Question

Compare the bending moment diagrams of the indeterminate and simply supported beams. What are the advantages of using indeterminate beams? Why are thereactions different from those of the simply suppored beam with similar loading

Answer 1

Simply Supported Beam:

Simply supported beam is statically determinate structure which has mainly two supports at the ends, one support should be fixed and another could be fixed or roller support. The load is applied on the beam depending on the type of loads such point load,uniformally distributed load, and uniformally varrying load.

Continuous Beam:

A continuous beam is a statically indeterminate structure. They rest over three or more supports, thereby having one or more redundant support reactions.

Comparision of bending moment diagram of continuous beam and simply supported beam:

• The maximum bending moment in continuous beam is much less than that in simply supported beam of same span carrying same load.
• Average bending moment in continuous beam is also less than that in simply supported beam .

Advantages of using continuous beam over simply supported beam:

• For the same span and section, vertical load capacity is more.
• Mid span deflection is less.
• Lighter material for the construction can be used to resist the bending moment.

In simply supported beam which is statically determinate beam, equilibrium conditions are fully adequate to analyze the structure and extra conditions like compatibility of displacements are not required to analyze the structure. But in continuous beam ( statically indeterminate structure ) conditions of equilibrium are not adequate to fully analyze the structure and extra conditions like compatibility of displacements are required to analyze the structure along with the equilibrium equations.

There is no stresse produced due to lack of fits in simply supported beam but lack of fits produces stresses in continuous beam.

Bending moment or shear force at any section in simply supported beam are independent of material properties of beam and cross section of the beam but depends upon the same for continuous beam or statically indeterminate beam.