A concrete-steel tandem structure is a very common type of mixed material framework, in which the concrete elements and steel beams are attached to each other side-by-side. Often this takes the form of a concrete core surrounded by steel beams. It can also be a concrete framework with steel outrigger beams added for increased strength.

The concrete and steel framing elements remain separate components attached alongside one another. Their combined structural action differs from steel members encased in, or filled with, concrete.

A stacked concrete-and-steel frame places the different frameworks at successive floor levels. A tandem arrangement has the materials working together side by side.