Abstract: Eight 10×104 m3 crude oil storage tanks were constructed in one project. After water filling test of the tanks, it was found that the weld toe near the bottom plate of the large fillet weld inner side of #T13 tank cracked locally. This paper introduces the cracking of the fillet weld and the settlement deformation of the tank bottom plate during water filling test. It analyzes the residual stress in multi-layer and multi-pass welding of T-Welded joint and the additional stress in the fillet weld inside T-joints during water filling process. According to this, the paper established the basis of judgment for the cracking of fillet weld inside T-joints of storage tanks. And it is considered that the ring beam settlement plus welding residual stress caused stress concentration at the weld toe near the bottom plate of the inner side of the large fillet weld. Thus the local stress exceeded the tensile strength of steel plate, which was the main reason for the cracking.

Key words: storage tank, bottom plate, ring beam settlement, welding residual stress, large fillet weld, stress concentration, cracking