At locations where a marine structure needs to service Roll On / Roll vessels, special ramp structures need to be built to make sure the cargo of these vessels can safely enter and exit the vessel onto the quay wall at all water levels, or at least for the majority.

RoRo vessels, which are designed to carry wheeled cargo such as cars, trucks, and trailers will have their own vessel ramp but that needs to be compatible with the ramp on shore.

Designing and constructing these structures involves considering various factors, such as ship characteristics, environmental conditions, and safety. Careful planning, design, and maintenance are essential to ensure their long-term reliability and efficiency.

This blog post provides a comprehensive guide to Roll-on/Roll-off (RoRo) ramps, linkspans, and walkways, which are crucial components of marine transportation infrastructure. It explores the key aspects of their design, operation, and maintenance, covering topics such as types, design considerations, geometry requirements, structural design, materials, case studies, and future trends.

Types of Vessel Ramps

It is important to understnd the different types of vessel ramps that RoRo vessels will have. Below shows the four main types – the stern ramp hoiwever is by far the most common and especially with smaller RoRo vessels.

source: https://porteconomicsmanagement.org/pemp/contents/part3/bulk-breakbulk-terminal-design-equipment/ramps-roro-vessels/

Types of RoRo Ramps and Linkspans

Together, linkspans and walkways enhance the versatility and efficiency of RoRo port operations, enabling them to handle a wide range of vessels and passenger volumes in various environmental conditions.

RoRo ramps, linkspans, and walkways differ from other marine structures as they enable direct loading and unloading of vehicles and passengers without the need for cranes or lifting equipment. This streamlines the process and reduces the risk of cargo damage during handling.

For modest tidal ranges, a RoRo amp on the qua wall will be sufficient but when the tidal ranges are more sever a special linkspan might be required.

Fixed RoRo ramps

RoRo ramps are fixed structures that connect the shore to the vessel's ramp or deck, allowing vehicles to drive directly onto or off the vessel under their own power. They are designed to accommodate specific requirements of RoRo vessels, considering factors like tidal variations and vessel size.

source: https://sms-sme.com/sub2-1.php

Linkspans (lifted, pontoon, and semi-submersible types)

Linkspans and walkways are essential when a port needs to accommodate RoRo vessels with varying deck heights or those operating in areas with significant tidal ranges.

source: https://vogen.pl/en/linkspan/

Linkspans provide a flexible and adjustable connection between the shore and the vessel, allowing for smooth vehicle loading and unloading even as the vessel's deck height changes due to tidal variations or cargo weight distribution.

Linkspans are movable structures that can be adjusted to match the height of the vessel's ramp or deck, accommodating tidal changes and vessel movement. They come in various types, such as lifted, pontoon, and semi-submersible, each with unique characteristics and advantages.

source: https://www.mclh.co.uk/project/port-of-felixstowe-dooley-terminal-upgrading-roro-3-4/

Passenger walkways

Walkways, on the other hand, are crucial for ensuring the safety and comfort of foot passengers, particularly when boarding or disembarking ferries. They provide a stable and secure path for passengers to move between the vessel and the terminal, separate from the vehicle traffic on the RoRo ramp.

Passenger walkways provide safe and convenient access for foot passengers boarding or disembarking RoRo vessels, particularly ferries. They come in different configurations, like Type A, B, C, and D (BS 6349-8) depending on the port and vessel requirements.

Design Considerations

When designing RoRo ramps, linkspans, and walkways, several critical factors must be taken into account to ensure optimal performance, safety, and efficiency. These considerations include:

Operational Requirements and Efficiency

  • The design should facilitate quick and smooth loading and unloading of vehicles and passengers, minimizing vessel turnaround times.
  • The layout should allow for efficient traffic flow, avoiding bottlenecks and congestion.
  • The structure should be able to handle the expected traffic volume and vehicle types, considering future growth and changes in cargo mix.

Ship Characteristics and Compatibility

  • The design must be compatible with the specific RoRo vessels that will use the facility, taking into account factors such as ramp width, deck height, and vessel size.
  • The structure should be able to accommodate a range of vessel types and sizes, providing flexibility for future changes in the shipping industry.
  • The interface between the ship and the shore-based structure should be carefully designed to ensure safe and seamless transitions.

