Experimental study of slip-resistant connections under cyclic load

The slip-resistant shear connections with preload bolts have traditionally use in the steel structures exposed to cyclic / fatigue loading or in the cases when the bolt slipping or connection deformations should be restricted. Hence, the shear load is transferred through the friction surfaces rather than the contact between bolt surface and hole. The main influencing parameters determine the connection slip resistance are the friction between the contact surfaces and the level of preload in the bolts. This paper presents an experimental study of preloaded bolted connections under cyclic load. Experiment was performed on double lap shear connections using high strength bolts and lock bolts, both M20 of grade 10.9. The steel plates used in experiment are grade S355JRG2. Sandblasting was performed using quartz sand as the abrasive after which the zinc-silicate coating was applied on plate surfaces. To address the required pretension force in the bolts, the strain gauge method was employed. All strain gauges were calibrated. Six specimens were exposed to cyclic loading after monitoring initial and short-term losses of pretension forces in the bolts. The main objective of the presented study is to investigate the influence of the cyclic load on the losses of pretension force in high strength bolts and lock bolts. The results of comparative experimental analysis are presented and discussed. © 2021 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.