Simplified procedures on how to design a stair cases in morden ways.
Introduction
Stair is the among of the structural elements of the building or any structure that alllows movement and circulation in the building. There different types of stairs, For example these are types of stairs according to their geometrical view. These are;
i). Straight stairs
ii). Quater turning stairs
iii). Half turning stairs
iv). Branching stairs
v). Open wells half, or quater turns
vi). Spiral stairs
Also stairs can be classified intro structural uses as follows, The stair can be;
a). Transverse stairs - The stair which loading is spanning at right angle to the flight direction
b). Longitudinal stairs - The stair in which loading is spanning in parallel direction to the flight direction.
Procedures on how to design a staircase.
The following are the general procedures on how to design a staircase in simple way, This is mainly based on BS 8110-1:1997. Consider an image below,
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| Design of stair by Mbedule design |
1. Loading calculation.
Loading calculation on stairs depending on the type of stair basing on structural considerations as follows.
In transverse staircase loading can be found as follows.
Dead load for the step = Density of concrete times cross section area of a single store.
Note the cross section area of the step should be calculated as taht of triangle
Dead load for the waist = Density of concrete times the cross section area of the soffit.
After getting the values of dead loads of soffit and the step you should add them so as to get total dead load that will be multiplied by 1.4 factor for loading in dead loads
In longitudinal spanning staircases dead load can be found as follows.
Dead load for the soffit = Density of concrete times the cross section of the soffit
Dead load for step = Density of concrte time the cross section area of the step plus the ( density of concrete times the waist) divide by cos of angle of inclinationation.
Also after getting the above dead loads you need also to add so as to get total dead load.
- Not only dead load will be calculated but also live load will bve calculated. Both dead and live loads are just kept in KN/M^2, uniformly distributed loads.
2. Bending moment calculations.
In calculating bending moment there are things to be considered in type of support as well as load distributrion, This is described as follows;
- Bending moment for simply supported stair with uniformly distributed load.
= (WL^2)/8
- Bending moment for cantilever stair
=(WL^2)/2
- Bending moment for continous stair with slab end at one support, have two moments as follows
a). Span moment
= 0.11WL^2
b). Support moment
= 0.11WL^2
- Bending moment for a continous stairs to its ends
a). Span moment
= 0.1WL^2
b). Support moment
= 0.1WL^2
Where by "W" is the uniformly distribnuted load iobtained in loading calculation, and "L" is the effictive span of the staircase. Using that moment you can simply use softwares to obatain the sizes of reiforcement on your stair,
3. Using the loading calculated in various softwares for structural engineers.
These spftwares are like Microstation, Microsoft projects, ETABS, Autodesk Revit and prota structures.
