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SUMMARY

This discussion focuses on solving the reactions for a fixed cantilever beam subjected to multiple loads. The beam has a total length of 16 feet, with a 2000 lbs load at the left end and a 1000 lbs load positioned 10 feet from the left. The user initially calculated reaction forces at supports A and B but encountered discrepancies, particularly with the torque moment at B. The solution involves using the flexibility or integration method to analyze the indeterminate beam problem, emphasizing the importance of accurately determining reaction forces and moments.

PREREQUISITES
  • Understanding of fixed and roller support reactions in beam mechanics
  • Familiarity with the concepts of shear force and bending moment diagrams
  • Knowledge of the flexibility and integration methods for solving indeterminate beams
  • Basic principles of structural analysis, including moment summation
NEXT STEPS
  • Study the flexibility method for analyzing indeterminate beams
  • Learn how to construct shear force and bending moment diagrams for cantilever beams
  • Review the differential equation of the deflection curve for beam analysis
  • Examine examples of similar beam problems in structural analysis textbooks or PDFs
USEFUL FOR

Structural engineers, civil engineering students, and anyone involved in analyzing cantilever beams and understanding reaction forces in structural systems.

EQ
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Cant upload the right pic but kinda got a diagram up.
 
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I need help finding reactions for a fixed cantilever. total length is 16ft and its fixed on the right side. The loads on it going from left to right. 2000 lbs at the end of the left. 1000 lbs 10ft from left. There is one support for the cantilever and its where A is at which is 6 ft from left. The dimension for the 1000 lb load is 6ft from B which is the fixed point of the cantilever.

I've been summing the moments at A and B and my numbers are 3800 at A and 800 at B with a zero torque moment at B which is not right, it has to have a torque moment.

Please help if you can.


2000...10ft...1000...6ft...
|
|_______________|_________ B Fixed End
...6ft... A .....10ft...


Thanks
 
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If "A" is a roller and has one reaction, and "B" is fixed for 2 translations and 1 rotation, then that is an indeterminate problem. You will need additional beam properties to be able to solve it.
 
Don't double post, cyclovenom already gave you a response.
 
haynewp said:
If "A" is a roller and has one reaction, and "B" is fixed for 2 translations and 1 rotation, then that is an indeterminate problem. You will need additional beam properties to be able to solve it.


I should'nt need additional beam properties to solve the reactions for the loading conditions.

For the rotation at B it should just be the sum of the moments correct?

After getting the reactions. I would be able to get a V max and M max from diagrams.

Please clarify.
 
You need to post a real picture. Thats a joke, sorry.
 
There are a couple of ways to solve an indeterminate beam problem. If you were not given the moment of inertia or modulus of elasticity, then the "flexibility" or "integration" method would be the one I would use to give you the approximate answers, since the E and I for this problem are likely to cancel out.
 
This is a hyperstatic system solved by differential equation of the deflexion curve. So what you should do is express reactionary moment in terms of the reaction at support A, and the reactionary force in B in terms of the reaction at support A, then start making your sections (bending moment equations).

If you want further help than that, Show your work.
 
I believe that is the same as what I am calling the integration method:

Either way, the assumption has to be made that the shear deformation is negligible compared to flexural deformation, or else you would need additional beam properties to get the correct solution.
 
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  • #10
Yes haynewp, we are talking about the same method.

EQ, Check pages 15-19 of the PDF haynewp provided. There's a similar problem like yours
 
  • #11
Cyclovenom said:
Yes haynewp, we are talking about the same method.

EQ, Check pages 15-19 of the PDF haynewp provided. There's a similar problem like yours


Thanks for the help guys. I figured my problem, I didn't get my reaction right at B its negative not positve which threw off my shear diagram.

For deflection I did moment by parts.
 

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