Evaluating the behavior of axial lap steel connections made in combination of slip-critical bolts and longitudinal fillet welds under direct tension and fatigue

Abstract

Steel building and bridge connections have traditionally relied on either bolts or welds only to carry the required load from member to member. Due to the historical use of bolts or welds only, the combination of bolts and welds (referred to as the combination connection) is sparsely utilized in steel structures. However, it is apparent that knowing the behavior of these connections would extremely benefit existing infrastructure. In new construction, especially large structures, fit-up problems may occur and combining bolts and welds may be an economical solution to solve these problems. Unfortunately, neither research nor historical findings can provide the proper guidance as to how these connections can be treated in all situations. This study investigates the behavior of combination connections (a) in single shear configuration under direct tension monotonic and (b) under high cycle fatigue loading. The experimental study has great significance to both the steel building and bridge infrastructure. Large-scale experimental testing has been performed on 12 single shear joints in direct tension monotonic and 1 double shear joint under high-cycle fatigue. The single shear testing program evaluated the influence of weld to bolt ratio, weld location, and installation techniques when both slip-critical bolts and welds are used. An experimental fatigue test was conducted to aid in the categorization of the fatigue behavior of combination connection under AASHTO LRFD bridge design specifications. Accordingly, this experimental study supports the implementation of combination connections given the better characterization of their behavior under various loading conditions.