1. Determine the Reactions: Calculate the reactions at the supports of the structural element using equilibrium equations. These reactions represent the forces acting on the element at its supports.
2. Choose a Positive Convention: Decide on a positive convention for the shear force. This convention determines whether upward or downward forces will be considered positive. Commonly, upward forces are taken as positive.
3. Start from a Support: Begin the SFD at one of the supports. Initialize the shear force at the support to zero.
4. Traverse Along the Element: Move along the element from one section to another. At each section:
- Calculate the external loads acting between the current section and the previous section.
- Determine the internal shear force at the current section by adding or subtracting the external loads according to the positive convention.
5. Plot the Shear Forces: Plot the calculated shear forces at their corresponding locations along the element. The resulting graph represents the shear force diagram.
6. Check Equilibrium: Verify that the sum of shear forces along the entire length of the element is equal to the net force acting on the element. This confirms that the SFD is in equilibrium.
Remember to label the coordinate axes, indicate the positive direction of the shear force, and provide appropriate units on the SFD.
The shear force diagram provides valuable information about the internal forces within the structural element. It can be used to determine the critical sections where the maximum shear force occurs, which helps in designing and analyzing structural members to withstand the applied loads safely.