Estimating Sheet

# How to determine whether a beam is determinate or indeterminate

Construction Software In this construction video tutorial, you will come to know about definition of determinate and indeterminate beam as well as the criterion for verifying whether a beam is determinate or indeterminate.

It should be noted that a beam is called determinate beam if equilibrium equations are used to completely analyze that beam. Given below, the details of equilibrium equations :-

∑Fx= 0 (some of the forces in x direction should be zero)
∑Fy= 0 (some of the forces in y direction should be zero)
∑Ma= 0 (some of the forces at point a should be zero)

A beam is called indeterminate beam when it is not possible to analyze it completely by applying only equilibrium equations.

The following formulas are applied to define whether a beam is determinate or indeterminate :-

If R = 3n, the beam will be defined as Determinate beam

If R is greater then 3n, then the beam will defined as indeterminate beam
If R is less then 3n, beam will be defined as Not stable

Here,

R denotes number of unknown reactions.
n denotes number of beam segments
and 3 belongs to equilibrium equations

To get more details, watch the following video tutorial presented by S.L. Khan. 