DAVID BEHAR
Design of the existing pontoon
I began analyzing the plans of the Suffren de Bailly that were made available to me. These plans are those of the old vessel. Thanks to them, I was able to visualize the existing structure of the pontoon, including its dimensions, characteristics, and general configuration. This information was essential for guiding my design and modifications to ensure the seamless integration of the excavator and optimize the efficiency of the work to be carried out. The plans also allowed me to identify the constraints and opportunities related to the pontoon's layout, thus providing me with a solid foundation for developing appropriate technical solutions.
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After designing the pontoon almost identically, as some elements were not useful or were going to be removed, I was able to start creating the reinforcements that would fit inside the pontoon.
HEB reinforcement
To reinforce the internal structure of the pontoon, HEB beams were chosen for the following reasons:
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High structural strength: The H-shaped profiles allow them to support significant loads, ensuring the stability and strength of the pontoon structure. Furthermore, they have a reasonable weight for the strength they provide.
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Efficient load distribution: Due to their shape, they efficiently distribute loads over a larger area. This reduces local stresses and improves the strength and durability of the structure.
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Compatibility with manufacturing methods: HEB profiles can be easily cut and welded, which facilitates their integration into this project.
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Standards and certifications: HEB profiles comply with international standards, such as EN (European Norm) and ASTM (American Society for Testing and Materials) standards.
The HEB beams are made of S235JRG2 steel, commonly used in the naval industry for the following reasons:
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High mechanical strength (235 MPa), enabling it to withstand significant loads and resist the stresses encountered in water. Appropriate coatings and surface treatments can be applied to enhance its corrosion resistance and extend its lifespan.
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Weldability: This steel is well known for its ease of welding, allowing for strong and reliable assemblies.
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Ductility: It offers good ductility, meaning it can undergo a certain amount of plastic deformation before breaking. This characteristic is important because structures must be able to withstand dynamic loads or impacts. This will be the case when the excavator is on the pontoon.
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Availability and cost: It is widely available on the market and at a relatively affordable cost.
Square section tube
Stanchion
Inside the pontoon, there was already a reinforcing structure with stanchions, allowing for the attachment of additional reinforcements. There were also square-section tubes welded with gussets to further enhance the stability of the transom.
The truss beam method is used, which involves a structure of welded HEB beams in a cross-V and V-shape configuration to reinforce (reduce deformation and deflection of the structural elements) and stabilize the structures. Positioning them in this way improves their ability to withstand static and dynamic loads compared to a vertical orientation. Cross-V welded HEB beams are placed in strategic locations where additional stiffness and strength are required due to forces in multiple directions. Conversely, V welded HEB beams are placed in locations where less strength is needed. These HEB beams will primarily experience vertical forces, unlike HEB beams positioned laterally, because the excavator's path is centered.
The HEB beams will be welded to the existing structures and to each other. The method used to ensure this connection involves graphically determined angular material removal, thus creating bearing surfaces for a solid and stable assembly.
Guardrails and work gates
On a pontoon, safety regulations require the installation of guardrails and removable work gates to allow work to be carried out in different configurations. For example, to port, to starboard, alongside, or even while pushing against another boat/pontoon. The guardrails from the old boat (Bailly de Suffren) were retained and reinstalled on the pontoon.
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For dismantling the railings, I created a small system:
It consists of a plate that is welded to the pontoon, and onto which a cylinder is welded. The railing is then placed around the cylinder; this is done, not the other way around, for watertightness. If the cylinder were hollow, dust could get trapped inside. A gap is provided between the blue cylinder and the yellow plate to allow for adjustment of the tube's angle during welding. This flexibility is necessary due to the unevenness of the pontoon's upper surface, which is not perfectly flat. The railing is held in position by a nut and bolt that fits into a hole passing through both the railing and the cylinder.
