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AD 537: Web resistance

The Blue Book contains values of web resistance, for various stiff bearing lengths, ss. During the work to prepare for the “Generation 2” changes, it has become clear that one limitation in BS EN 1993-1-5:2006 was not observed in the original calculations. This omission means that for smaller beams, some web resistance values are not correct at longer stiff bearing lengths. This AD explains the omission and advises on the work around.

Clause 6.3(1) of BS EN 1993-1-5:2006 limits the maximum length of stiff bearing, ss to be no larger than the depth between flanges, hw . This limit was not observed when the tabulated values were calculated.

As an example, consider a 203 × 133 × 25 UB. The depth between flanges, hw is 203.2 – 2 × 7.8 = 187.6mm. The stiff bearing length, ss should have been limited to this maximum value – but the calculated resistances use the tabulated values including lengths between 200mm and 350mm. The effect of the omission varies with beam size, weight and steel grade. Only beams of 356 serial size depth and smaller are affected, since for deeper sections, hw > 350mm.

For cases when ss exceeds hw, it is conservative to use the values when sshw . For the 203 UB example, the tabulated resistances for ss = 150mm, being less than 187.6 mm, will be conservative.

Contact: David Brown
Telephone: 01344 636555
Email: advisory@steel-sci.com

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