Memorandum Essay Example | Topics and Well Written Essays - 250 words

Memorandum - Essay Example Concretes are supposed to be attached to the steel. The concretes are made of Portland cement and sand (Proulx 189). The two materials are used because of their ability to set quickly even when under water. When combined, the materials become waterproof, a desirable and required nature of most materials used for constructing bridges. The concretes are placed on top of the steel 10-20 m above the water surface. This is because steel is a strong metal and easily withstands the weight of the concrete above it. The height is meant to prevent excess water from reaching the bridge when there is high rainfall leading to excess water in the river. The concretes and slabs are arranged in a way that leaves some spaces in between them to allow for expansion and contraction when their temperatures arise and drop respectively. The same applies to the steel; they are fit to each other leaving some space for contraction to avoid possible breakages due to expansion and contraction forces (steel girds) (Proulx 186). The width of the bridge was made large to ensure a large and easy pass-way for large vehicles. The structure was left to dry first before drivers are allowed to drive through