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Which frame will be better to hold the weight?(50x50 c-profile) My boss claims 45 degree is always desirable, but in this circumstance it looks like the lower angle is better.

enter image description here

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  • $\begingroup$ it looks like the lower angle is better ... how did you reach this conclusion? $\endgroup$
    – jsotola
    Commented Jun 4 at 19:05
  • $\begingroup$ why are you asking? $\endgroup$ Commented Jun 4 at 20:28
  • $\begingroup$ to determine if you attempted to answer the question yourself $\endgroup$
    – jsotola
    Commented Jun 4 at 21:20
  • $\begingroup$ "Better" is not a specification. If you do the math you'll see that the compression of the support changes with angle, as does the bending of the horizontal member. Not knowing the loads or dimensions of the system, you might not need a support at all. $\endgroup$
    – Tiger Guy
    Commented Jun 4 at 21:59
  • $\begingroup$ @TigerGuy It supports a cable tray so its hard to specify the load. currently the load bends the c-profile down 5 cm. $\endgroup$ Commented Jun 5 at 6:11

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For a rough estimate let’s say the weight of the frame members are negligible compared to the load.

Let’s call load P at the center of the brown tray in your diagram at a distance L from the top left support on the wall and the vertical distance between the bracket’s support at wall H.

If we assume the bracket is rigid there are some constant reactions that are independent of angle of the brace.

Those are the shear at bolts or screws connecting the bracket to the wall ant tension force on top bolt and compression force on the bottom. $$ \Sigma M=0. \ \ PL-TH =0 \ , \ T=C=PL/H $$ $$ V_{ top} = V_{bot} =P/2$$

And compression on the bottom brace is

$$ C_{bot}= PL/H *cos \alpha $$

  • V shear
  • Alph is the angle of the brace from horizon.

In these applications because the loading is not extreme it is acceptable to make the angle more than 45 degrees to keep the space under bracket more open.

However one must watch the bending moment on the top member.

If we call the length of top member cantilevered from the corner of the right joint of the bracket in case A, L2, the bending moment will be $$ M=PL2.$$

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