Bending Moment and Fixed Moment Calculations

Bending Moment and Shear Force diagrams

What is Bending Moment?

The element bends when a moment is applied to it. Every structural element has bending moment. Concept of bending moment is very important in the field of engineering especially Civil engineering and Mechanical Engineering.

Unit of measurement: Newton-metres (N-m) or pound-foot or foot-pound (

Bending moment is directly proportional to tensile and compressive stresses. Increase in tensile and compressive stresses results in the increase in the bending moment. These stresses also depend on the second moment of area of the cross section of the element.

What is Shear stress?

Shear stress is defined as the measure of force per unit area. Shear stress occurs in shear plane. There are many planes possible at any point in a structure which can be defined to measure stress.

Stress = Force/Unit area

Example: Bending Moment and Shear Force Calculations

Frame diagrams | Bending moment and shear force calculations

Frame diagrams | Bending moment and shear force calculations

Simply supported bending moment

Mab = wl2/8 = (22×4.14×4.14)/8

= 47.13 KN-m

Mbc = wl2/8 = (22×4.14×4.14)/8

= 47.13 KN-m

Fixed Moments

Moment about B

wl2/12 = (22×4.14×4.14)/12

= 31.4 KN-m

Support reactions

RA+RB+RC = 2(22×4.14)

= 182.16 KN

3RA = 182.16

RA = 60.72KN

RA = RB = RC = 60.72 KN

Also check out: Introduction to Load Calculations

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  1. #1 by kamal jakariya on October 31, 2014 - 2:41 pm

    i need bending moment diagram books

  2. #2 by george on November 27, 2012 - 1:23 am

    hw did we get the 30.36kn for the shear force diagram

  3. #3 by Azeez on April 10, 2012 - 10:07 am

    me a diploma engineer, interested in structural designing, It will be very helpful if you post a complete structural analysis and design of any G+2 framed structure including load calculation, bending moment, etc. thank you in advance

  4. #4 by kehinde on February 26, 2012 - 12:55 am

    Please, I need assistance in the use of Moment distribution method for designing beams, slabs,etc. I don’t have a firm grip of the basics, kindly open my eyes to the nitty gritty… tnx

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