strength of steel angle vs rectangle tubing

huangyhg

strength of steel angle vs rectangle tubing
can anyone give me a hand with this? my background is eletronics not structural. trying to find out the strength of 2x1 1/2 3/16 wall tube vs 2x2 or 2x3 steel angle for extending a trailer platform. my concern is understanding the loads the existing platform can handle.
thanks
rich
there are several differences and they are too numerous to list. it all really depends on how they will be used and loaded. it all starts with few fundamental facts:
1. steel angles are (unless specified) are rolled from astm a36 steel (yield strength of 36,000 psi).
2. most tubes min. yield strength of 46,000 psi
3. the angle is an open section. when it is loaded it creates unsymmetrical loading conditions (bending).
4. angles are not suited for torsional loading.
5. tubes are excellent for torsional loading because they are closed section.
of course without seeing the framing of the platform and how it is loaded, it would be difficult to comment.
good luck
the platform is 6'wide and 8'long supported in the center and made of 2x1 1/2 rectangle tube 3/16 thich
i wanted to extend it 1 foot  each length to 10 ' long . was going to use the  rect tubing for the extensions but didn't know the load capabities. where could i get the formula to understand the max load capable for the tubing at different end loads?
appreciate the help!
rich
rich,
i have several questions:
1. how is it supported and in how many locations? this is important.
2. what is the load that you anticipate?
3. is the extension going to be cantilever? this is critical for the new splice joint detail. if the joint is to carry moment, then it must be a moment connection.
4. are there any filler beams/elements in his platform?
5. if the answer to 4 is yes, how far part are they? how are they connected to the perpendicular   
thanks for the replies!
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this is the layout of the platform, 6' wide 8 ' long suported across the center of the 8' length. both end rails and perpendicular braces are 2x1 1/2 rectangle steel 3/16" thick (2" in the vertical plane). i'd like to know what the maximum end loads are for this layout is.  would like to have 1400lbs dead load at each end of the cantilever(8' apart)it is a trailer so one end would be a supported end though.
thanks for the help!