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Steel angle beam working out the defection

by guuy18
Tags: angle, beam, defection, steel, working
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guuy18
#1
Nov23-10, 01:03 PM
P: 4
1. The problem statement, all variables and given/known data

I have a steel angle (40 x 40 x 5mm) which is welded to box section either side it is 1000mm in lenght. It will have have load of 45kg on it (point load). I need to find the maximum deflection of this beam, which i think will come under a fixed-fixed type beam.

2. Relevant equations

i assume i need the young modulus of this material and the moment of inertia to be able to work this problem.

3. The attempt at a solution
I am lost in where i have to start with this, how do i find the moment of inertia(do i need to find the neatral axis?) and what is the bes method of finding the deflection out .

Any starting point would be useful this is a project for college where i am designing a storage device and this part will be holding a slider for the drawers, however for the drawers to function properly there needs to be minimum deflection. if i am wrong please say, this is all a learning curve for me.
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pongo38
#2
Nov23-10, 02:07 PM
P: 699
You need to draw a dimensioned sketch of the cross-section, so that your question can be correctly understood.
guuy18
#3
Nov23-10, 03:16 PM
P: 4
Click image for larger version

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a = 40mm
b= 40mm
c = 5mm

ignore rads

pongo38
#4
Nov23-10, 03:46 PM
P: 699
Steel angle beam working out the defection

How does this angle cross-section relate to the box section to which it is welded? How big is the box-section? As you haven't provided this information, do you consider that it is irrelevant? And how do you know that the ends of the beam are moment-fixed (if that is what you meant), Can you identify the point of application of the load on the section? When you ask about the deflection, do you mean the longitudinal deflection on a span of 1m or do you mean the deflection of the tip of the angle section relative to its vertical leg; or both?
guuy18
#5
Nov23-10, 04:17 PM
P: 4
The angle section is welded to the box section by a slot being machined out of the steel angle so it can be slotted into the box section

Heres a crude drawing of how its attached to the box section :

Click image for larger version

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The size of the box section is irrelevent but if this info is needed it will be 50 mm X 50mm x 4mm wall section.

I am not sure how to identify if they are moment fixed, what would suggest they are or not.

im after the longitudinal deflection on a span of 1m on the steel angle

The Slider is going to be bolted on the steel angle which is going to take a load of 45 kg distributed evenly along the slider.
pongo38
#6
Nov23-10, 04:56 PM
P: 699
In post #1 you said the load was a point load. In #5 you say it is distributed evenly. My suggestion is that you mke a lower bound estimate of the deflection, assuming a UDL and a fixed-ended beam; and an upper bound estimate assuming pin-ends and a central point load. Then, if these bounds are too far apart, you can do additional work to bring them closer. To get the deflection the easiest way is to find a formula in a book such as steel designers manual or similar. To get the moment of inertia, tables are published by the steel people who make the angle. If you want to do it from first principles, you will first need to find the centroid of the section, and then its second moment of area.
guuy18
#7
Nov23-10, 05:14 PM
P: 4
ok thxs for the quick reply i will do what you suggested and i will post back my finding cheers .

And many thxs for the help.


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