An empty container yard is a ground problem, not a roof one
An empty container yard stores containers in stacks, moves them with reach stackers or forklifts, and releases them through a gate. Almost all of the engineering is in the ground and in the traffic.
Stack loads are large and they are concentrated
An empty container is light for its size, but seven of them stacked put the corner castings of the bottom one under a load that has to be spread by the pavement.
The load arrives at four points, not over the whole footprint. A pavement designed for an area load will punch through at the corners; the design has to consider the corner loads and the spacing between stacks.
That is why container yards are usually heavy-duty pavements with a defined stack pattern, and why a yard paved to a road standard develops ruts where the stacks sit.
The reach stacker is the other load
A loaded reach stacker is heavy, and its wheel loads are concentrated. It also turns, which applies a horizontal force to the pavement surface.
The turning areas are therefore the part of the yard that deteriorates first, and they are the part where the pavement needs the most attention. A yard designed around the stack pattern but not around the machine will fail at the corners.
The gate is the only real building
Containers enter and leave through a gate where they are identified, checked and recorded. That gate needs a booth with a view of the lane, a canopy over the inspection position, and space for a truck to stop without blocking the next one.
It also needs the IT and the power, which in a remote yard usually means a small plant room and a generator. Those are the buildings the project actually needs to design.
Drainage matters more than in a warehouse
A yard is a large impervious area. Rain that falls on it has to go somewhere, and if the falls are not designed the water collects where the stacks are and the pavement fails from the base up.
In a high-rainfall climate that is the single most common cause of early yard failure, and it is a civil design question rather than a structural one.
Lighting masts are structures
High masts for yard lighting are tall, slender and exposed, and they carry a large wind area at the top. They need their own foundations and their own design, and they are frequently procured separately from everything else on site.
Where the masts also carry cameras or communications, the load case changes and the foundation has to be sized for it from the start.
What I want before drawings
- The stack height and the stack pattern, and the container types handled.
- The handling machine types and their wheel loads.
- The yard pavement specification and its drainage falls.
- The gate layout and the truck queue length.
- Whether lighting masts carry anything beyond luminaires.
- The wind speed for the site in km/h from the applicable local code, not a round number.
Container yard projects are usually judged by how quickly they can start operating, which puts the pavement and the gate at the front of the programme. The steelwork is a small part and should not be allowed to delay them.
Written by Johnny Joe, who advises owners and project managers in Africa and South America on steel buildings. If this decision is live on a project, send the layout and the constraint that worries you and I will tell you what it changes.
Related: traffic layout before the frame · the gate and the queue · container handling limits · clear height set by the stored item
