How Do You Calculate Bending Stress and Moment on an I-Section Beam?

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Discussion Overview

The discussion revolves around calculating bending stress and moment on an I-section beam, specifically focusing on a beam with given dimensions and loading conditions. Participants explore theoretical and practical approaches to solving the problem, including relevant equations and methodologies.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant requests help with calculating the maximum bending moment, minimum bending stress, and radius of curvature for a specified I-section beam under a uniformly distributed load.
  • Another participant suggests that the original poster should list relevant equations and show their work for others to check, indicating a need for foundational knowledge.
  • A different participant recommends using a software tool, 'DTBeam', to perform the calculations, implying that theoretical understanding may not be necessary for practical application.
  • One participant corrects the original poster's terminology from "min bending stress" to "max bending stress," referencing a textbook that covers the necessary equations and principles.
  • Another participant recalls that the maximum bending moment occurs at the midpoint of the beam and provides a formula involving reaction forces and uniformly distributed load for calculating it.

Areas of Agreement / Disagreement

Participants express varying levels of knowledge and approaches to the problem, with no consensus on the best method to solve the calculations. Some emphasize the need for theoretical understanding, while others suggest practical tools.

Contextual Notes

There is uncertainty regarding the specific equations and methods to be used, as well as potential dependencies on the definitions of terms and assumptions made in the calculations.

Who May Find This Useful

This discussion may be useful for students and practitioners in structural engineering or mechanics who are looking for guidance on calculating bending stress and moment in beams.

the_karlos
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an i section beam 5 meters long, supported both ends,
with a 2nd moment of area 120x10 ^-6 m ^4

a depth of 250mm and a uniformaly distributed load of 20KN/m

caculate,
max bending moment
min bending stress
the radius of curvature of the beam where the bending moment is maxaimun ( E-210GPa)



people i not got a clue, its some last min work that's been droped on me!

any working or help would be amazing
 
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Hello, the_karlos. You must list relevant equations yourself, and show your work; then someone might check your math. Look in your textbook to find relevant equations.
 
Hello there,

If you don't have the theoretical knowledge required, just Google search 'DTBeam' and download the demo version. It will do all the required calculations for you.
 
Irshaad.K said:
Hello there,

If you don't have the theoretical knowledge required, just Google search 'DTBeam' and download the demo version. It will do all the required calculations for you.

For real, it would take days just to explain the last question.
 
min bending stress
should probably read
max bending stress

I do not know what textbooks you use for the course, but Chapter IV of the classic book derives all the required equations above from first principles and has worked examples very similar to the simple case you mentioned.
The reference should be easily available from your college/university library:

Strength of Materials, Part I, Elementary Theory and Problems, D. Van Nostrand Company, 1st Ed. 1930, 2nd Ed. 1940, 3rd Ed. 1955
or on Amazon:
https://www.amazon.com/dp/0898746213/?tag=pfamazon01-20
 
Last edited by a moderator:
it has been a while since i covered structural mechanics but I am sure i can remember that the maximum bending moment occurs at the middle point of the beam and the calc should include (Ra x 1/2l) - (UDL x 1/2b x 1/4l) < try that and let me know how you get on

Ra = reaction
L = length of beam
 

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