Statics problem - is the mistake mine or the solution manual?

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Femme_physics
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So I got everything right other than Rd (the end). I personally think there's a mistake in the solution manual.

Homework Statement



Basically these are all pin joints, even the "hydrolic cylinder" (CD) is weightless and connected by pin joints, so the fact it's called or drawn as "hydrolic cylinder" doesn't matter.
F = 80 [kN]
Ignore the weight of all the beams

http://img198.imageshack.us/img198/3063/sketch1999.jpg


The Attempt at a Solution



Attached
 
Attachments
  • Handwritten statics solution on graph paper for problem 6 (1999): a truss frame with a 80 kN load at top, dimensions 1, 3, 2, and force equilibrium equations giving Hy = 20 kN, Ay = 60 kN, Hx = 20 kN, Ex = 20 kN, Ey = 20 kN, and resultant RH = 28.284 kN.
    991.jpg
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  • Handwritten statics solution on grid paper: sum of Fx = 0 gives Ax = 20 kN, RA = sqrt(Ax^2 + Ay^2) = 63.245 kN; sum of MD = 0 gives By = 20 kN; sum of Fy = 0 gives Dy = 80 kN; sum of MC = 0 gives Dx = 80 kN; RD = sqrt(Dx^2 + Dy^2) = 113.137 kN, with free-body sketches of beams BE and DC.
    992.jpg
    18.4 KB · Views: 448
Last edited by a moderator:
I can't fault your solution.
I give it my stamp of approval. :)

What's the answer of the solution manual?
 
w00t! Another mistake to add to my blog :)

Thanks for the stamp!

Answer manual's Rd = 226.27 [kN]

Solution manual full solution attached
 
Attachments
  • Handwritten solution to a truss statics problem showing the structure with force F = 80kN, labelled joints A to H, dimensions a and 2a, and the reaction equations and final results FH = 28.28kN, FA = 63.25kN, FD = 226.27kN.
    solman.jpg
    22.2 KB · Views: 500
Femme_physics said:
w00t! Another mistake to add to my blog :)

Thanks for the stamp!

Answer manual's Rd = 226.27 [kN]

Solution manual full solution attached

Yes, there's indeed a mistake in the solution manual.
They took the force at E in the wrong direction.
They really should have drawn proper free body diagrams as you did! :)
 
*pats self on shoulder*

Thank you Serena! :)
 
i also believe your work is correct. and it is very clear and easy to follow; nice job.

cheers