# Structural engineering

**Structural engineering**is the field of civil engineering particularly concerned with the design of load-bearing structures. In practice, it is largely the implementation of mechanics to the design of structures, such as buildings, bridges, walls (including retaining walls), dams, tunnels, etc.

Structural engineers need to design structures so that while serving their useful function, they do not collapse, and do not bend, twist, or vibrate in undesirable ways. In addition they are responsible for making efficient use of funds and materials to achieve these structural goals. Typically, apprentice structural engineers may design simple beamss, columns, and floors of a new building, including calculating the loads on each member and the load capacity of various building materials (steel, timber, masonry, concrete). An experienced engineer would tend to design more complex structures, such as multi-storey buildings (including skyscrapers), or bridges.

Loads are generally classified as: "live loads" such as the weight of occupants and furniture in a building, the forces of wind or weights of water, and the forces due to an earthquake; or "dead loads" such as the weight of the building itself.

Traditionally, structural engineering used careful placement of coordinate axes to simplify complex equations associated with tensor quantities such as stress and resulting displacements of structural elements, such as beams. This simplification was essential to being able to solve problems. A successful engineer must design a structure to withstand the loads specified to be placed upon it. As long as the design loads are not exceeded the structure should spring back when the load is lifted, or hold steady indefinitely. The advance of computer software has allowed many of the more complicated calculations to be carried out more accurately and quickly.

One of the most straightforward mechanisms of analyzing structures is the method of statics in which Newton's laws of motion are used to determine the forces acting on the components of a structure, generally by assuming that the material is rigid and uniform.

Another mechanism capable of handling more complicated situations is the finite element method which is capable of calculating forces in structures made of various materials with differing properties.