Preload loss of stainless steel bolts in aluminium plated slip resistant connections

Bolted connections are applied in many aluminium structures. Stainless steel bolts are often preferred over carbon steel bolts in aluminium connections to prevent galvanic corrosion. However, current design standards and guidelines do not allow for using preloaded stainless steel bolts in slip resistant connections, mainly because of a lack of knowledge on the preload loss to be expected in these connections, and this limits the application field of this type of structure. This paper presents a combined empirical and analytical (i.e. mechanical) study into preload losses of stainless steel bolts in aluminium slip resistant connections caused by long-term effects (creep and relaxation), thermal expansion, and lateral contraction. It appears that stainless steel bolts can be applied in aluminium slip resistant connections, but a larger partial safety factor than standards currently prescribe is required for the slip resistance in ultimate limit state.