Can this be solved by statics?
Can this be solved by statics?
(OP)
I am tying myself up in knots with this one. I have a system like the picture to assess. There are a variety of geometric configurations so i was planning to plug it all into a spreadsheet, but I am not happy that I am programming it right. So, I modelled one scenario and I cannot mirror the results by hand. Nodes 1-3 is 1.57m, 3-4 is 1.83m and 3-4 vertical is 2m. The rotated roller at 4 represents a slope, so it will provide a restraint but would slip down the slope on its own - member 2 is there to stop this happening.
I can't help feel i'm making a meal of this, but something is wrong somewhere!
I can't help feel i'm making a meal of this, but something is wrong somewhere!






RE: Can this be solved by statics?
RE: Can this be solved by statics?
RE: Can this be solved by statics?
Then summing the forces at Node 3: 2 unknowns (force in Member 1 and the reaction force at Support 3) and 2 equations (sum of Fx = 0 and sum of Fy = 0) lets you solve for the force in Member 1 and the reaction force at Support 3
As I do not know the geometry of your members and supports, I cannot solve it exactly but if I assume that Member 2 and Support 4 are both angled at 45 degrees, i get a force of 11.12 at Node 1 which is only 1.6% different than the value in the image you posted.
Great spirits have always encountered violent opposition from mediocre minds - Albert Einstein
RE: Can this be solved by statics?
RE: Can this be solved by statics?
at node 3, the reaction is normal to element 1, which is a component of the load in member 2
at node 1, the reaction is the other component of the load in member 2.
i think your solution works.
another day in paradise, or is paradise one day closer ?
RE: Can this be solved by statics?
In my time zone its late so I will go through the responses you all have very kindly given me in the morning and respond.
RE: Can this be solved by statics?
RE: Can this be solved by statics?
RE: Can this be solved by statics?
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Can this be solved by statics?
RE: Can this be solved by statics?
I have drawn out the geometry in the top half. At the bottom, I have started with N4 and immediately get it wrong - I know it wrong because I have a vertical reaction equal to the applied load. This can't be right as then if I have a vertical at N3 I lose equilibrium. Surely my triangle of forces at N4 is wrong but I can't see it any other way as this arrangement gives the applied force as a resultant (if you see what I mean).
I think i'd better go back to school after this one...
RE: Can this be solved by statics?
RE: Can this be solved by statics?
My 'problem' with it is that I think the vertical component of reaction at 4 is 22.24kN as drawn on my sketch which does not match the output and cannot satisfy equilibrium if there is a vertical reaction at N3 - is this where I am fundamentally wrong with something?
RE: Can this be solved by statics?
RE: Can this be solved by statics?
I should add that I am not blindly assuming the computer is right here, and I don't need to get results that match 100%, but I need to be right!
The help offered so far is really appreciated.
RE: Can this be solved by statics?
RE: Can this be solved by statics?
RE: Can this be solved by statics?
another day in paradise, or is paradise one day closer ?
RE: Can this be solved by statics?
another day in paradise, or is paradise one day closer ?
RE: Can this be solved by statics?
And the appreciation for not believing the computer is appreciated!
RE: Can this be solved by statics?
another day in paradise, or is paradise one day closer ?
RE: Can this be solved by statics?
No, because as noted above, assuming rigid supports, the force in the left hand beam is horizontal, so there will be no moment in either beam,
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Can this be solved by statics?
if a moement was applied at node 3, the structure could support it.
so it follows that if the members can support bending, and if the joint at node 3 allows it, then an internal moment would develop at node 3.
another day in paradise, or is paradise one day closer ?
RE: Can this be solved by statics?
RE: Can this be solved by statics?
RE: Can this be solved by statics?
I agree with the calculated force in the sloping member of 16.41 kN, and so does Strand7 (both with a hinge at the bottom, and a moment connection).
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Can this be solved by statics?
RE: Can this be solved by statics?
The conclusions are:
Including the moment at Node 3 makes less than 0.1% difference to the reaction values.
Spreadsheet calculations agree with FEA results (Strand7) almost exactly.
Doing the calculation on a spreadsheet isn't that hard (once you have got it set up).
The remaining question is why the FEA results found in the OP are significantly different. At the moment I can't see why.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Can this be solved by statics?
I have only just noticed your reply and thought I would acknowledge your effort in writing the spreadsheet to check it out for me - really appreciated, thanks. I've downloaded it and will be giving it a once over, I've wanted to pick up a few tips on programming the stiffness method so it will be really helpful.
RE: Can this be solved by statics?
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Can this be solved by statics?
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Can this be solved by statics?
RE: Can this be solved by statics?