Question

Explain how the positive and negative bending moment in the beam is accounted in the construction of the beam.

Answer 1

Bending moment in beam is responsible for hogging and sagging of the beam.Negative Bending moment in beam causes hogging whereas Positive Bending moment in Beam causes Sagging.

Bending moments are counteracted in beams by providing reinforcements .

Bending of bars is done for Bending moment in beams.

Slabs exert load on the beams , due to their load , a positive bending moment develops on the mid or center of a beam which causes sagging .In order to counteract this the tension reinforcement are provided at the bottom of the beam.

In the same way , a negative bending moment develops on the ends which causes hogging.For this , the bars or tension reinforcement are provided at the top part of the beam .

The bars or reinforcement is provided in the beam in such a way that it is bent both ways ,to counteract negative bending moment at the end span of the beam and positive bending moment at the mid span of the beam.