Hot Spot Stress Analysis In Girth Butt Weld Of Cast Steel Joint Under Eccentric Load

In recent years, the cast steel joints have been widely used as a result of moreand more constructions of novel space structural systems, long-span bridges and deepsea platforms. The cast steel joints generally have a larger thickness than the tubesattached. The different thickness will evidently lead to the stress concentration andweaken the fatigue performance around the weld. At present, there isn’t any domesticcode or standard to specify the fatigue behavior of the cast steel nodes.The theoretical analysis on the fatigue performance of the girth butt weld whichconnects the cast steel joint and the tubes is carried in this paper. The theoreticalresearch and fatigue lifespan estimation of fatigue performance of girth butt weld incast steel joint was conducted based on the hot-spot stress extrapolation method inthis paper, considering two kinds of load conditions, bending moment loads andcomposite action of axial force and bending moment loads. The results show that thelocation of hot-spot stress of two kinds of weld details is at the weld toes. Parametricanalysis are carried out on the thickness (t) of steel tubes, the ratio of tube’s diameterto its thickness (d/t) and the ratio of cast steel joint’s thickness to tube’ s (T/t). DNVhave recommended the method to predict weld fatigue life. The method can be usedto predict the residual fatigue life when the weld is under axial force and bendingmoment. To predict the fatigue life of two kinds of welding details, the hot-spot stressconcentration factors and the S-N curves should be used.The results show that the hot-spot stress concentration factor has littlerelationship with the thickness of tubes (t), but increases with the d/t increment;additionally, the hot-spot stress concentration factor decreases with the T/t increment.The medial transition welding details have a better fatigue performance than the oneswith outer transition.