# Aluminium Beam - is it fit for purpose? Can it easily support this load? [closed]

I want to mount two patio heaters on my terrace in front of a window wall. I cannot attach anything directly to the window wall so I am going to run an aluminium box beam between two brick columns. The beam will be 5000mm long. The beam dimensions are 80mm x 40mm with a 4mm thick wall, 13kg in weight. The heaters weigh 6.5kg each and are 1000mm long. They will be 1000mm from each end and therefore 1000 from each other. I need to drill 8 x 8mm holes for mounting brackets (2 brackets per heater, 2 holes per bracket).

I am sure the beam will deflect a little - any serious risk of collapse?

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– Wasabi
Commented Mar 20, 2017 at 11:09
• This is either a homework problem or something for which you should consult a structural engineer Commented Mar 20, 2017 at 12:52
• The weight of the heaters is just a rounding error, compared with what happens when somebody decides to sit on the middle of the beam - or stand on it to clean the windows! Commented Mar 20, 2017 at 16:05
• What is the maximum allowable bending stress of the aluminum you have? Commented Mar 21, 2017 at 13:08
• Commented Mar 21, 2017 at 13:36

Using the 5th equation from the bottom the displacement is:

disp = Wa^3b^3/3EIL^3

For all the loads W = 33N

for the first and fourth a = 1 and b = 4 for the second and third a = 2 and b = 3

E = 69 x 10^9 (Elastic Modulus of Aluminium)

I = 7.11x10^-7 (Second moment of Area)

Ends up being:

disp = 0.001m

So at the middle x = 2.5

So displacement = 0.0025m

Sounds like it should be fine.