Using ACI-19 to Analysis and Design a Spiral RC Staircase.

This study aims to reduce the time and effort required to design an economical spiral staircase according to the latest ACI code. Geometrically, the spiral staircase is a complex 3D structure subjected to three forces and three moments. The values of the six internal stresses generated in each section vary along the staircase and are calculated through a series of long and complex equations. By creating six simplified diagrams of all the variable forces and moments, two locally familiar cases were designed: one with a total angle of 240° and other with an angle of 180°. The created diagrams represent the easiest way to find the locations of the maximum forces and moments. Thus, the structural analysis results will be ready for the design according to approved specifications. After creating algorithms based on ACI-19 requirements, the authors designed both cases and drew the details of the reinforcing bars. In comparison, it is considered more appropriate to construct stairs of 180° in residential and commercial buildings because they meet the architectural requirements and are more economical than those of 240°. [ABSTRACT FROM AUTHOR]