A BOUNDARY ELEMENT ANALYSIS OF NON-LOAD-CARRYING CRUCIFORM WELDED JOINTS STRENGTHENED WITH FRP MATERIALS

摘要

Fibre reinforced polymer (FRP) materials have been employed to improve fatigue strength of steel structures. In this study, boundary element technique is employed to calculate stress intensity factors (SIFs) during the crack propagation phase of nonload-carrying cruciform joints un-strengthened or strengthened with FRP materials. Reduction of stress intensity factors is clarified for specimens patched with FRP materials. Thereafter, fatigue life is estimated with NASGRO equation, which is modified from Paris law. It is observed that the fatigue improvements agreed with existing experimental results. This indicates the fatigue strength can be upgraded with appropriate strengthening of FRP materials. The effects of various strengthening parameters on the fatigue lives are also presented. It is indicated that single sided patch on cracked surface is beneficial than double sided repair. Increase of modulus of FRP materials and adhesive can achieve better fatigue performance. More layers of patch have a positive effect while the increase of adhesive thickness has a negative effect on fatigue life.