The two-way concrete structural system includes which of the following types?

The two-way concrete structural system is characterized by the way it supports loads and transmits them in two directions, distributing the forces across the slab. Both flat plates and waffle slabs are excellent examples of this system.

Flat plates are concrete slabs that have no beams, relying solely on the slab itself for support. They distribute loads in two directions, making them an efficient choice for certain building types, especially where architectural flexibility and lower floors height are desired.

Waffle slabs, on the other hand, are a more complex system that also consists of a flat slab but is reinforced with a grid of ribs on the underside. This configuration allows for greater spanning capabilities and reduced dead weight, while still facilitating load distribution in both directions.

Because both flat plates and waffle slabs are integral parts of the two-way concrete structural system, the answer correctly identifies that both types fall under this category. This understanding is key for architects and engineers when making choices for structural designs, as they need to consider load distribution, architectural intent, and material efficiency.