Environmental Factors (tides, currents, waves, and wind)

  • The design must consider the local tidal range and variations, ensuring that the structure can operate effectively at all water levels.
  • Currents, waves, and wind loads should be accounted for, as these can impact vessel movement and stability during loading and unloading operations.
  • The structure should be designed to withstand the harsh marine environment, including corrosion, abrasion, and marine growth.

Safety and Emergency Access

  • The design should prioritize the safety of vehicle drivers, passengers, and port personnel, incorporating features such as non-slip surfaces, guardrails, and clear signage.
  • Emergency access routes and evacuation procedures should be carefully planned and integrated into the overall design.
  • The structure should be equipped with fire protection and life-saving equipment, as well as systems for managing potential fuel spills or other environmental hazards.

By carefully considering these factors during the design process, RoRo ramps, linkspans, and walkways can be optimized for their intended use, providing safe, efficient, and reliable operations for years to come.

Vertical Geometry Requirements

The Vertical geometry is of RoRo ramps, linkspans, and walkway designs is absolutley crucial, as it directly affects the safety and efficiency of vehicle and passenger movement. Proper vertical geometry ensures smooth transitions between the shore and the vessel, minimizing the risk of accidents and damage to cargo.

For something as simple as a ramp – this is time and again the issues that I have seen can cause problems. Here it is key to get an accurate envelope of design vehicles using the facility and to determine if extreme water levels need to be considered or whether some downtime is acceptable.

Here is where the code BS 6349-8 is an invaluable resource for maximum limits, however it leaves the question of extreme water levels over to the designer.

It is important to point out here the difference between the ships own ramps and the ramp of either the linkspan or RoRo ramp.

Typical Ramp arrangement at high water level unladen:

Typical Ramp arrangement at low water level laden:

Factors Affecting Vertical Geometry

  • The design water level variation, which is typically based on the mean high water springs (MHWS) and mean low water springs (MLWS) or the highest and lowest astronomical tides (HAT and LAT).
  • The design should also take into account extreme water levels (up to HAT and LAT) for example which have different limits.
  • The design life is important here as you will need to also make allowances for storm surge and sea level rise over that period.
  • The range of vessel freeboard heights, which can vary depending on the type and size of the RoRo vessels using the facility.
  • The maximum allowable gradients for vehicle ramps and passenger walkways, as specified by relevant standards and regulations.

Maximum Gradients for Roadways and Passenger Walkways

  • Most ship ramps can go up to 1 in 10 (5.7%) upwards or downwards and this is a good start for preliminary design.
  • For roadways, the maximum gradient should not exceed 1:10 (10%) between the design low and high water levels, and 1:8 (12.5%) for extreme tidal and sea state conditions, as per BS 6349-8.
  • Passenger walkways should have a maximum gradient of 1:12 (8.3%) between the design low and high water levels, and 1:10 (10%) for extreme conditions.
  • These gradients are crucial for ensuring vehicle stability and passenger safety, particularly in wet or slippery conditions.

Vertical Geometry Guidelines for Normal Circumstances

  • The vertical profile of the ramp or linkspan should be designed to accommodate the expected range of vessel ramp heights and tidal variations.
  • A smooth transition should be provided between the shore and the vessel, with gradients kept as low as possible within the allowable limits.
  • Where changes in gradient are necessary, transition curves should be used to minimize the risk of vehicle grounding or passenger discomfort.

Transition Areas and Vehicle Grounding Prevention

  • Transition areas, or intermediate gradients, should be provided at changes in gradient and at all locations where relative articulation and movements can occur.
  • These transitions should be designed to minimize the risk of vehicle grounding, taking into account factors such as wheelbase, ground clearance, and vehicle speed.
  • Adequate clearance should be provided between the underside of the ramp or linkspan and the water surface, considering factors such as wave action, vessel movement, and tidal variations.
  • Removable ramps or flaps can be used to provide a smooth transition between the linkspan and the vessel ramp, accommodating any differences in height or angle.

By carefully considering these vertical geometry requirements, designers can create RoRo ramps, linkspans, and walkways that provide safe and efficient access for vehicles and passengers across a wide range of tidal conditions and vessel types.

