Stairs
stair are an essential part of a building's structure. They connect the
different levels and make it possible for people to go up or down much easier than
if they had no help whatsoever in doing so
They are also an important architectural element that contributes to a
building's appearance and how people can move into it.
Types of Stairs
Stairs can be sorted by their shape, use, and patterns of beams. Here
are some popular types.
1.
Straight Stairs: It
comprises a single flight without any break in direction.
Convenient and simple but requires linear space that is lined up.
2.
Dog-Legged Stairs: When
disconnected into two flights by landing makes a 180-degree turn.
It is suitable for transportation in small areas and common in
residential buildings.
3.
L-Shaped Stairs: It
turns 90 degrees at the landing but is similar in other respects to dog-legged
stairs.
Both in appearance and function, it is efficient when built in a corner.
4.
Spiral Stairs: In shape
circular with steps radiating around a central pole.
Less comfortable for people to use on a regular basis than other stairs,
but they also take up less space
5.
U-shaped stairs: Consist of two parallel flights that are
united by a landing and form a U-turn.
Designed for multi-level buildings, they are compact and convenient
6.
Winder Stairs: This
style is similar to L-shaped or U-shaped stairs but it has steps which are
wedge-shaped everyday of the year
Space-efficient but the only dangerous feature
Floating Stairs treads are affixed to walls or hidden conventionally
supported by concealed fittings to produce a feeling of floating.
Modern construction and aesthetics, but it is necessary to include it in
the calculations
Design Example: Dog-Legged Staircase
Problem Statement: Design a dog-legged staircase for a residential building where the
floor-to-floor height is 3.2 meters. The available space is 2.5 m × 4.5 m.
Assume a riser of 160 mm and a tread of 270 mm.
Step 1: Determine the Number of Risers and Treads
- Height
of each riser = 160 mm = 0.16 m
- Number
of risers = Total height / Height of one riser
Number of risers = 3.2 / 0.16 = 20 risers
- Number
of treads = Number of risers - 1 = 20 - 1 = 19 treads
Step 2: Divide the Flights
For a dog-legged staircase, the total number of
risers is divided equally between two flights:
- Risers
per flight = 20 / 2 = 10
- Treads
per flight = 10 - 1 = 9
Step 3: Calculate the Horizontal Dimensions
- Total
run of one flight = Number of treads × Width of tread Total run = 9 × 0.27
= 2.43 m
This fits within the available length of 4.5 m,
leaving space for a 1.5 m landing.
Step 4: Structural Dimensions
- Width
of staircase = 1.2 m (standard for residential buildings)
- Landing
width = Same as staircase width = 1.2 m
Step 5: Reinforcement and Concrete Design
Assume M20 concrete and Fe415 steel for the
staircase.
Slab Thickness:
- Assume
a slab thickness of 150 mm.
Reinforcement:
- Main
reinforcement: 12 mm diameter bars at 150 mm c/c along the flight.
- Distribution
reinforcement: 8 mm diameter bars at 200 mm c/c perpendicular to the main
bars.
Step 6: Check Slope
- Slope
of stairs = Riser / Tread = 160 / 270 = 0.592 (acceptable within standard
limits).
Step 7: Landings
- Reinforcement
in landing slab: Similar to the flight slab, with 12 mm bars at 150 mm c/c
as the main reinforcement.
Final Layout:
- Two
flights with 10 risers each and 9 treads.
- A
landing of 1.5 m between the flights.
- Total
horizontal space = 2.43 m (run of first flight) + 1.5 m (landing) + 2.43 m
(second flight run) = 4.5 m.
- Total vertical height = 3.2 m (achieved by 20 risers of 0.16 m each).
Post a Comment