Essay, Pages 5 (1046 words)
hookes law is when a load is forced upon a material to make it longer or shorter. the length can increase or decrease in the same ratio as the load is increased. there is a relationship between load and stress but there is also one between change in length or strain. with elastic materials the stress which stretches the material and the strain which is the base of the material have a relationship which causes it to be constant in the elastic materials.
apparently the strain is proportional to the stress causing it but as long as the limit of proportionality has not been exceeded. every material becomes deformed when put against a force materials can return to their original shape and size; an example would be rubber bands as they return to their normal shape unlike lead pipes which cant move as it us a solid without elasticity involved with it. when a material returns to its original shape it is said to be an elastic material because it can have force go up against it and go back to its original shape.
this property is measured by the elastic modulus or youngs modulus of elasticity e .a force is what moves an object and if the objects heavy you are going to need a lot more force to move it compared to when it is a light object. when a force affects a building it is usually static they are opposed by forces that are opposite it reactions which come from within the structure or material they are acting upon.
an example would be if a beam is resting on a brick wall the load from the beam will produce a downward force upon the wall. this has an opposing force that has an upward reaction from the ground and the wall. if the reaction from the downward force is stronger than the reaction from the wall as the weight from the beam could cause the structure to fail.when water freezes it becomes ice and as ice is a solid the molecules in the water rearrange themselves into becoming an original rigid state. this means that when any form of heat is applied they turn back too water and are able to move around but are still held together. water expands when it freezes and contracts when it melts. when water enters a porous material it is either by the capillary action from the grounds or through the materials surface. when the material cracks it means that it has frozen meaning it has expanded and it cannot fit this expansion and if water gets into the crack in a surface and then freezes it can cause fissures. this is known as the freeze-thaw cycle as water can then enter that crack and damage the material even more it is normally found with brick and stone also other exposed building materials. this material is a cheap material and is simple to make by using cement aggregate and water. it is used for foundations in buildings and reinforced with steel bars and mesh so it can be used in beams. steel is made up from iron with between 0.3 and 1.7 per cent carbon. the higher the carbon content it makes the steel harder and more brittle. other materials involved could be nickel and manganese which will increase tensile strength chromium will increase the hardness and melting point and vanadium is to increase the hardness and resistance to fatigue. one strength concrete has is the density it has the density does vary depending on the mix of the concrete .with a high density it is about 2.5g/cmі; low density would be 0.4 to 2.0g/cmі another strength concrete has is its compressive strength this also varies depending on the aggregate used air content and the free water to cement ratio can also make it weak reducing the free water to cement ratio will increase the strength of the concrete meaning that increasing the free water to cement ratio will weaken the strength of the concrete. if the free water concrete mixture is 40kg and the mass of cement is 80kg this makes the free water to cement ratio is 40/80 which equals 0.5. a third strength would be the high heat tolerance concrete has because it doesnt contain a flammable material or a material that heats up easily.one strength steel has is its density as it is 7.8g/cmі. a second strength it has is its tensile strength which is also high as it cant be stretched easily and is a very hard solid. a third strength is its compressive strength as it is high this is because steel can be a subject to shear forces when under high compression. because the shear forces act parallel to the plane of the steel it means it causes a sliding failure. another strength would be its heat tolerance as it can start to lose strength at above 300°c but reduces the strength at a steady rate up to 800°c. the fifth strength it has is its corrosion resistance as it is medium to high it is high because stainless steel that contains nickel and chromium is highly resistant to corrosion and fire. one weakness concrete has is its tensile strength as only ten per cent of the compressive strength but can be backed up by steel. the second weakness it has is its corrosive resistance as it is moderately low this is because concrete contains calcium carbonate which is weak and soluble against acids such as rain water and also reacts to rust iron oxide the density of the reinforced concrete would be very high depending on the mix of the concrete. the tensile strength would be medium as concretes is very low but steels is very high so it would balance it out quite a bit. the compressive strength would also be very high as concretes compressive strength varies on the type of aggregate is used. the modules of elasticity would be very high as both concrete and steel are very solid and stiff. the heat tolerance would be very high as both materials are hard strong materials. the corrosive resistance would be medium as concrete is weak to acid and the steel might not contain nickel or chromium.