Spiral Staircase design



Riser "R"
Tread "T"
width of steps and Landing"B"or bw
Inner radius " Ri"
Outer Radius "Ro" = Ri+B
Thickness of slab "h"
Eff. Depth "d"
Plan angle of the stair "α "
Vertical angle at the step 
centreline with horizontal " Φ "
Self Weight of slab
Floor Finish 
weight of steps
Total dead Load "Udl"
Live load
Total service Load "tsl"
Total Ultimate Load "w"
Total Ultimate Load for full width"wu" 
Weight of reinforced concrete "γrc"
Strength of concrete "fc"
Strength of steel "fy"
Clear cover to concrete 
Flexure strength reduction factor
Shear strength reduction factor
Modulus of Elasticity of steel "Es"
Modulus of Elasticity of concrete "Ec"
Modular Ratio "n = Es/Ec"
Dia of top of bars
Dia of bottom of bars
Dia of  closed hoop bars as distribution
Ast top full width
Asb Bottom full width 
Closed hoops per m
Top steel "Ast" mm2
Bottom steel "Asb"mm2
2 legged Closed hoops steel 

Calculation Reference
Concrete Design
Beam Design
Stair Design

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20 Nov 2017
Last Modified
25 Nov 2017
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Comments: 3
tekpekurede 5 years ago
Any text book reference for this calculation. I will be glad to get a reference of PDF file of literature. Many thanks
tekpekurede 5 years ago
How is the Inner Radius calculated? I can not see anywhere on the design for the number of risers. Is the output independent of the number of risers? What does Floor Finish indicate?
JohnDoyle[Admin] 6 years ago
Thanks for another great calculation. Your free lifetime XLC Pro subscription is well deserved.