Civil Engineering Projects

RCC Structures

RCC Structures are nothing but reinforced concrete structures. RCC structure is composed of building components such as Footings, Columns, Beams, Slabs, Staircase etc.

These components are reinforced with steel that give stability to the structure. Staircase is one such important component in a RCC structure.

Dog Legged Stair

In this article, we will discuss different types of staircases and study the RCC design of a dog-legged staircase…

Stairs

Stairs consist of steps arranged in a series for purpose of giving access to different floors of a building. Since a stair is often the only means of communication between the various floors of a building, the location of the stair requires good and careful consideration.

In a residential house, the staircase may be provided near the main entrance.

In a public building, the stairs must be from the main entrance itself and located centrally, to provide quick accessibility to the principal apartments.

All staircases should be adequately lighted and properly ventilated.

Various types of Staircases

• Straight stairs

• Dog-legged stairs

• Open newel stair

• Geometrical stair

RCC design of a Dog-legged staircase

In this type of staircase, the succeeding flights rise in opposite directions. The two flights in plan are not separated by a well. A landing is provided corresponding to the level at which the direction of the flight changes.

Design of Dog-legged Stairs

Based on the direction along which a stair slab span, the stairs maybe classified into the following two types.

1. Stairs spanning horizontally
2. Stairs spanning vertically

Stairs spanning horizontally

These stairs are supported at each side by walls. Stringer beams or at one side by wall or at the other side by a beam.

Loads

• Dead load of a step        = ½ x T x R x 25
• Dead load of waist slab = b x t x 25
• Live load                       = LL (KN/m²)
• Floor finish                    = assume 0.5 KN/m

Stairs spanning Longitudinally

In this, stairs spanning longitudinally, the beam is supported ay top and at the bottom of flights.

Loads

• Self weight of a step          = 1 x R/2 x 25
• Self weight of waist slab  = 1 x t x 25
• Self weight of plan             = 1 x t x 25[(R² + T²)/T]
• Live load                               = LL (KN/m²)
• Floor finish                           = assume 0.5 KN/m

For the efficient design of an RCC stair, we have to first analyse the various loads that are going to be imposed on the stair.

The load calculations will help us determine, how much strength is required to carry the load. The strength bearing capacity of a staircase is determined on the amount of steel and concrete used.

The ratio of steel to concrete has to be as per standards. Steel in the staircase will take the tension imposed on it and the concrete takes up the compression.

These are the essential steps that are to be followed for the RCC Stair Design.

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