Structural specifications for 20'-0" shipping containers

[PEFLWI]

I am looking for structural details or drawings for 20'-0" shipping containers. I need to understand the structural elements because my clients containers are bulging when stacked only 2 high. The shipping people are requiring a concrete pad to store the containers, but they have not provided an engineering analysis that proves this is the problem.

 

[Ceinostuv]

thread559-406734

See the thread above, the original link to the ISBU Association is a dead end but my understanding is that the website still hosts the drawings somewhere; I believe it is a one-time fee to purchase the drawings. Full disclosure - I have never used this site because I work with some client-obtained CADs from elsewhere, so I'm not sure what you'll be getting.

Out of curiosity, what elements are bulging? If these are unmodified, ISO containers, the 1C and 1CC should have at least a capacity of about 52 kips per container (newer containers have higher capacities) and the stacking elements (end frames, corner fittings, etc.) are supposed to be tested for up to 760 kips. Based on these values, you should have no issues stacking several units... to hear that a 2-stack is experiencing bulging is surprising.

Judgement-In-Training

 

[dhengr]

Ceinostuv:
Isn’t it true that if they are supporting those containers anyplace other than the corners/end frames or possible at the location of the forklift slots, they might have side buckling problems? The sides are really not designed for significant concentrated vert. loading. Particularly when they start stacking them, and concentrate the weight of several containers. The request for a conc. slab, is a flat surface where you know the primary bearing can/will be at the corners/end frames unless the container is deformed. Do you mean tested to 760k or 76k, and I assume that’s to failure? I don’t have that spec./std., and don’t know the answer, but 760k sounds kinda high.

 

[Ceinostuv]

dhengr (Structural)11 Mar 19 21:23
Ceinostuv:
Isn’t it true that if they are supporting those containers anyplace other than the corners/end frames or possible at the location of the forklift slots, they might have side buckling problems? The sides are really not designed for significant concentrated vert. loading. Particularly when they start stacking them, and concentrate the weight of several containers. The request for a conc. slab, is a flat surface where you know the primary bearing can/will be at the corners/end frames unless the container is deformed. Do you mean tested to 760k or 76k, and I assume that’s to failure? I don’t have that spec./std., and don’t know the answer, but 760k sounds kinda high.

Yes, you are absolutely right and I should have been clearer; I assumed that these were typical, unmodified containers stacked with their corners aligned. Once you start moving the loads away from the corner posts you can start running into issues and I agree with dhengr, the side panels (and top rail too) are not designed for significant vertical loading.

The testing information can be found in ISO 1496, I think an older version of the document is easily accessible online. I meant 760k - the entire assembly is tested to support 760 kips during testing to replicate a 9-high stack of containers. The acceptance criteria is that "the container shall show neither permanent deformation... nor abnormality which will render it unsuitable for use..." so these aren't failure-level loads.

Judgement-In-Training