Samenvatting

Barges are used in order to transport all types of offshore structures and equipment. Structures which are transported are becoming larger and heavier. Therefore, there is need for barges that can handle these structures. This research will explore the possibilities to increase barge capacity by adding a secondary deck.
This research includes a comparison between a typical web frame 13 of the H-541 and an alternative design of a web frame. The goal of this research is to improve web frame capacity and global capacity of a typical web frame 13 by adding a secondary deck to the deck beams, and increase the web height of the deck beams. The reason to check this typical web frame over other the typical web frames is that the web height of the typical web frame 13 is continuous over the entire length of the deck beam.

Adding a secondary deck will result in a significant increase in weight. Not only will the secondary deck contribute to the addition of weight but also the stiffeners which are required in order to prevent buckling of the secondary deck. In order to compensate for the increase in weight, material from another section of the web frame will be removed. The section which will be removed are 2 particular columns of the web frame. By removing 2 columns, the dimensions of the deck beams will change, creating relatively large bending moments. In order to avoid these relatively large bending moments, 2 columns will be re-positioned.

During this research hand calculations are made for the conventional web frame 13 and the alternative web frame 13. These calculations are made in order to check web frame capacity. After calculations by hand, a SACS model is created for the alternative web frame 13. With this SACS model, the web frame capacities of the alternative web frame are determined and compared with capacities of the conventional web frame.

Global capacity of the conventional and alternative web frames are made using a excel spreadsheet in order to determine the allowable bending moment and the allowable shear force.

Hand calculations show that mid-beam capacities of the alternative web frame have decreased. The capacity near the support point of the beam have increased due to the increase of web height (therefore reducing shear stress).
The SACS model shows that capacities of the alternative web frame have decreased as well. Primarily half way the beam sections, capacities have decrease because the span of the deck beams has increased. The increase of span creates larger bending moments and therefore increases bending stress. However, capacities of the deck beams near the brackets and columns have increased due to adding the secondary deck and the increase of web height.

According to the calculations on the global strength of an alternative typical web frame 13, the global capacity will decrease. The allowable shear force will decrease as a result of removing 2 columns (and therefore also 2 longitudinal bulkheads). As a result of the shift of the distance from the neutral axis to the outer fiber of the bottom plating, the allowable bending moment will decrease as well.
Further research on adding a secondary deck should be done in order to increase web frame and global capacity of a typical web frame 13.