Composite structures consist of two different materials joined together in such a way that the resultant strength of the structure is more than the strength of the two materials added together. Due to this composite structure can make best use of each of the constituent materials. In steel and concrete composite beams, concrete is assumed to take most of the compression load while steel takes all the tension. The two materials in the composite structure need to be firmly held together to make the structure rigid and strong.
In steel and concrete composite beams the two materials are held together by means of headed Shear connectors.