A36 Angle Iron Beam 1

[RachaelSelby]

I think I am having a serious brain lapse.

I need to calculate the maximum load capacity of an A36 6x4x3/8" anngle iron beam with a length of 20 ft.

For the life of me, I can not even think of how to begin this calculation.

Can anyone get me started? Thanks!!

 

[Spike6901]

Can you be more specific? Are you talking about tensile, deflection, compressive, etc?

 

[StephenEd]

Single-angle flexural members are very touchy and complex. They make my brain hurt too.

Methinks a 6x4 spanning 20' won't work, regardless of the loading!

 

[Taro]

One way (the hard way) is to use the specification for single-angle members that is included in the AISC steel manual. The easy way is to use the tables in the paper "Safe Load for Laterally Unsupported Angles" by Leigh, Thomas, and Lay in the AISC Engineering Journal, 1st quarter 1984. You can download the article from

http://www.aisc.org

(free for AISC members).

 

[desertfox]

Hi RachaelSelby

How are you loading this beam ie:- single point load, uniformly distributed load, several point loads or combination of both. Secondly is the beam simply supported
or built in as this will make a difference to the formula
you need to use.
I will assume for the moment that it is a simply supported
beam with a central point load.

therefore stress = M*y/I

where M= bending moment

y= distance from beam surface to the neutral axis

I= second moment of area of the angle.

a word of caution here if the load applied does not go through the centroid of the angle then there will be twisting of the beam. Also the second moment of area will be different depending on which of the legs is horizontal or vertical.
So to calculate the maximum point load the beam can take at the centre you need get your design stress into the above formula and transpose to find M the bending moment :-

M=stress*I/y now calculate M from the stress and I and y

now M = W*L/2

where W=max point load at beam centre

so once you have the max bending moment M you divide it by the length of the beam and multiply by 2 and this will give you W.

regards

desertfox