Guide to Design of Simple Beam | Design of Steel Structures





Design of Simple Beam

A member carrying loads perpendicular to its axis is defined as a beam.

For a simple floor beam, I-sections are used.

M/I = (sigma) /y

M = (I/y)(sigma)

I/y = Z (section modulus)

Therefore, M = z(sigma)

When beams are loaded, bending stresses are developed at all sections.

The bending stresses developed in beams can be determined by the equation theory of simple bending.

For laterally supported beams, the permissible bending stress in tension as well as in compression should not exceed (sigma)bc or (sigma)bt = 0.66fy

For laterally unsupported beams, the permissible stress in bending compression is calculated by using tables from the the IS code book (IS:800).

Load carrying capacity of the Beam

From structural steel tables for the given beam, the section modulus (Zxx) is obtained.

Depending upon whether the beam is laterally restrained or unrestrained; the value of permissible stress in bending compression ((sigma)bc) is calculated.

The moment of resistance of the beam is found out.

MR = Zxx .(sigma)bc

Equating the moment of resistance to the maximum bending moment equation, the total load (w) the beam can carry is calculated.



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  1. #1 by back to school on October 18, 2010 - 2:14 pm

    Simple but logical. Excellent derivation

  2. #2 by Harvard Reference Generator on October 19, 2010 - 1:55 am

    A good explanation, many thanks.

  3. #3 by yoganarasimha swamy on May 25, 2011 - 6:25 am

    good, internet search should give this type of notes and theory
    thanking you

  4. #4 by yoganarasimha swamy on May 25, 2011 - 6:28 am

    good , interesting

  5. #5 by Poonguzhale.V on September 30, 2011 - 4:13 am

    Thank u. This makes us to understand in a easy and simple way. Thanks a lot.

    • #6 by BenzuJK on September 30, 2011 - 11:52 pm

      Hello Poonguzhale.V,
      I am glad our articles were helpful. Do keep visiting. We shall keep posting technical and informative article that will be helpful to all Civil Engineering and Architectural Community.

    • #7 by Faisal Hayat on January 11, 2012 - 10:39 am

      Simple very interesting

      • #8 by Harish on March 7, 2012 - 3:46 am

        thankyou for providing this website

  6. #9 by vijay mantha on February 7, 2012 - 11:31 pm

    can anyone tell me about the various effective length conditions in columns design and as well as various support conditions in slab design in details

  7. #10 by amantle kaisara on March 7, 2012 - 10:01 am

    i was given an assignment in structural engineering class that states that i have to design a beam and a column for a two story building so please i need help.the assignment is to submitted on the 15th of march 2012 next week…………

  8. #12 by Ajith on April 7, 2012 - 12:18 am

    I have a doubt about beam design. It is about a question in which it is asked to design a beam(Not specified whether it is an R.C.C or Steel beam).The span and self wt are given.It is told that the beam is laterally supported throughout. Please clear my doubt that whether the Question is an R.C.C design or steel design.

  9. #13 by Jocelyn on February 4, 2013 - 5:56 pm

    very interesting…

    reasons for adding beams while on going construction?

    • #14 by BenzuJK on February 9, 2013 - 7:49 am

      Columns and beams are like the anatomy of the building. It is not called adding beams. It called constructing beams so that walls could be built on top of it and enable the structure to take its load.

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