Beam Deflection

[itenjc]

I am new to usiing Roark's Formulas for Stress and Strain and need some help. I have a copy of the 7th edition. My question is how do use the table 8.1, 2e (simply support beam with uniform distributed load across beam) to find the deflection at any point x along the beam? Thanks

 

[prex]

Go to the first site below, under Beams -> Simple bending -> Simply supported -> Unif.load : hope it will be easier to use.

prex

http://www.xcalcs.com

: Online engineering calculations

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads

 

[msquared48]

I am looking at the same info in the fifth edition... Better be careful here - this table is addressing axial and bending stresses combined. Read the application on page 147 and 152 with following examples. Do you have that, or just simple bending due to a uniform, or uniformly varying load? Also, note the link back to table 3 on page 100, situation 2e.

Mike McCann
McCann Engineering

 

[itenjc]

msquared48, I just have simple blend if a uniform distributed load accross the entire beam. The beam is L = 15 and I am interested in x = 10.

Thanks

 

[rb1957]

i don't think roark includes generalised deflection data, only the maximum deflection. get out a piece of paper and solve it from 1st principles ... M(x) ... integrate for v(x), integrate for d(x) ... solve integration constants from boundary conditions ... it ain't rocket science !

 

[JStephen]

Back at the first of the table are the general equations for deflections, and then in the particular load case, it gives you specific factors for those equations. Quite a few of the tables are presented in this way

 

[spats]

If I understand you correctly, who needs Roark!

The AISC Manual of Steel Construction gives beam diagrams and formulas under the "Beam" tab. For a simple beam with uniformly distributed load the formula for deflection is

Delta(x)= (wx/24EI)(l^3-2lx^2+x^3)

where "x"=distance along the beam, "w" is the load/ft, and "l" is the beam length.

 

[JStephen]

True, but it gets much handier for other cases.

 

[abusementpark]

Who the heck is Roark?

 

[hokie66]

He was the original author of this reference, in 1938. So I suppose he is no longer with us, but others have picked up his work and kept it current.

Anybody have a biographical reference?

 

[JStephen]

Not too much online. A couple of other books of which he was author or co-author pop up. And from

http://www.findagrave.com,

the following:
Raymond J. Roark
Born Jul. 25, 1890, Greenville, Kentucky
Died Jun. 1, 1966, Madison, Wisconsin, USA
Professor of Engineering,University of Wisconsin
Son of Mary (Creagon) Roark.
Husband of Margaret M. (Mott) Roark.
Buried in Forest Hill Cemetery, Madison, Wisconsin