Dynamic Inversion Model of the Mooring Force on a Floating Bollard of a Sea Lock

Abstract

Sea locks that connect inland canals and rivers to the open sea are crucial links that ensure the efficient navigation of ships. Floating bollards (FBs) are significant components of sea locks, and they are affected by factors such as large ships, speed of entry, and irregular mooring lines coupled with corrosion by chloride salts from seawater intrusion from the environment. These factors aggravate damage to metal structures, which seriously threatens the safety of FBs. Overloading of FBs by mooring forces caused by the illegal use of FBs for the braking of large ships that enter locks at excessive speed is the main cause of structural damage and overload failure for FBs. Controlling the dynamic mooring force acting on the FB is an important prerequisite to ensure the safe passage of a ship through a lock. It is impossible to perform real-time monitoring of the magnitude and direction of the mooring force on an FB by installing load-measuring equipment on the mooring line. Therefore, in this study, the structure of an FB in a sea lock project was taken as an example, and the mathematical relationships between the strain in the load-sensitive area of the FB and the mooring force and the mooring angle were quantified. A dynamic inversion model of the ship mooring force on an FB was proposed. This model used real-time feedback from the strain signal in the load-sensitive region of the FB structure to obtain information about the mooring force. The accuracy of the model was verified by conducting tests with a physical model of the topside structure of the FB and comparing the predicted results with the test data. The research results can lay a theoretical foundation for real-time monitoring of the structural response of an FB under the action of mooring forces and promote the development of intelligent methods for the operation and maintenance of a sea lock, which have important scientific significance and engineering value.

An Intelligent Monitoring System for the Force Characteristics of Floating Bollards in a Ship Lock

“…When the height of the ship's freeboard exceeds that of the floating bollard, it will be subjected to upward mooring force, and at this time, the vertical angle β > 0 (see Figure 1a). Conversely, the floating bollard will be subjected to downward mooring force, i.e., β < 0; see Figure 1b [21]. According to the specifications [32] and field measurements [33], β can be taken as 15 • and −15 • in the above two cases.…”

“…Based on the structural type and characteristics of the floating bollard, a structural system composed of a hollow cylindrical body and upper and lower stainless plates is generalized as a hyperstatic linear elastic overhanging beam model with an equal section restrained by fixed bearings. The upper and lower stainless plates are considered fixed hinge supports and fixed supports, respectively (see Figure 2) [21]. There are two test points T and K for structural strain confirmed on the surface of the hollow cylinder column for the floating bollard, as shown in Figure 1d, and the structural strains at the two points of T and K are respectively set as ε T and ε K .…”

“…There are two test points T and K for structural strain confirmed on the surface of the hollow cylinder column for the floating bollard, as shown in Figure 1d, and the structural strains at the two points of T and K are respectively set as ε T and ε K . Based on previous research results from this research team [21], the fundamental theory of mathematical mechanics is used, combined with the generalized geometrical model in Figure 2b,c, the mathematical and mechanical relationships between the strain ε and the mooring force F, as well as the horizontal angle α, are quantified, and the theoretical model of floating bollard load response under the mooring force is proposed as follows: α, are quantified, and the theoretical model of floating bollard load response under the mooring force is proposed as follows: If the mooring angle β > 0, β = 15 • :…”

“…On this basis, a mechanical model of floating bollard load response was educed if the vertical mooring angle β was considered as a positive value, and the precision of the model was proved based on the in situ experimental data in a certain ship lock in China. Wu et al [21] proposed a dynamic inversion model for the mooring force of floating bollards based on the mathematical and mechanical basic theories. This model can convert the strain signal into mooring force information in real-time, and the precision of the model was proved through physical model tests.…”

Failure analysis and Mechanical Behaviour of A60 steel Bollards Used In Port Infrastructure

“…Analysing the given loads, such as mooring forces and ship tension, is critical for knowing the pressure on bollards [9][10][11][12]. In response to these loads, design guidelines and standards have been developed to make sure bollards can withstand the tension from ships as well as the dynamic forces of mooring operations.…”