A spiral concrete staircase is considered quite a complex member. It must carry various kinds of forces simultaneously: bending, shear, axial force, and torsion. The member can't be independently treated as a compression or bending member. Instead, we need to consider all forces acting at critical sections.
Lake side village project: designed by ALPS Consultants
Lake side village project: designed by ALPS Consultants
Here are some spiral concrete staircases we designed for a residential project. To analyze and design such stairs, one important thing not to overlook is its foundation. A large amount of vertical force and bending moment must be transferred safely to the foundation to provide firm support for the stair. Next, the stair might be modeled accurately by a 3d structural analysis. The element can be modeled as a space frame to gather all occurring forces. Finally, reinforcements are determined at the critical section at support and mid-span for properly combined axial-flexural and shear with torsion.