A steel-in-concrete composite structure is a mixed material framework with steel beams wrapped or encased in concrete. Very often this is accompanied by a core or shear wall built exclusively of reinforced concrete, so it may share properties of a tandem frame.

This type of frame is usually used for very large buildings such as skyscrapers and supertalls. It is employed much more commonly in Asia than in other parts of the world.

The concrete lies around the steel framing member. In a concrete-in-steel composite arrangement, concrete instead fills a hollow steel member.