Evaluating lock gates' strength due to ship collisions: A Douro waterway lock gates case study

Abstract

This paper presents a crashworthiness case study where is evaluated the Douro river lock gates' strength due to ship collisions. The increasing traffic in the Douro waterway and the prospect of reopening the Moncorvo iron mines have settled the conditions for starting the preliminary works on the modernisation of the waterway. Since the construction of the Douro river lock gates, the mass of the ships navigating the waterway have increased from a maximum of 2200 tons–2900 tons, so the evaluation of the lock gates' crashworthiness to ship impacts needs to be updated to the current navigation conditions. A methodology to solve the impact problem is firstly defined in terms of simulation type, geometry definition, impact location, material model and contact model, taking into account the procedures in [9]. This methodology is then applied to the Carrapatelo upstream lock gate and using the Abaqus/Explicit solver, finite element dynamics simulations were performed to evaluate the response of the lock gate to impacts by two different ships at variable water levels. The greatest risk associated with the impacts is pondered to be the possibility of the gate falling into the lock chamber, or that its deformation is enough for a large mass of water to fall into the lock chamber. In order to evaluate this, a series of criteria that quantify the damage delivered to the lock gate and its supports are defined. The obtained results show that the damage in the lock gate is not sufficient for the occurrence of a hazard with possible loss of life. However, for one of the impact cases, the reaction force on the chains that connect the gate to the electromechanical actuators was equivalent to 3.6 times the expected load from the static weight of the gate, which is believed to be dangerous for the operation of the lock. Finally, the possibility of using an energy dissipating mechanism to reduce the damage in the lock gate is evaluated, and the results show good improvement on that course.