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Newbie

## Beam Deflection Problem

Hi all,

I am an engineering student stumped on a beam deflection problem. I have been working on this problem for a bit of time trying to find a plot of deflection vs position and having some difficulty. The shear and bending moment diagrams look right to me, however the deflection shows a positive deflection at the right support, where I believe it should be zero. Any help is appreciated, thank you.
10 REPLIES 10
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## Beam Deflection Problem

The way in which a beam is supported affects the way the beam bends. Mathematically, the method by which a beam is supported determines the boundary conditions for the differential equation that models the deflection of the beam.

So, you didn't consider the boundary conditions.

For a simply-supported beam, you must use the following boundary conditions:

y(0)=0; Because the beam is pinned to its support, the beam cannot experience deflection at the left-hand support.

y(L)=0; The beam is also pinned at the right-hand support.

y''(0)=0; As for the cantilevered beam, this boundary condition says that the beam is free to rotate and does not experience any torque. In real life, there is usually a small torque due to friction between the beam and its pin, but if the pin is well-greased, this torque may be ignored.

y''(L)=0; In the same way, the beam does not experience and bending moments on its right-hand attachment.

See an example in the next link:

http://www.ptc.com/appserver/wcms/standards/fileothumbredirect.jsp?&im_dbkey=59836&icg_dbkey=888

Regards,

Fernando.
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## Beam Deflection Problem

Some of your expressions did not evaluate on my screen. You need to include the constants of integration when you go from the moments through the slopes to the deflexions. Then the constants are determined by use of the boundary conditions.
Have look at the attached, it is a bit simpler than the previous one, only one end cantilvered!
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## Beam Deflection Problem

the file did not go, try again.
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## Beam Deflection Problem

The file stilldoes not seem to go properly, could it be because it contains an EXCEL table?
Here it is again in an earlier form, with Mcad data tables.
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## Re: Beam Deflection Problem

http://www.ptc.com/appserver/wcms/standards/fileothumbredirect.jsp?&im_dbkey=59836&icg_dbkey=888

but the document does not exist any more.  do you have another link that have an similar beam deflection example.

thanks, gideon

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## Re: Beam Deflection Problem

DEAR FERNANDO,

PLEASE KINDLY GIVE ME MORE LINKS AT PTC SHOWING PEOPLE HOW TO SET UP BOUNDARY CONDITIONS TO DETERMINE THE DEFLECTIONS OF BEAMS.

THANKS, GIDEON

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## Re: Beam Deflection Problem

Hi Gideon,

1. There's no need to shout, forum members understand lowercase just as well.

2. Dit you notice that all posts before your first one are some 12 years old?

3. Over the past 12 years the forum information has undergone two major and a couple of minor migrations. Due to that, a lot of information, especially attachments, got lost.

Success!
Luc

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## Re: Beam Deflection Problem

sorry for offending you using uppercase before.

thanks for the info

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## Re: Beam Deflection Problem

Please post your current attempt.  Beam deflection problems come in all sizes and shspes.

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## Re: Beam Deflection Problem

thanks, i found the solutions somewhere else
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