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Author Topic: Math Formula Needed  (Read 5399 times)

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CAB

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Math Formula Needed
« on: November 04, 2008, 04:38:12 PM »
This is a engineering problem but thought it would get more views here.

I'm trying to find the formula to solve for the Rod Load in this example.
Anyone have an equation for this?
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jnieman

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Re: Math Formula Needed
« Reply #1 on: November 04, 2008, 04:48:11 PM »
What's the rod spacing and length of canopy?
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Strucmad

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Re: Math Formula Needed
« Reply #2 on: November 04, 2008, 04:49:05 PM »
P = 500/sin(tan-1(2'11.5 / 4'6.5))

This will find you the load, not the stress (ultimate or allowable)..

The 500# is the tributary load right ? (imperial ??)
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Atook

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Re: Math Formula Needed
« Reply #3 on: November 04, 2008, 04:56:23 PM »
The way I calc it:

T=1.83218*W

Where T=rod tension, W=Tributary Load

@W=500, T=916.1
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Strucmad

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Re: Math Formula Needed
« Reply #4 on: November 04, 2008, 05:05:24 PM »
Quote from: Atook on November 04, 2008, 04:56:23 PM
The way I calc it:

T=1.83218*W

Where T=rod tension, W=Tributary Load

@W=500, T=916.1

Yours is simpler...but we get the same answer :kewl:...... :lmao:
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mjfarrell

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Re: Math Formula Needed
« Reply #5 on: November 04, 2008, 05:07:21 PM »
did he say rod load?   :roll:
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Michael Farrell
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CAB

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Re: Math Formula Needed
« Reply #6 on: November 04, 2008, 05:10:07 PM »
Thanks so much for the replies.

Imperial, Yes
500 pounds tributary load, Yes

I would think you needed to consider the angle of the rod.
Thanks PS_port

Atook is the 1.83218 constant for a specific angle?

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CAB

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Re: Math Formula Needed
« Reply #7 on: November 04, 2008, 05:11:39 PM »
PS_Port is there a difference in this situation for the Load & Stress?
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Maverick®

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Re: Math Formula Needed
« Reply #8 on: November 04, 2008, 05:13:49 PM »
I saw that CAB.  :wink: :-D
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Greg B

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Re: Math Formula Needed
« Reply #9 on: November 04, 2008, 05:14:25 PM »
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Strucmad

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Re: Math Formula Needed
« Reply #10 on: November 04, 2008, 05:14:38 PM »
Yes CAB that is for that angle...

1/sin(tan-1(2'11.5 / 4'6.5)) = 1.83218


(tan-1(2'11.5 / 4'6.5)) = your angle



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CAB

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Re: Math Formula Needed
« Reply #11 on: November 04, 2008, 05:25:07 PM »
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CAB

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Re: Math Formula Needed
« Reply #12 on: November 04, 2008, 05:26:33 PM »
Quote from: PS_Port on November 04, 2008, 05:14:38 PM
Yes CAB that is for that angle...

1/sin(tan-1(2'11.5 / 4'6.5)) = 1.83218


(tan-1(2'11.5 / 4'6.5)) = your angle

Thanks for the clarification.
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Atook

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Re: Math Formula Needed
« Reply #13 on: November 04, 2008, 05:26:45 PM »
Stress will be the tension in lbs divided by the cross sectional area of the rod.

And Port is right, my solution was for the drawing shown. Port's solution can be used for other triangles, just substitute your H & W values.

My solution stayed away from trig (sort of) and is:

 T=W*L/H

Where T=tension in lbs, W= load, L=length of hypotenuse, and H=height.
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Strucmad

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Re: Math Formula Needed
« Reply #14 on: November 04, 2008, 05:28:19 PM »
CAB,
Load is just the load being applied to the rod, the diameter of the rod can vary,

The load will remain the same but the stress developed in the rod will be dependant on the diameter,

stress = load / area of steel.

This is where imperial start to loose me. (here Newtons / millimetres 2 = MPa)
I believe you guys work in KIPs ' (Pounds per square inch) so as long as you keep your units the same you should be ok.

Might have to wait for Bob G. to check..? :oops:
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