Bending Moment

Definition - What does Bending Moment mean?

A bending moment is a force that causes an object such as a pipe to bend. The bending effect is caused by the applied force at a given distance from a reference point. The greatest force of bending will be experienced at the point where the force is applied. Inadequate restraint will also cause the pipe to rotate about a certain point. A bending moment is observed in drill pipes used in the horizontal directional drilling (HDD) process.

One side of the thread connection experiences tension and the other side compression when the bending moment occurs.

Trenchlesspedia explains Bending Moment

When a bending moment increases, the tensile and compressive strength also increase but also depend on the second moment of area or the cross-section of the pipe. When the bending moment is large enough it causes the tensile stress of the pipe material to become greater than its yield stress throughout its cross-section, and failure in bending takes place. A bending moment is calculated from a reference point by multiplying the magnitude of the force by the distance of the force from the reference point. Bending moments also affect buried pipes depending on the loading it experiences.

Flexible pipe materials, such as high density polyethylene (HDPE) or polyvinyl chloride (PVC), are better able to resist bending moments compared to rigid pipe materials such as cast iron (CI) and concrete.

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