A gangway is a walkway from one place to another. They typically consist of a walkway, enclosed or open, from the ground to a vehicle like a boat or an aircraft. This guide describes gangways that provide access to ships, boats, train cars, and truck trailers.
Simpler gangways, like those at marinas, are fixed in length and are installed with one end fixed and the other end free to slide on rollers to compensate for changes in height due to different vessel heights or water level. They are usually flat ramps, but some may have stairs. No-slip surfaces and handrails may be employed to prevent falls. More complicated ones will have power extenders and levelers that are usually fluid powered. These tend to be fixed in ground because of their weight and need for power.
The most important specification is the length to be bridged. Then the vertical height limits are next, since most of the time there is going to be differences in height. The width of the passageway usually start out at three feet wide, then increases up to four. Finally there is the load limit of the structure.
The most common material is steel, usually galvanized or painted. Often aluminum is used, especially in marine and aeronautical applications where weight and corrosion are issues. The walking surfaces are usually treated with various non-metallic coatings for traction such as specialty plastics or even wood. Or in the case of steel, they are grated with small teeth to provide maximum traction.
The most basic gangways are solid inclined ramps, usually with handrails and no-slip surfaces for safety, These can be found at the water front, where they connect floating objects to land. In the picture below, the dock is a floating type, held in position by sliding up and down on vertical poles. The gangway ramp is attached to and extends down from the shore. The lower end is on heavy-duty casters and can slide back and forth along the dock. This is a tidal area so the dock is always at a constant height for easy access to the boats, but the depth of the river varies with the tide and water flow.
Many industrial-use gangways have telescoping power extenders, usually using fluid cylinder power, so its length can be varied to match the vehicle. This way the operator can easily extend, retract, raise, and lower the gangway to match up tightly against the vehicle it is trying to connect to. These are common in harbor and railway settings and are significantly more expensive than simple fixed types due to the need for hydraulic controllers and pumps.
The last type consists of engineered structures that are basically small bridges permanently mounted to the ground on reinforced concrete footings. They are often found in rail yards to provide access to the tops of the rail cars, usually tank cars. They can include power extenders to let the workmen walk safely to the tops of the cars. Some of these types also act as small elevators to lift the operator straight up to the top of the desired car. These are the most expensive and must be custom designed and installed for each application.