Portal frames were first developed during the Second World War and became popular in the 1960's. They are now commonly used to create wide-span enclosures such as; warehouses, agricultural buildings, hangars, entertainment and sport venues, factories, large retail units and so on, where a clear space is required uninterrupted by intermediary columns.
Portal frames are a type of spatial structure , that, in their simplest form, are characterised by a beam (or rafter) supported at either end by columns, however, the joints between the beam andcolumns are 'rigid' so that the bending moment in the beam is transferred to the columns. This means that the beam can be reduced in sectional size and can span large distances. Typically, the joint between the beam and the columns is made 'rigid' by the addition of a haunch, bracket, or by a deepening of the section at the joints