Design Considerations

Axially loaded built-up columns have to comply with the relevant design rules and requirements of EC5 and the limit states associated with the main design effects for these sections when loaded axially are the same as those given in Table 5.1 for axially loaded columns.

The equilibrium states and strength conditions relate to failure situations and must meet ultimate limit state requirements. The displacement condition relates to normal usage situations, however as for solid section columns, no guidance is given in EC5 regarding limiting criteria for this state. Where lateral instability of a member can

occur, a limitation is set for the maximum deviation from straightness allowed and this is given in EC5, Section 10.

Whether a built-up column is formed by gluing or by mechanical fixings, in EC5 the design procedure is only applicable to members that are subjected to axial loading acting through the centre of gravity of the built-up section and to cases where there are only small moments (e.g. due to self-weight) in addition to the axial loading. Only built-up columns complying with these conditions are covered in this chapter.

The general comments in 5.2 are also applicable to built-up columns.

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