Loading
/custom-emojis/emojis/contour-map.png
Templates
📚
Articles & Resources
📖
Guides & Support
🎖️
Bounty Program
🌵
CalcTree
On this page you will find a library of calculators that determine the shear force, bending moment and deflection of a single-span beam with different types of applied loading. The calculators are for a simply supported beam or a cantilever beam.
Keep reading this page to discover the theory behind the calculators!

Calculators

  1. Click on one of these calculators below for a specific loading condition on a simply supported beam!

  1. Click on one of these calculators below for a specific loading condition on a cantilever beam!

Beam Analysis Calculator for cantilever beam with trapezoidal load

  1. Click on this calculator that holds up to 10 loads on either a simply supported beam or a cantilever beam!

Beam Analysis Calculator for beam with multiple loads

  1. Explore this other calculator which provides beam analysis for a beam with multiple spans! Beam Analysis Tool

Explanation

Finding SFD and BMD Equations: Macaulay's Theorem

Macaulay's theorem enables us to describe the applied load, shear force diagram (SFD) and bending moment diagram (BMD) for the full length of the beam with single equations.
Macaulay's theorem is a singularity function, which means the function has discontinuities at singular points. Macaulay's theorem says:

For n0xan={0when x < a(xa)nwhen xa\text{For }n\geq0\hspace{1cm}\langle x - a\rangle^n =\begin{cases}0 \hspace{1.58cm} \text{when x < a}\\(x - a)^n \hspace{0.5cm} \text{when x$\geq$a} \end{cases}

For n<0xan=0\text{For }n < 0 \hspace{1cm}\langle x-a\rangle^n = 0
Where:
  1. 
    
    is the position along the beam
  2. 
    
    is the position of the load (or start of the load) on the beam
  1. 
    
    is an integer based on the load applied, with the following categories:
If


If


If


If


It is a Moment
It is a Point Load
It is a Uniformly Distributed Load
It is a Triangular Load / Uniformly Varying Load
  1. 
    
    angle brackets is the notation used for singularity functions. The angle brackets imply that if
    
    then the function goes to zero as there is no effect on the beam due to the load, and if
    
    then there is an effect on the beam so the function is treated as a continuous function
The applied load, shear force and bending moments can be described by singularity functions as tabulated below. You will notice how the applied load equation is integrated once to get the shear force equation and then integrated again to get the bending moment equation. Note the integration rules are slightly different for singularity functions!

Table of Macaulay's Singularity Functions

Loading
Load
Shear
Moment










































🗒️Integration rules for Singularity Functions

Now that we know the singularity functions for each type of force, we can form the

and

equations for our beam. To do this:
  1. Make a section cut just before the right end of the beam, hence ignoring any forces or reactions at the right beam support
  2. Sweep from left to right of your beam's free body diagram and add a singularity function from the table of Macaulay's Singularity Functions each time an applied load or reaction is present
For example, for a simply supported beam with a point load there will be two terms in the equations since there is

reaction force at

and

applied force at

. Use the singularity functions in the second row of the table to form the

and 

equations:






V(x)=Rax00+Fxa0\small{V(x) = R_a\langle x-0\rangle^{0} + F\langle x-a\rangle^{0}}

M(x)=Rax01+Fxa1\small{M(x) = R_a\langle x-0\rangle ^{1} + F\langle x-a\rangle ^{1}}
❗Note, the sign convention used in the Macaulay's Singularity Functions table is consistent with the sign convention used in the calculators. The singularity function for

above is provided as positive (+) even though a downwards load is shown because when values are substituted in the equations, the negative (-) sign shall be included.

Finding Deflection Equations: Double Integration Method

There are three major ways to calculate the deflection equations, but the most convenient is the Double Integration Method.
Using the bending moment equation you created from the Macaulay's theorem, integrating it once gives you the slope equation and integrating a second time gives you the deflection equation. The formulas are given by:
Slope Equation

θ(x)=1EIM(x)dx\theta(x) = \dfrac{1}{EI}\int M(x) \hspace{0.1cm} dx
Deflection Equation

Y(x)=1EIθ(x)dxY(x) = \dfrac{1}{EI} \int \theta(x) \hspace{0.1cm} dx

💡Learn about stiffness,



A common mistake made when integrating is to forget the integration constants. Since there are two integrations there should be a the term

at the end of your

equation.
To find these constants you need to apply boundary conditions (BCs) which differ to each support condition of your beam. A cantilever beam has a fixed support on one end and a simply supported beam has fixed/roller supports at both ends. The boundary condition can be stated as follows:
Cantilever Beam






Simply Supported Beam







Summary

This library of calculators allow you to create the shear force, bending moment and deflection diagrams of either a cantilever or simply supported beam with various loading conditions. Macaulay's theorem, which is the theory behind how the loaded beams are analysed, and how the

,

and

equations are derived is also provided.

Additional Resources

  1. Read more about Macaulay's theorem here!
  1. Access Moment of Inertia Calculators here!
  2. Beam Analysis Tool