Phone
(678) 225-4900STRUCTURAL CONSIDERATIONS FOR ARCHITECTS
I’ve worked with a number of architects on shipping container projects, most recently a group of students attempting to design low income housing in Atlanta. Unfortunately, many of the designs I’ve seen are horribly difficult to structurally design, and extremely difficult to build. The whole idea of building with shipping containers is ease of construction, low cost, and recycling (green building). This idea is hard to accomplish if you design like gravity doesn’t exist. So, in the interest in being helpful in the concept stage, I am putting out some important tips here:
1. Respect the Container: In one project that I worked with that appears to have died (too expensive to build), the architect wanted to slice the container in half, the cut line being halfway up the side. Try to imagine just how hard this would be, to try to cut a huge steel box in a straight line into two halves in any direction. As usual in such situations, the architect would not believe me that this was not practical. He went ahead with his design, the project costs got too high, and the building will probably never get built. Slicing the container in different ways is not reasonable, leave it alone.
2. Preserve the Corner Posts, Top, and Bottom Rails: When we start cutting into these members, it makes it very difficult to work with the container. They need to be left alone so that we can work within the structure as we need to in order to reinforce it.
3. Cantilevers Are Difficult And Expensive. For a number of reasons, there always is a desire to cantilever a container, one on top of another. The problem is we are no longer carrying the load through the connectors that have been built into the containers. So, on the rear of the cantilever, a column has to be added into the container side, and where the cantilever sets over the edge of the container I have to reinforce the bottom rail. See the drawing for more information. While architecturally it is probably desirable to break up the face of the building, please be aware it will add to the cost.
In the photos below, you can see that beams were placed under the bottom of the containers on the left to add support - that is probably because of the cantilever. This is the shipping container house in Redondo Beach, which we did not design (the architect was De Maria Design Associates).
4. Stack The Containers Right Side Up: For some reason, there is a desire to place the containers upside down, sideways, on end… I’m sure this looks great architecturally, but we’re starting to run the cost way up there. Again, Respect the Container, stack it the way it was built. If you need to do this for some reason, go ahead, but the cost for engineering will be high, and so will construction.
5. When You Remove the Sides, the Container Looses Strength: If you take the sides off of a container, the bottom rail has very little strength left; it will only span about 10’ on its own. The top rail has basically zero strength, it will sag under its own weight. To counter this, we have to do a number of things to reinforce the bottom and top rails. It’s not a big issue, but in some cases it may be necessary to place beams under the bottom rails, since there is very little room for reinforcement on the sides of these rails when you place containers side to side.
6. Stack Containers Along the Same Axis: When you stack containers at angles to one another it causes all sorts of torsional problems in wind loads, and makes connecting them very difficult. If you stack the containers at right angles, it causes problems too, because again, connecting them gets difficult.
Note how in this house they had to add beams on top of the container at ground level, and it looks like they built a structural frame around the top container so it would cantilever OK. You can see columns were added in the top and bottom containers at the connection point to add strength. This is an interesting idea as a concept/experiment, but is a lot of structural modification for about 500 SF of building.
As with any kind of structure, you can build whatever you want, however the more complex it is, the more it will cost. Since we are trying to cut our costs with shipping containers, we should not be treating them as a veneer, but take advantage of their inherently strong structure.