Dynamic Response And Failure Criteria For Hull Structures Under Impact Pressure Considering Strain Rate Effect

Ship structures are likely subjected to “impact pressure” loads due tosloshing, slamming and green seas while in service. Impact pressure andstructure response have become an important part in safety assessment ofships in voyage. In current class rules, the design criteria for dynamic orimpact pressure loads are in principle based on quasi-static equivalenceconcept, with no considerations regarding duration time of impact pressureloads or impulse. The present paper develops failure criteria of ship typicalstructures against hydrodynamic impact pressure and compares them withcurrent class rules’.Formulas considering strain rate effect of material and duration timeof impact pressure loads are proposed for calculating the maximumpermanent deformation of hull panels or stiffened plates against impactpressure and they are examined using LS-DYNA. The correspondingdeformation failure criterions are then proposed according to the conceptof limit state design in comparison with current rules’. Furthermore, theinfluence of shape and duration time of impact loads on structure responseis discussed and the determinant of maximum deformation in the field ofimpulse is summarized. A practical way from related articles for convertingloads is proposed.When the pressure impulse is relatively large, transverse frames may also fail. In this case, the grillage may be idealized as an orthotropic plate.A formula considering strain rate effect of material and critical durationtime of impact pressure loads is proposed for calculating the maximumpermanent deformation of grillages under impact pressure and it isexamined using LS-DYNA. The corresponding deformation failurecriterion is also proposed according to the concept of limit state design incomparison with the panel failure criterion and the stiffened plate failurecriterion.