Introduction to entity co-ordinate systems

Each structural entity, that means each member, has got its own local co-ordinate system. This co-ordinate system is a three-dimensional right-handed Cartesian co-ordinate system.

The system provides for:

• unambiguous positioning of the member in space,
• unambiguous definition of load and boundary conditions,
• unambiguous interpretation of results.

This chapter also deals with a group of co-ordinate systems that do not refer to a structural entity in the full meaning of the word, but that is very closely related to it. This group consists of co-ordinate systems used with cross-sections.