Investigation of the effect of pre-tightening forces on bolted connection for FRP-steel joints

Abstract

This paper experimentally and numerically investigates the effect of pre-tightening forces on bolted connection for double-lap FRP-steel joints, considering varied levels of pre-tightening forces. In the experimental phase of this study, six bolted double-lap pull-pull specimens with varying pre-tightening degrees (preloaded of 0, 3, 6, 7, 8, and 9 N·m, respectively) were examined. Test results indicated that all specimens exhibited bearing failure of FRP plates and the load capacity was significantly influenced by the pre-tightening forces applied through bolts. The highest loading capacity (27.1 kN) was recorded for the specimen with a preloaded of 6 N·m. In order to study the stress distribution of FRP plate for the bolted specimens, three-dimensional finite element (FE) models were conducted. Based on the FE analyzing results, the pre-tightening coefficient Pc (the coefficient of the preload increment per pre-tightening torque of bolts) of 750 m−1 was concluded and further proved by the analysis of the stress in contact zones for specimens preloaded by 0, 3, and 6 N·m.

Keywords

• Bolted connection
• FRP-steel joints
• Pre-tightening Force
• Finite element model
• Bearing capacity