Stair, types of stair, design of dog ledged stair and stair design excel sheet download.

Stair

Stairs are vital structural and functional components in buildings, enabling vertical movement between different levels.

They are also significant architectural elements, contributing to the aesthetics and accessibility of a structure.

Types of Stairs

Stairs can be categorized based on their design, function, and layout. Here are some common types:

1. Straight Stairs:
• Consist of a single flight without any change in direction.
• Simple and economical but require more linear space.
2. Dog-Legged Stairs:
• Consist of two flights separated by a landing, making a 180-degree turn.
• Suitable for small spaces and commonly used in residential and commercial buildings.
3. L-Shaped Stairs:
• Similar to dog-legged stairs but turn 90 degrees at the landing.
• Aesthetic and efficient in corner spaces.
4. Spiral Stairs:
• Circular in shape with steps radiating around a central pole.
• Space-saving and visually appealing but less comfortable for frequent use.
5. U-Shaped Stairs:
• Feature two parallel flights connected by a landing, creating a U-turn.
• Compact and functional for multi-level buildings.
6. Winder Stairs:
• Similar to L-shaped or U-shaped stairs but with wedge-shaped steps instead of a landing.
• Space-efficient but less safe compared to stairs with landings.
7. Floating Stairs:
• Have treads fixed to the wall or supported by hidden structures, giving a floating appearance.
• Modern and aesthetic but require precise engineering.

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).

---

                                                              UnZip PW: digitaldeni