# Forces on an L - Bracket

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1. Jul 5, 2017

### GBE111

I am installing an L-shaped bracket into a brickwork chimney to support some large pipework. I am trying to work out the forces in each fixing to ensure that I wont be pulling the bracket off the wall once the pipes are filled with water.

I've tried drawing the free body diagram and to resolve the forces and the moments, but I'm not sure exactly how to do it. I've marked the location of where I believe the pivot point to be as X and the two fixings as A and B. Can someone please explain to me how to do this as it is a long time since I did my engineering degree!

P.S the force the fixing can withstand vertically in shear is different to the tensile force. I think this is relevant?

Many thanks,

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2. Jul 5, 2017

### BvU

Hello GBE,
You have the right suspicion there: your $\sum M = F_y L$ seems only part of the story to me (this would be around an axis located on the wall; since the bottom point can't move to the left, let's take that as the preliminary potential axis of rotation)

The condition for 'no pulling offf the wall' would be $\sum M = 0$ and the counteracting torque comes from the wall pulling on plugs A (mainly) and B.

Safest calculation would ignore B (e.g. because the bracket starts to bend there, so the axis of rotation moves up to, worst case, B) and then A needs to resist pulling force $$F_y L\over y-x$$
Make sense ?