PIANC Smart Rivers 2022

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Abstract : *(250~1000 words)

The design of lock gates requires to account for accidental limit states, in which ship impacts shall be considered. Such analyses are not always straight forward. This problem is generally approached in two different ways: firstly, by the use of an equivalent static method, in which the impact is modeled by a quasi-static force, or by the use of dynamic numerical simulations, during which the progress of the ship and the temporal evolution of the impact force is taken into account. The second approach requires extensive calculation and modeling efforts, which are generally prohibitive in the early design stage. Such analyses are therefore justified only at the final stage of design. Therefore, the objective of this research is to develop a calculation tool based on analytical methods to circumvent these difficulties and allow the consideration of ship collisions in the early design phase of lock gates.

These analytical developments are based on the super-element method, described by Lützen et al., in which a structural element is modelled by its geometric and mechanical properties. This methodology is used to first, evaluate the resistance of the lock gate in local deformation mode, assuming that there is only crushing of certain structural elements in a limited zone, located in the close vicinity of the impact. Then, to calculate the entire resistance of the lock gate for which the global deformation mode is considered, assuming a bending of the entire structure. Thanks to this analytical procedure, the evolution of the impact force according to the penetration of the ship can be evaluated with a good accuracy.

This method has already been applied by L. Buldgen, T. Pire and S. Echeverry for collision of boats with lock gates and collision on fixed or floating wind turbines. These developments are used as the basis for current research. The scientific objective is to extend this approach to lock gates, which cannot currently be treated, in particular those where the layout of the stiffening elements can be highly irregular. This implies to take into account the global deformation of the structure, because the current method is not suitable for strongly orthotropic structures.

In this regard, additional developments are currently underway in the framework of the Belgian COLLFOWT project, within the GREENWIN cluster, in partnership with the University of Liège and SBE, an engineering company specializing in this field.

References

Buldgen, L. 2014. Simplified analytical methods for the crashworthiness and the seismic design of lock gates. PhD thesis, Faculty of applied sciences, University of Liege, Belgium.

Echeverry, S. 2021. Numerical and analytical study of a spar-like floating offshore wind turbine impacted by a ship. PhD. thesis,  Faculty of applied sciences,  University of Liege, Belgium.

Lützen, M., Simonsen, B.C., Pedersen, P.T. 2000. Rapid prediction of damage to struck and striking vessels in collision event. Proceedings of Ship Structure Symposium for the New Millennium: Supporting Quality in Shipbuilding, Arlington, United States.

Pire, T. 2018. Development of a code based on the continuous element method to assess the crashworthiness of an offshore wind turbine jacket. PhD thesis, Faculty of applied sciences, University of Liege, Belgium

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