PIANC Smart Rivers 2022

Reviewing Presentation documents

Topic:

Title:

Author(s):

Author 1

Name：

Affiliations：

Region：

Email：

Is corresponding author or not (one only)：

Author 2

Name：

Affiliations：

Region：

Email：

Is corresponding author or not (one only)：

Author 3

Name：

Affiliations：

Region：

Email：

Is corresponding author or not (one only)：

Abstract : *(250~1000 words)

During the filling and emptying process of a navigation lock the vessel in a lock chamber is exposed to forces acting on the hull. These forces accelerate the vessel and lead to a displacement. To avoid a collision of the vessel with the lock structure, it is moored with mooring lines. These lines can be strained up to a certain breaking load. The force acting in the mooring lines is called the hawser force and must be distinguished from the ship force. If the hawser force exceeds the breaking load, the mooring line will fail and the tension energy will abruptly be transformed into kinetic energy. A snap-back of the mooring line ends can produce great forces and the mooring staff is at highly risk for major injuries. Thus, the hawser force must be limited during the locking process.

Typically, acting forces on the vessel are determined via experimental and numerical modelling techniques because this force is reproducible and does not depend on the mooring line specifications. In most countries standardization laws are available defining maximum vessel forces. In Germany these force limits were developed on the basis of analytical worst-case estimations in the 1980s combined with little practical considerations. These limits might be too conservative since the practical experience shows only a very small number of accidents due to breaking mooring lines. Thus, a research and development project at the Federal Waterways Engineering and Research Institute was started to find more reliable limit values which are scientifically proven and fit to modern design concepts.

The magnitude of the hawser forces depends on the hydraulic forces acting on the vessel and among others on the spatial arrangement of the mooring lines; the length, the pretension and the spring constant of the lines. These mooring line specifications depend on the so called “human factor”, practical considerations and the mooring line’s general condition. Due to its randomized character it is impossible to specify all these factors and to define a general transmission function from ship force to mooring line force.

In order to address these existing uncertainties a safety concept following the example of modern semi-probabilistic design concepts was developed which allows to distinguish between uncertainties on impact and resistance side. The focus of this work will be on the evaluation of the impact side. A mooring model was developed which allows transient simulations of the mooring line behavior depending on the forces acting on the vessel and a set of mooring line specifications. Monte-Carlo simulations were conducted to find a statistical distribution of the mooring line forces regarding the variety of possible mooring line and ship force specifications. From the results of these simulations an amplification factor can be defined which denotes the maximum mooring line force based on the force acting on the vessel. This approach will allow to determine the maximum force action on the hull based on a modern safety concept.

Key words: (max: 5)

Reference no.

Slides：

click to download