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Beam held up by two columns 
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#1
Aug914, 10:44 PM

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Beam held up by two columns
I apologize in advance if you think this should really go in the homework help area, I am not sure because this isn't a homework problem, but rather my struggle to understand and carry out concepts. If it needs to be reposted, or moved, I understand. :) In a building a beam is held up by two columns, and only two columns. I need to show that the columns are strong enough to hold up the beam. I thought the best way to do this would be to find the safety factor, and by showing that this value was high enough I would know that it would work. Safety factor can by shown by, Ultimate load/actual load Or, Design load/ expected load I know the Tensile yield strength is 345 MPa (50 ksi) and tensile ultimate strength 450 MPa (65 ksi) of the column. The cross sectional area of the column I found to be, 8.109 in^2, which is also 0.20596 meters. It is an I beam that I calculated the cross sectional area for. How do I find out the force that the two columns can hold? That way I can use the safety factor with the load method. Or is that the wrong way to do it? Keep in mind, I am trying to find the safety factor, so I can't assume its anything to help me find other data. 


#2
Aug1014, 01:10 AM

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You want something like this?
http://www.efunda.com/formulae/solid...tical_load.cfm 


#3
Aug1014, 05:14 PM

P: 15

That looks very helpful but I am not sure, that website incorporates column buckling which I wasn't going to include as a factor. Then again, column buckling could be a major factor in this situation.
What is really hinges on then is, would it be possible for a column to not be strong enough to hold the beam but not buckle in the true sense? Or perhaps I don't understand the concept of column buckling. 


#4
Aug1014, 06:42 PM

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Beam held up by two columns
The thing to realize about buckling, it is a phenomenon which is related to the stability of the column under load. Long, skinny columns can buckle with relatively little load applied to them, while short, squat columns will not exhibit any instability until the material starts to fail for other reasons. This article illustrates some of the key concepts to learn about how to analyze buckling in columns: http://www.ahengr.com/som/10_buckling/text_101.htm 


#5
Aug1014, 07:00 PM

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How does the situation change when there are two columns instead of just one?
Should I try and see if the columns will hold up outside of the buckling situation? 


#6
Aug1014, 07:20 PM

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derail, It may be useful to discover how others have already dealt with and solved your issues. We may, with some humility, look backwards to the Romans two thousand years ago, keeping in mind the huge influence Roman archeticture has had on today's. See, for example:
http://www.ancient.eu/Roman_Architecture/ http://en.wikipedia.org/wiki/List_of...ictory_columns http://www.oneonta.edu/faculty/farbe...hitecture.html Cheers, Bobbywhy 


#7
Aug1014, 07:45 PM

P: 15

I am not designing columns from scratch, these columns are actually I beams. I am just trying to prove that they are strong enough to hold the weight of the beam and roof. So I am trying to find the force they can hold. I thought I could do this with the safety factor.
How does the fact that there are two columns effect the column buckling equation? 


#8
Aug1014, 09:22 PM

P: 15

I am trying the method and equation at http://www.efunda.com/formulae/solid...tical_load.cfm
How do I calculate the Young's Modulus? This requires stress which requires force. What force would be used? 


#9
Aug1014, 10:47 PM

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For steel at room temperature, it is about 30 x 10^{6} psi, or 200 GPa. 


#10
Aug1114, 02:51 AM

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#11
Aug1114, 07:02 AM

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