The first-generation cracks around the slot cut-out were at the connection of the web stiffener to the longitudinal stiffener. It was found that in addition to the insufficient scantling of web stiffeners, shear force on the primary supporting member caused tensile stress between the web stiffener and the longitudinal stiffener, and that depending on the direction of the slot cut-out, it superposed the local stress exerted by the longitudinal stiffener. One of the most effective countermeasure was to add collar plates. The second-generation cracks were characterized by the propagation into the longitudinal stiffeners. Application of higher tensile steel and L shaped longitudinal stiffeners resulted in increased stresses, and caused the cracks. Counter-measures were to decrease stress by increased scantling and application of T shape to the longitudinal stiffeners, and soft heel and toe of the web stiffener at the connection to the longitudinal stiffener. Nowadays, even though all the countermeasures for the first and second-generation cracks were taken, small number of cracks are still sometimes observed around the slot cut-out. We call this the third-generation cracks, and investigated it through finite element analysis. In this paper, we outline the characteristics of the third-generation cracks, and review CSR-O/T about its effectiveness.
展开▼
