The Engineering Bid

Perhaps the most important aspect of building with containers are the modifications of the boxes themselves. I assume that if your reading this blog that you are already familiar with the characteristics of conex boxes. Forty foot hi-cube conex boxes are capacity rated to carry over 80,000 lbs. They stack full containers aboard ship at least five high, so they have both solid floors and virtually crush proof corners. Both sides and top are really just curtain walls, however, they provide enough shear wall strength to keep the whole from racking and the floor from sagging.
Every engineer that I've spoken to about using containers always refers to them as box girders. Their calculations concerning the removal of sections of the curtain wall, whole lengths of wall as well as windows and doorways, come down to proving that modifications do not violate the integrity of the box girder.
This is a section drawing of an interior container wall in one of the pylons of the house on Bethel Island. Where the curtain wall was removed a steel square tube 2x4" header on 2x2" square tube posts re-supports all the loads. These were the engineered modifications used on the Portland project when joining two containers side by side with open walls. Since we are modifying standardized structures we can design using standard pre-engineered modifications. The steel 2x5 1/2 square tube at the bottom of the container has yet to be engineered. It has welded clips attached to receive glue laminate beams that will carry the center span between the container pylons. They are supported underneath by 4x4" steel posts to carry the point loads down to the foundation.

Our preliminary report from the soils engineers is that their foundation recommendation will be for the use of grade beams set on driven piles. When I have built previously with containers the foundations consisted of grade beams that spanned only the ends of the containers but included footings to support the point load of the posts. I expect that will be how the structural engineer will handle this project. I have never worked with driven piles before so it's inappropriate for me to present a foundation sketch. As you can see these sketches could easily have been done on cocktail napkins. I've hired a real draftsman to put this idea across to the engineers that are about to receive my Request For Proposal.

I've collected other appropriate modifications, such as welding the corners together and how to design embed points in the foundation footings to weld a project to the ground. These will come in handy, too. The better you can explain what you want to do to an engineer the more helpful and efficient they are going to be. You are going to want to make sure that they are looking at the type of containers you are building with. I once hired an engineer that used as his model containers that did not have a square tube top rail. The modification that he designed used custom steel headers that would have cost five times as much as off the shelf steel. I ended up paying for the redesign, it was not cheap either.