FREE VIDEO OF THE MONTH - Civil AM Exam: Structural - Sign Convention

Often when we are using statics to determine internal or external forces and moments of a member, we'll draw dummy forces and moments on our free body diagrams. In doing this, we tend to assume the forces are positive and then flip the direction of the force or moment on the final free body diagram if the value we calculated was negative. It is important to maintain a sign convention especially as we start to explore internal forces. Without a sign convention, you can quickly find yourself at odds as you start to draw shear and moment diagrams.

This video explains the typical sign convention used for beams in flexure. We'll cover the sign convention for internal as well as external forces and moments. Then we'll show how maintaining a sign convention can be used to help keep your shear and moment diagrams consistent.
- Shannon Warchol, PE - DTC Civil Structural Instructor

Shannon Warchol’s Explanation of Sign Convention

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