Experimental study of both bending moment and preload effect on the stress cycle upon bolts in a tee-stub

Abstract

The experimental study exposed in this paper aims to exhibit the effect of the bending moment and the preload on bolts. A bolted tee-stub connection defined in Eurocode 3, part-1–8, is used. The flanges of the tee-stubs are taken from IPE400 and HEB 320 beams. The HR-M12-10.9 bolts are used and are equipped with four strain gauges each. The strains measured lead to calculate the axial load and the bending moment in the bolts. Six different configurations of the tee-stub are tested. For each configuration, four preload values have been studied. These tests provided an opportunity to take a critical look at the true value of the axial force and the bending moment in the bolt. We noted the existence of out-of-plane bending moment. Despite the existence of out-of-plane bending, it was seen through the results that the increase in the preload value causes a reduction in the amplitude of the stress cycle on the bolt. The percentages of the reduction due to the preload are greater for rigid flanges and smaller for flexible ones. As the amplitude of the stress is the main fatigue failure factor, its reduction shows that preload is beneficial for the fatigue resistance of such joints.