Understanding Loading Of A Member External Forces / Reactions and Internal Reactions & Stresses

Nov 2019
Hi alll

I was hoping someone could help me a little.

I am trying to understand what happens inside a member when it is loaded - Im actually struggling with some of the definitions.

If i have a simply supported beam that was externally loaded Vertically at the center then i would it be correct to say that there is 2 x external reactions forces which are:-

1) A vertical reaction at the supports
2) A moment reaction at the supports

Below is my diagram (no horizontal forces for simplicity).


Hopefully i am correct so far. Internally there will be 3 x reaction forces which are:-

1) Bending Moment
2) Shear
3) Axial

So i have an external force which generates external reactions at the supports.

These external forces create internal reaction forces.

My question is how does Stress/ Strain factor into this, i know that Stress for example is the internal resistance to external loading - but i am struggling to connect stress to the terms Bending Moment / Shear / Axial.

I was wondering if someone could help explain.

Thank you.