Parametric studies on deflection of helical stair slabs

Abstract

A staircase is an essential component of a building and provides pedestrian access to different floors and roofs of a structure. It has unique geometry among all the structural members and requires special consideration in the design. According to the geometrical classification, the helical staircase is challenging as per design considerations because of its complex geometry. They offer, however, a more gradual ascent and descent, making them safer and more comfortable to use than straight stairs. The complex geometry of the helical staircase requires special consideration to understand its behavior in deflection patterns. The work on staircases having simple geometry has been carried out extensively and is available in the literature. However, limited research has been done in the past for helical staircases. The present study is aimed at parametric investigations of helical staircase slab on its deflection behavior. To analyze the effect of stair slab width and landing, two series of staircases were considered. The first model in the study has a central angle of 180° with varying stair slab widths of 1, 1.5, 2, and 2.5 m. In the second series, a landing was inserted at the central part with the same central angle of 180° to study the effect of landing on the results. The results obtained in the form of deflection contour showed an outward leaning tendency with deflection magnitude increasing as moved radially outward. The deflection increased from zero at fixed ends to a maximum at midspan along the inner and outer edges. The deflection ratio for the outer and inner edges was minimum at starting end of the staircase. At midspan, the outer edge is more prone to deflect with greater magnitude. The deflection with varying landing width comparison revealed that the deflection magnitude decreased with increased landing width at the inner edge. The deflection was, however, directly proportional to the staircase slab width at the outer edge. The deflection pattern remained unchanged when the landing was introduced, but the deflection magnitude was found to be increased in all cases.