Influence of load shape on dynamic response of cross-stiffened deck subjected to in-plane impact

摘要

Under severe sagging condition or wave slamming, ship deck is dynamically loaded in nature with impact type load. Based on the nonlinear explicit finite element method, the paper aims at studying influence of load shape on dynamic response of a cross-stiffened deck subjected to in-plane impact, accounting for strain rate effect, strain hardening, and potential contact of compressive components. Axial residual displacement of the impacted end is selected as main detected dynamic response of the deck. Four parameters depicting load shape are considered; they are impact duration, peak load, the decaying type after reaching the peak load (here refers to second order derivative of the load), ratio between rise time of the load and total impact duration. The first three load shape parameters, impact duration, peak load and decaying type, are related to impulse. The longer the impact duration, the larger the peak load, the slower the decaying of the load, which can result in the larger impulse. The larger the impulse is, the larger the dynamic response of the impacted deck is, on the condition that the impact duration is finite with the order of milliseconds. While the fourth load shape parameter, ratio of rise time and impact duration, although it is not related to impulse, it is also an important influential factor on dynamic response of the impacted deck. The smaller the ratio of rise time and impact duration is, the larger the dynamic response of the impacted deck is; if the impact duration is longer, the effect is more significant. So the parameter, ratio of rise time and impact duration, deserves more concern in future research.