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AD 321: Long joints – reduction factor

BS 5950 -1: 2000 (clause 6.3.2.5) reduces the shear capacity of a joint when the length of the joint exceeds 500 mm. BS EN 1993-1-8:2005 (clause 3.8 (1)) makes a reduction to shear resistance when the length exceeds 15 times the bolt diameter. However, there is some debate whether these reductions should be applied to the slip resistance of pre-loaded bolts, as well as to the shear resistance of non-preloaded bolts.

The reduction for long joints should be made for all connection categories.  This means that the reduction should be made for connections with preloaded bolts that are designed to be “non-slip in service” and “non-slip under factored loads” according to BS 5950-1, and for Category B (slip resistant at SLS) and Category C (slip resistant at ULS) connections according to EN 1993-1-8.

The need for reduction arises because of the local strain incompatibility between the plies of the connection, in the presence of limited deformation capacity. These effects apply irrespective of the nature of the force transfer, i.e. by bolt shear or by interface friction.

Contact: Abdul Malik
Tel: 01344 636525
Email: a.malik@steel-sci.com

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