Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Finding the allowable uniform load

  1. Dec 14, 2009 #1
    1. Determine the allowable uniform load w if the allowable bending stress is 24ksi and
    Given: I=12,800in^4; c=16.965in

    2. I know that Mmax=[tex]\sigma[/tex]max/c(I); And Mmax=wL[tex]^{2}[/tex]/8

    3. I solved for Mmax=18,107.869 k in; but I dont understand how to solve for w with the two P forces also. If somone could help me with this part I would greatly appreciate it. Thanks

    Attached Files:

  2. jcsd
  3. Dec 14, 2009 #2
    some of the moment capacity is used up by the moment of 3P in the central portion of the beam, thus leaving less available for the uniform load. I suggest you first draw the M diagram for the whole beam.
  4. Dec 14, 2009 #3
    Thats supposed to be a 3ft from P to the edge, sorry my drawing skills are not great. I already did the M diagram that is where i came up the max of 575. I just dont know how to solve for the w.
  5. Dec 15, 2009 #4
    Maybe you are missing the point that p=15w. Therefore M isn't just wL2/8 but also 36x15w=540w k.in at the centre
  6. Dec 15, 2009 #5
    O ok, so M would be equal to wL2/8+540w?
  7. Dec 15, 2009 #6
    Yes, but be careful to use consistent units throughout. Like kip inches, or whatever.
  8. Dec 15, 2009 #7
    ok thanks for the help
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook