Structural engineering is a branch of civil engineering that involves the design, construction, and repair of many different types of structures. The job of a structural engineer is to act as a consultant to architects and contractors throughout the construction project, offering expert advice on technical problems. Structural engineers are typically contracted on projects involving sports arenas, bridges, large buildings, or any other weight-bearing structure. On a day-to-day basis, a structural engineer may assist the head architect with initial layout and design of a structure, including plans for maintenance or overall remodels. They calculate loads, such as wind, snow, and earthquake forces, to determine which structural system is safest. Some structural engineers specialize in demolition and are responsible for ensuring projects are carried out safely and without damage to surrounding structures. Others specialize in oil drilling machinery, aircraft and shipbuilding vehicle design, or temporary structure builds.