Horizontal Geometry Requirements

The horizontal geometry is another main input to the design and is going to be a lot easier to figure out than the verticall geometry. The main consideration here is that your design vessels haeve sufficient space to deploy their ramps and durin gloading and offloading, vessel motions are considered so that these can be done safely.

IF youa re also responsible for the design of the topisides, you also need to consider traffic and pedestrian flow for offloading but also during loading and where vessels will park up ready

Plan Geometry Considerations

  • Roadway widths should be designed to accommodate the largest vehicles expected to use the facility, with additional allowances for side clearances and safety barriers.
  • A minimum roadway width of 4.5 meters is recommended for single-lane traffic, while multi-lane facilities should provide at least 3.5 meters per lane, as per BS 6349-8.
  • The ramp or linkspan should be wide enough to accommodate the widest ship ramp expected to use the facility, with additional allowances for ship movement and positioning tolerances.
  • Turning radii and swept paths should be considered for vehicles maneuvering on the ramp or linkspan, particularly at bends or intersections.
  • Pedestrian walkways should have a minimum clear width of 1.2 meters, with additional width provided where high passenger volumes are expected.

Interface Limit Line and Clearances

  • The interface limit line (ILL) is a critical design element that defines the minimum safe distance between the seaward end of the ramp or linkspan and the ship's ramp.
  • The ILL should be positioned to ensure that the ship's ramp can safely rest on the shore-based structure, with adequate clearance for ship movement and fender compression.
  • A minimum clearance of 500mm should be provided between the ILL and the ship's ramp to allow for ship movement and positioning tolerances.
  • Additional clearances may be required for specific ship types or environmental conditions, such as high wind or wave action.

Plan Movements and Predicted Movements of Ships and the Facility

  • The design should account for the predicted movements of ships and the shore-based structure due to factors such as wind, waves, currents, and tidal variations.
  • Ship motions such as surge, sway, and yaw should be considered, along with the resulting movements of the ship's ramp and any connected shore-based structures.
  • The design should also account for the movement of the shore-based structure itself, including deflections due to vehicle loads, thermal expansion and contraction, and long-term settlement.
  • Articulation points and expansion joints should be provided to accommodate these movements and prevent damage to the structure or connected equipment.
  • In some cases, it may be necessary to provide lateral restraint to the ship's ramp to limit its movement and prevent damage to the shore-based structure.

Structural Design and Analysis

The water depth and required arrangement for the quay wall will be the determining factor in the choosing the structure type. The critical design input here will be the vertical geometry and requirements and if you have enough space on land to get the required slopes.

Design Codes and Standards

  • The design of RoRo ramps, linkspans, and walkways should comply with recognized codes and standards, such as BS 6349 (Maritime Works), The Eurocode suite of codes or even theBS 5400 (Steel, Concrete and Composite Bridges), and Lloyd's Register's Rules for the Classification of Linkspans.
  • These codes provide guidance on design principles, load combinations, material specifications, and other critical aspects of structural design.
  • Designers should be familiar with the specific requirements of each code and apply them appropriately based on the project's location, intended use, and other factors.

Load Combinations and Limit States

  • The structural design should consider various load combinations, including dead loads, live loads, environmental loads (wind, waves, currents), and accidental loads (vessel impact, seismic events).
  • Limit state design principles should be applied, considering both ultimate limit states (ULS) and serviceability limit states (SLS).
  • ULS design ensures that the structure has adequate strength and stability to resist collapse or failure under extreme loading conditions.
  • SLS design ensures that the structure remains functional and serviceable under normal operating conditions, with acceptable levels of deflection, vibration, and other performance criteria.

Articulation and Structural Movements

  • RoRo ramps, linkspans, and walkways are subject to various movements and deformations due to factors such as vehicle loads, ship motions, tidal variations, and thermal effects.
  • The structural design should incorporate appropriate articulation and movement joints to accommodate these deformations without inducing excessive stresses or compromising the overall stability of the structure.
  • Articulation points may include pivot bearings, sliding bearings, or flexible connections, depending on the specific requirements of the project.
  • The design should also consider the potential for differential settlement between the shore-based structure and the supporting foundations, providing suitable adjustability or tolerance to maintain a smooth and safe transition.

