Ship collision on inflatable weirs

Abstract

In the Meuse seven weirs are located in the Dutch reaches, controlling the water level to enable inland navigation through the river. The weirs are being scheduled for replacement, where weir Grave is the first one in 2028. They are reaching their end-of-life time. One of the main issues that became of more importance in the recent years is ship collision. In the past 20 years two major ship collisions happened on two different existing weirs in the Meuse, one at Grave and one at Linne. The place of impact at the weirs was significantly damaged after those collisions. As a consequence, the water level dropped and inland navigation was not possible for one month. In this study an inflatable weir is proposed as replacement of the existing steel weirs in the Meuse. A conceptual inflatable weir design is made for location Grave, for replacement of the existing weir. The design is based on existing literature, such as the inflatable storm surge barrier Ramspol. The design for Grave is considered to be scalable to the overflow (Poirée) parts of the Meuse weirs. One of the aspects that has not yet been considered for those inflatable weirs is ship collision. The theory and formulas found for the existing collision analysis are not fully applicable to the inflatable weir, mainly due to large elastic deformation of the inflatable weir. In literature a standard expression has been found to quantify the ship force on the colliding structure. This expression forms the basis of the analytical model. The inflatable weir in the analytical model is schematized by a two-dimensional plate sheet. An effort was made to validate the strain found in the analytical model by a numerical model in Ansys. However numerical instabilities were found that lead in considerable modification of the desired model and so the results indicated no representative outcomes.
To see what happens during the ship collision a physical scale model was made, with scale 1:25 for accurate representation of the physical phenomena.
Sixteen experiments were done with four different draughts and four different velocities of the ship. For the experiment with the scaled maximum draught (0.14m) and velocity (1.1m/s). The full video experiments are uploaded to the 4TU-datacentrum (https://data.4tu.nl/portal). The two aspects uplift of the ship and gliding over the weir observed in the experiments are not yet included in the analytical model, therefore the analytical model is extended. The extended analytical model showed a 25% deviation with the uplift of the ship and a 15% deviation with the displacement of the weir from the experiments. With the extended model it was calculated that the limit strain is not exceeded and that the strain is maximum 5% on top of the static strain of 1.9%. Concluding, the first steps have been taken into research of ship collision on inflatable weirs. Further investigation on the ship with V-bow, the propeller of the ship and a more extensive numerical model is recommended for ship collision on inflatable weirs.