Staircase design encompasses three primary scenarios, each necessitating a unique structural approach:
Longitudinally Spanning Stairs: These stairs span solely between landings, lacking any lateral support. In this configuration, the staircase is designed as a beam supported at its ends by the landings. The primary reinforcement is placed at the bottom of the stair slabs to withstand the tensile forces generated by the bending moment.
Transversely Spanning Stairs: This type of staircase relies on sidewalls or stringer beams for support. If supported by sidewalls alone, the staircase functions as a cantilever beam, with the main reinforcement concentrated on the top surface of the slab to resist tensile forces. When both sidewalls and a stringer beam are present, the staircase is designed as a transversely spanning beam, supported at both ends. In this case, reinforcement is placed at the bottom of the staircase to handle the bending stresses.
Stairs Resting on Solid Support: In this scenario, the staircase is directly supported by a solid foundation, eliminating the need for complex structural calculations. Minimal reinforcement is required, primarily to control thermal and shrinkage cracking, as the primary load-bearing capacity is provided by the underlying support.
Understanding these distinct design scenarios is crucial for ensuring the safety and stability of staircases. By tailoring the structural approach to the specific support conditions, engineers can create efficient and durable staircase designs.