IHB Ship Design в числа – 15 години опит, 80 инженери, 400+ завършени проекта
1. Main outline of the project
Lashing bridge structures enable lashings to be attached to containers high up in a stack. They give stacks lashed in such a way greater stability and allow higher total loading capacities to be achieved. The project is modification of four lashing bridges of a 6500 TEU Container Carrier. The modification was needed in order to allow for one more tier of containers on the corresponding bays.
The project consists of an upgrade of the Lashing arrangement in the aft, including:
The modification was performed on 4 lashing bridges situated above Cargo Hold 8 in the aft part of the vessel. Lashing bridges were extended up by the height of one container as shown in green in the picture below:
2. Strength calculations
As part of the design, FEM strength calculations were performed to evaluate the design. In this case study, we are showing the calculations necessary for evaluating the design. Calculations were performed for all four Lashing bridges, in this case, we are showing the results for one of the four modified Lashing bridges.
Geometry of the modified Lashing Bridge
Mesh discretization of Lashing Bridge
Loading in the lashing eyes was specified by the Customer to be 176kN for the upper lashing and 189kN for the lower lashing. Forces are valid for 6.57m GM, combined with max. reachable stackload and low CG of the stack.
Loading of Lashing Bridge
Calculation model – Deformation
Calculation model – Equivalent stress
Total deformation is within the specified limits.
Values for both Equivalent Stress and Maximum Shear Stress are generally below the allowable stress limits (204MPa for Equivalent Stress and 94MPa for Shear Stress). Areas, where calculated stress is above the allowable limits are very small. Peak extreme values decrease fast to acceptable values. Therefore, those are considered to be non-physical and can be ignored.
Calculations show that the modified Lashing Bridges comply with the requirements.