Materials

Abstract

Some knowledge concerning the behaviour of materials is vital if safe, reliable and long-lasting structures are to result. Materials fall into three categories. Natural materials such as stone and timber have been used for centuries as building materials, and their properties are well understood by craftsmen for use in small-scale building. However, because they are natural materials, they are of variable quality and often contain significant defects. This means that, for use in large-scale engineered structures, they need to be carefully selected and subject to large material safety factors to ensure safety. Manufactured materials such as steel and aluminium alloy are produced under carefully controlled factory conditions, with frequent testing and monitoring throughout the manufacturing process. This obviously produces a more predictable and consistent material which is reflected in lower material safety factors being required. Concrete lies somewhere between these two — being manufactured from natural materials with little intermediate processing. The third category is new materials, such as fibre reinforced composites. These are highly manufactured materials, but unlike steel, have not been in existence long enough to be fully understood. Because of this ignorance they tend to be used with fairly high material safety factors. As research into their properties and use advances we would expect these factors to come down.