I'm not an engineer or anything, but you might be able to use this calculator to get a rough estimate of what kind of loads your structure can hold:
http://www.atc-mechanical.com/calculators/tube-size-using-structural-properties/624
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I'm not an engineer or anything, but you might be able to use this calculator to get a rough estimate of what kind of loads your structure can hold:
http://www.atc-mechanical.com/calculators/tube-size-using-structural-properties/624