What is the difference between a simply supported beam and a continuous beam?

What is the difference between a simply supported beam and a continuous beam?

 A simply supported beam and continuous beam are the beams having different support conditions.

Simply supported beam: A simply supported beam is the one which has hinged support at one end and a roller support at the other end. Hinged support is provided so that no moment could act on the support and, roller support is provided such that there should be no axial(horizontal) force on the member.

Continuous beam: A continuous beam is the one which has hinged support at one end and more than one roller support in the entire span. The hinged support is used to bear horizontal and vertical forces with zero moment at end support. Other roller supports will experience vertical reaction only. Here bending moment act in the beam above intermediate support(except extreme end supports).

Note: A continuous beam can have a variety of intermediate supports.

Why is it used?

A simply supported beam is used when we have to transfer the load to the support in the form of linear reaction only(not bending moment). In this case beam has zero bending moment at supports.

A continuous beam is used when the span is large enough and construction of component in fragment is either not plausible or is not economical. In this case beam carries a non-zero moment at intermediate supports.

Note: There is a case of overhang continuous beam also, in which end is not supported(cantilevered). In this case the last support should not be treated as end support, instead end support is the one that is located at extreme end point of the beam.