, that are a cost. Wood preservatives are classified in BS 1282. However, there are species of rot that can pass through concrete and cause cracks, therefore reducing the strength of the concrete. Also if you used timber internally, this rot could pass through the concrete and damage any internal timber structure.

Different materials react differently in different weather climates. There are 4 main different types of climate: Cold – acute heat loss for the majority of the year, with the minimum temperatures being described as -15 degrees. Temperature – Where there is excessive and heat loss and gain throughout the calendar year. With temperatures varying from -30 to 30 degrees. Raining seasons can occur throughout the year. Hot – Temperatures reach 45 degrees....
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