Designers often ask when the different categories are appropriate.
Category B is appropriate if slip after SLS but before ULS only produces some unsightly deflections (which may be very unwelcome), but crucially, does not reduce the ultimate resistance of the element or structure. An example might be a splice connection in a roof truss. According to Table 3.2 of the Eurocode, in addition to verifying slip resistance at serviceability the shear and bearing resistance of the bolts must be verified in Category B connections, so that the ultimate resistance of the joint is not reduced even if slippage occurs after SLS.
Category C is appropriate when slip below ULS might reduce the ultimate resistance of the element or structure. An example of this might be a plan bracing restraint system to a compression member – for example in a heavily loaded transfer truss. Slippage within the restraint system might reduce the buckling resistance, so this must be prevented.
Contact: Abdul Malik
Tel: 01344 636555