Analysis of berthing structures for wave induced forces

Abstract

Countries surrounded by ocean can easily achieve tremendous progress in trade and industry provided proper planning of ports and harbours is made for transportation of goods and materials through sea transport. Berthing structures are to be designed for different load combinations. The deck of berthing structure is generally supported by vertical piles. Marine and offshore structures are subjected to wave and current forces and the loads acting on the member are cyclic and will induce time varying forces and moments. Due to this nature of wave forces and moments, the stress in the structure material fluctuates with respect to time, leading to progressive growth of cracks and they ultimately lead to fracture. This fatigue changes depends upon the wave action. To reduce wave and berthing forces, it is important to fix the alignment in such a way that incoming forces are minimum. Berthing structures are the facilities constructed in ports for berthing and mooring of vessels, for loading and unloading of cargo and for embarkment and disembarkment of passengers or vehicles. The berthing structures are designed for dead load, live load, berthing force, mooring force, earthquake load and other environmental loading due to winds, waves, currents etc,. In the present study layout of jetty for berthing 5000 DWT ship at NMPT is modeled using the ship dimensions from IS code and analyzed for the available environmental data from NMPT using StruCAD 3D software. The detailed analysis of the berthing structure for the significant wave height of 3.2m is carried out for a full cycle of wave and the Variation of deflection, forces and moments for perpendicular wave directions and different pile diameters is done by Static and Dynamic analysis. Dynamic Amplification Factor is calculated by comparing static and dynamic analysis results. Time history analysis is also done for the wave loading and deflection, forces and moments of the structure is calculated. From the results it is observed that the forces and moments are large as the diameter of pile increases and the deflection is reduced. From the time history analysis it is observed that as the pile diameter increases the maximum deflection occurs at the larger time period. It was found that at time period of 8.611sec peak response occurs. 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.