Once the railings were modeled, I positioned them on the pontoon to determine the required quantity and designed the gates, planned for each side of the pontoon to allow technicians to move freely around it. During the design phase, the goal was to reuse as much of the existing railings as possible, as well as the cylindrical blanks for the demountable system.
Stairwell and staircase
The construction site will reuse the spiral staircase recovered from the original pontoon to reach the lower deck (technical room).
To begin, I determined the location and dimensions of the stairwell opening, that is, the space reserved for the staircase. Furthermore, I took into account the need to create a room with a door to protect the staircase.
Hopper
By positioning it along the starboard edge of the pontoon, the excavator will be able to rotate when centered and avoid colliding with the equipment on the pontoon. The hopper is a 2000 mm square, positioned 425 mm to starboard and 1900 mm to port of the pontoon, due to the pontoon's interior dimensions and to allow clearance for the guardrails.
Finally, I designed the spiral staircase consisting of 11 steps.
Local
An access chamber will be installed within the hopper to facilitate entry. This chamber will be constructed using welded S235JRG2 steel sheets. The sheets will be cut and fitted to the appropriate dimensions, then welded to the existing pontoon structure. To reinforce the chamber, 50 x 70 mm angle brackets will be used. These brackets will provide additional support and help maintain the structural integrity of the chamber. They will be fixed at regular intervals of 500 mm (marine standard).
The four metal sheets will be reinforced by welding a band of flat bar (100 x 6 mm) all around, thus securing them in place. This band plays a crucial role in the strength and stability of the building's structure. It helps minimize deformation by distributing loads and stresses over a larger area, thereby increasing the overall strength of the structure. Furthermore, the band provides additional protection by creating a watertight seal around the building, preventing water infiltration.
The premises will have the following dimensions:
Bollards
The position of bollards on a boat is regulated; it ensures the safety and maneuverability of the vessel during mooring and towing operations:
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Force distribution: The correct positioning of the bollards allows for a balanced distribution of tensile forces, thus minimizing the risk of excessive deformation or failure of the structures.
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Stability and balance: By positioning the bollards symmetrically and in a balanced way, we promote the stability of the ship during mooring and towing maneuvers .
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Ship control: Maintaining ship direction with precise adjustment of the mooring or towing angle.
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Load distribution: When mooring in conditions of strong wind, swell or current, where variable loads may be exerted on the bollards.
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Accessibility and ease of use of mooring lines or cables from boarding points or quays.
For positioning, the bollard (Ref. 9) is centered short (marine standard) with a 500 mm offset, which allows the bollard to remain fixed and prevents it from flexing under the forces during mooring. The bollard is welded to a bracket, which is itself welded to the existing angle brackets of the pontoon. For the design of this bracket, I drew inspiration from another boat. This bracket consists of gussets (Ref. 35), press-fitted reinforcements, and a flat plate (Ref. 34) welded to the flat plate (Ref. 33) and to the pontoon angle brackets. The gussets reinforce the flat plate (Ref. 33), which could flex due to the bollard's weight. The material removed from the flat plate (Ref. 33) allows it to be welded to the bulkhead, thus increasing the rigidity of the bracket.
Partition
The original pontoon (62 m - Suffren de Bailly Pontoon) was cut at the Haute Seine shipyard in Villeneuve-le-Roi. This shipyard converted the main 42 m section into a restaurant. Therefore, they created a bulkhead on the future Marioupol to allow the pontoon to be transported by the Seine. The pontoon thus has an opening that needed to be partitioned. I designed this partition, drawing inspiration from the existing one. The new partition is composed of welded angle brackets and gussets, and 6 mm thick sheet metal. The angle brackets support the different parts of the partition and provide additional mechanical strength. The gussets are welded to the angle brackets and the partition, further reinforcing the structure and preventing the partition from flexing. Material removal allows the partition to be fully embedded in the existing angle brackets and also welded to them.
Existing partition
Location for the installation of the future partition
Corner
100 x 75 x 9 mm
Gusset
Material removal for embedding in the I-beam
Material removal for fixing
