Numerical analysis of SCF of Tubular T-joints strengthened with prestressed CFRP

Abstract

Fatigue failure is one of the main concerns of welded tubular joints owing to inevitable welding defects and severe stress concentration along the intersection. In addition, the complex geometry of the joint makes it inconvenient to reinforce by traditional repair methods. Carbon fiber-reinforced polymer (CFRP) composite has been widely used for structural strengthening due to superior strength-to-weight ratio, good fatigue and corrosion resistance, as well as ease of installation. Although tubular joints strengthened by using non-prestressed CFRP sheets have been investigated in references, application of prestressed CFRP has not been reported. This study proposed a form of prestressed CFRP sheets for the fatigue strengthening of tubular T-joints. Three-dimensional finite element models were developed for both CFRP-strengthened and unstrengthened tubular T-joints to calculate the hot spot stress distribution, which was verified using experimental test data and Lloyd’s Register (LR) equations. A parametric study was then carried out to explore effects of CFRP strengthening parameters on the SCF reduction coefficient ψ, including the prestressing level (p), CFRP width (w), and CFRP layers (n). It was found that prestressing CFRP changed the stress distribution and values along the weld toe. With the increase of prestress, the position of the maximum stress gradually moved from the saddle point to the crown point. Besides, the strengthening parameters had significant effects on reduction of the hot spot stress along the weld toe.