This study examines the fatigue performance of tubular joints fabricated using a new type of enhanced partial joint penetration weld details under constant-amplitude brace in-plane bending actions. The numerical study ascertains the crack propagation angle, the crack-front profile and the interaction between adjacent cracks on the stress-intensity factors. | Vietnam Journal of Mechanics, VAST, Vol. 35, No. 1 (2013), pp. 67 – 77 FATIGUE PERFORMANCE OF TUBULAR X-JOINTS: NUMERICAL INVESTIGATION Nguyen Chien Thang1 , Qian Xudong2 , Ton That Hoang Lan3 1 Duy Tan University, Da Nang, Vietnam 2 National University of Singapore 3 University of Architecture, Ho Chi Minh City, Vietnam Abstract. The cyclic actions due to waves, currents and winds on offshore platforms frequently cause fatigue cracks at hot-spot locations. The remaining fatigue life of such connections depends significantly on the fatigue driving force often measured by the stress-intensity factors. This study examines the fatigue performance of tubular joints fabricated using a new type of enhanced partial joint penetration weld details under constant-amplitude brace in-plane bending actions. The numerical study ascertains the crack propagation angle, the crack-front profile and the interaction between adjacent cracks on the stress-intensity factors. Keywords: Fatigue, tubular X-joints, crack propagation, SIF, finite element model. 1. INTRODUCTION Fatigue failure caused by the initiation and propagation of surface cracks near the hot-spot weld-toe locations imposes a critical threat to the safety of offshore structures and onshore bridges experiencing cyclic actions throughout their operational lives. The fabrication of welded components in these structures should therefore entail a convenient profile with high quality controls, which satisfy the fatigue requirement prescribed in design codes [1]. The complete joint penetration (CJP) welds, widely implemented in offshore jacket structures, require highly skilled workmanship in delivering quality welds meeting the code requirement [1]. The potential defects near the open root of the CJP welds may lead to detrimental failures of the platform under fatigue loads [2]. Qian et al. [2] proposed a new type of welding details, namely the enhanced partial joint penetration (PJP+) welds, which include a part of the .
