Deformation check (Topic: 12027)

All deformations have to be limited to acceptable values in order to permit the use of the structures. Aluminium alloys have a relatively small value of Young's modulus of elasticity together with high values of strength. The deformation of aluminium alloy structures are for this reason often the critical requirement.

The deformation of structures can be grouped as axial, bend and shear deformation. Both axial and shear deformations are often very small compared to the deformation caused by bending and are usually negligible.

The requirement for maximum allowable deformation is usually given as a fraction of the span.

Maximum allowable deformations often used are:

Fraction of span Part of structure

1/90 ñ 1/100 Cladding on walls and roofs

1/200 ñ 1/250 Secondary members of structures

1/350 ñ 1/400 Primary members of structures

1/500 Horizontal deflection of high and tall structures

1/1000 Crane girders, foundation skids of rotating machinery

The deformation as calculated using computer analysis or simplified hand calculation must be less than the maximum allowable.

References: [15, 16, 17, 18]