Checking the supporting reactions of the beam

The verification of the found values ​​of the reactions of the supports can be carried out using the equation of the sum of the moments with respect to any other point, for example, B.

The magnitude and direction of the supporting beam reactions are determined

If we substitute the obtained values ​​in the equation, the sum of the moments will be zero, then the support reactions have been found correctly.

The check equation for the sum of the moments for a two-support beam
Note: In the equation of the sum of the moments, in contrast to the forces, the moments applied at the point relative to which the equation is made are always written down.

Here, the value of 0.1kNm in the sum of the moments was obtained by rounding the values ​​of the found reactions to one decimal place, and shows the correctness of the calculations.

Video lessons on the definition of support reactions

A positive sign of the magnitude of the support reactions suggests that their direction was originally chosen correctly.

Video by subject (contains English subtitles)

If the found value of the reaction turns out to be negative, it must be directed in the opposite direction by changing the sign to «+».

Construction of Q and M diagrams for a beam >

Теория и решение задач по теормеху, сопромату, технической и прикладной механике, ТММ и ДетМаш