Effects of washer geometry, tightening torque, and bolt preload relaxation on the shear-out failure of single bolted pultruded GFRP/steel joints

İngilizce (OpenAlex)

Bolting is one of the most commonly used jointing techniques for assembling pultruded glass fiber-reinforced polymer structures. The performance of bolted joints varies significantly depending on several parameters, including sectional geometry (angle or plate), bolt diameter, tightening torque, and washer geometry. In this study, an extensive experimental program comprising 62 tensile tests was conducted to investigate the effects of these parameters on the performance of single-bolted joints with limited end distance to the hole center. Additionally, the impact of bolt preload relaxation on composite bolted joints was examined. Load–displacement behavior, ultimate load capacity, stiffness, and failure modes were comparatively analyzed. The test results revealed that sectional geometry, tightening torque, and washer geometry have a substantial influence on the joint performance. Furthermore, based on the limited test data, it was observed that the use of smaller bolt diameters may enhance the shear-out strength of single-bolted joints, and even when the initial bolt preload relaxes over time, joint stiffness improves and ultimate capacity remains largely unaffected.