Future Trends and Developments

As the maritime industry continues to evolve, RoRo ramps, linkspans, and walkways will need to adapt to new technologies, environmental concerns, and operational requirements. This section explores some of the key trends and developments that are likely to shape the future of these critical infrastructure components.

Automation and Smart Technologies in RoRo Operations

  • The increasing adoption of automation and smart technologies in the maritime sector is expected to have a significant impact on RoRo operations, including the design and operation of ramps, linkspans, and walkways.
  • Automated mooring systems, which use sensors and actuators to control the mooring process, can help to reduce the time and labor required for vessel berthing, while also improving safety and reliability.
  • Smart monitoring systems, using sensors and data analytics, can provide real-time information on the performance and condition of RoRo infrastructure, enabling predictive maintenance and reducing downtime.
  • Autonomous vehicles and cargo handling equipment may also influence the design of RoRo ramps and linkspans, requiring new safety features, traffic control systems, and communication protocols.

Sustainability and Environmental Considerations

  • As environmental concerns continue to grow, the design and operation of RoRo ramps, linkspans, and walkways will need to incorporate sustainable practices and technologies.
  • The use of environmentally friendly materials, such as recycled steel, low-carbon concrete, and sustainable timber, can help to reduce the carbon footprint of these structures.
  • Energy-efficient lighting, heating, and ventilation systems can also be integrated into the design, reducing operational costs and environmental impacts.
  • The adoption of electric or hybrid-powered cargo handling equipment and vehicles can further reduce emissions and noise pollution associated with RoRo operations.

Modular and Adaptable RoRo Ramp and Linkspan Designs

  • The development of modular and adaptable RoRo ramp and linkspan designs is another key trend that is expected to gain momentum in the coming years.
  • Modular designs allow for the rapid assembly and disassembly of infrastructure components, enabling ports to quickly respond to changing operational requirements or market conditions.
  • Adaptable designs, which can accommodate a wider range of vessel sizes and types, can help to future-proof RoRo facilities and reduce the need for costly retrofits or replacements.
  • The use of standardized components and interfaces can also facilitate the interchangeability of equipment and systems, improving operational flexibility and reducing maintenance costs.

Conclusion

RoRo ramps, linkspans, and walkways are essential components of marine transportation infrastructure, playing a crucial role in facilitating the safe and efficient movement of vehicles and passengers between ships and shore. As the demands on global shipping continue to grow, the design and operation of these structures will become increasingly important in ensuring the reliability, sustainability, and competitiveness of the maritime industry.

In my experience, the most crucial aspect is in determining the vertical geometry required that gives minimal downtime. The best way to achieve this is to get accurate detials of the design vessels and their ramp geometry – as this is usually fixed.

Once you have this, you are noramlly limited to space behind the quay wall cope line and also cope line elevation – from here it is about putting these together to see how good / bad the downtime might be and getting taht agreed with all stakeholders.

Here are some great resources I reccomend to get a better understanding:

Resources for Learning More About Marine Structure Design

For those interested in further exploring the fascinating world of marine structure design, there are many excellent resources available. Here are a few recommendations to get you started:

  1. "Port Designer's Handbook" by Carl A. Thoresen – This comprehensive guide covers the planning, design, and construction of port and marine structures, including RoRo ramps and linkspans.
  2. "British Standards Institution (BSI) – BS 6349 Maritime Works" – This series of standards provides detailed guidance on the design, construction, and maintenance of maritime structures, including specific recommendations for RoRo infrastructure.
  3. "PIANC (World Association for Waterborne Transport Infrastructure)" – PIANC publishes a wide range of technical reports and guidelines on port and waterway design, including specific guidance on RoRo facilities and operations.
  4. "CIRIA (Construction Industry Research and Information Association)" – CIRIA offers a variety of publications and training courses on maritime engineering and construction, including guidance on the design and maintenance of RoRo ramps and linkspans.
  5. "International Association of Classification Societies (IACS)" – IACS and its member societies, such as Lloyd's Register, provide rules and guidelines for the design and construction of ships and marine structures, including RoRo vessels and infrastructure.
Adam

I am on a journey to embracing a less stressful, more self sufficient life through my passions for renewable energy, off grid living and financial independence.

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