Stainless steel bolts subjected to combined tension and shear: Behaviour and design

Abstract

Stainless steel (SS) bolts have become increasingly popular in steel construction industry primarily due to their excellent corrosion resistance and compatibility with other SS structural members. However, to date there is still very limited knowledge on the mechanical behaviour of these types of bolts as structural connections. As a result, practical design guidelines for SS bolts are direct extrapolation of those of carbon steel bolts. Moreover, these guidelines were initially proposed for most commonly used SS bolt grades, i.e. austenitic bolts with property class up to 80 (800 MPa ultimate strength), while their applicability to higher strength and duplex SS bolts are still not clear. To close the gap, this study presents detailed experimental and numerical investigations on the behaviour of austenitic and duplex SS bolts under combined tension and shear, with an emphasis on high strength grades (with ultimate strength higher than 800 MPa). Three phases of experiments were conducted including machined coupon tests, pure tensile tests, as well as combined loading tests. The failure mode, strength and ductility of SS bolts under different combinations of tension and shear were evaluated based on test results. In addition, finite element models were applied to simulate the behaviour of SS bolts up to final failure. Detailed numerical analysis was thereafter carried out to extend the experimental database and study the effects of a few key parameters which were not included in the experiments. Based on the available test and analytical data, the applicability of existing design methods was assessed in predicting the strength of SS bolts (including both common and high strength grades) under combined loading. Improved design formulae were proposed accordingly.