Spiral Staircase with Glass Steps, Zlín, Czech Republic
The goal was to design a spiral staircase with glass steps and railings spanning over 2 floors. With sophisticated anchoring details and helical stringers created from subtle rectangular hollow section, a light and elegant staircase was formed. The interior spiral staircase is located inside of the educational, training and rehabilitation center in the city of Zlín.
Ing. Vítězslav Hapl
Ing. Jan Marik, Ph.D.
Ing. Jan Seifert
|Architectural Design||CUBE DESIGN sro|
|Construction||STAIRS design sro|
Looking from the structural point of view and excluding the rigidity of the reinforced concrete structure, the staircase can be separated into two parts –the 1st to 2nd floor portion and the 2nd to 3rd floor portion. The staircase supporting structure consists of internal and external helical stringers. The stringers are fixed to the landings (welded to the pre-built anchor elements) and to the 1st floor slab (anchored via Hilti adhesive anchors).
The stringers are made of welded closed hollow sections with recessed flanges. The upper flange recess creates a groove for mounting a glass railing, while the lower flange recess is purely an architectural element. The stair treads are made of laminated tempered glass.
The treads are attached to a cantilevered box section (1 inch wide x 1 inch deep) further welded to the stringer web at four locations. The glass tread is supported on the cantilevers by an elastic band and fastened with metric screws. Due to the rigidity of the step-stringer connection, the steps are considered in the computational model.
The inner and outer stringer railings are made of laminated tempered glass bent to the appropriate radius. The railing is inserted into the stringer groove, positioned by elastic spacers, and finally glued into the groove by a suitable elastic material. The railing is considered only as a load and therefore has no load-bearing function.
ModelDue to the above-mentioned staircase floor independence, only one part of the staircase is modeled. The stringers and anchor elements are modeled with plate elements, and the stair treads are modeled as members. To estimate the maximum glass step loading and to evaluate the steel stringer maximum loading, two different stiffness values were used for the glass step connection and the support cantilever. The restraint in the reinforced concrete slab is modeled with a nonlinear failure under tension, elastic support applied to the anchor element’s individual surfaces.
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SHAPE-THIN determines the effective cross-sections according to EN 1993-1-3 and EN 1993-1-5 for cold-formed sections. You can optionally check the geometric conditions for the applicability of the standard specified in EN 1993‑1‑3, Section 5.2.
The effects of local plate buckling are considered according to the method of reduced widths and the possible buckling of stiffeners (instability) is considered for stiffened sections according to EN 1993-1-3, Section 5.5.
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Read more about designing cold-formed sections with SHAPE-THIN and RF-/STEEL Cold-Formed Sections in this technical article: Design of a Thin-Walled, Cold-Formed C-Section According to EN 1993-1-3.
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