Stairs are an important component of a building and often the only means of providing access between the various floors of a building.
The staircase essentially consists of landings and flights. Often, the flight is an inclined slab consisting of risers and treads (collectively called the going of staircase), whereas the landing is a horizontal slab.
From a structural point of view, a staircase consists of slab or beam elements.
Definition of Terms:
| Components of a staircase (a) Plan of staircase (b) Terminology used (c) Part section |
Tread or going of step: Tread is the horizontal upper portion of a step where the foot rests. Going of step is the horizontal distance of the tread minus the nosing.
Nosing: Sometimes, the tread is projected outwards for aesthetics or to provide more space; this projection is called the nosing. Many times, the nosing is provided by the finishing over the concrete tread.
Riser and rise: Rise is the vertical distance between two consecutive treads and riser is the vertical portion of the step.
Flight or going of stair: Flight is a series of steps provided between two landings. Going of stair is the horizontal projection of the flight.
Landing: Landing is the horizontal slab provided between two flights. It is provided every 10–14 steps for comfort in climbing. Landing is also provided when there is a change in the direction of the stairs.
Overlap: The amount by which the nosing of a tread (or landing) over sails the next lower tread (or landing) is called the overlap.
Waist: It is the least thickness of a stair slab.
Winder: The radiating or angular tapering step is called winder.
Soffit: It is the bottom surface of a stair slab.
Headroom: The vertical distance of a line connecting the nosings of all treads and the soffit is referred to as the headroom.
Steps may be of three types as follows:
(a)Brick or concrete steps on inclined slab
(b)Tread-riser steps
(c)Isolated steps
| Type of steps (a) Steps on waist slab (b) Slabless tread-riser (c) Isolated steps |
Types of Staircases:
Some of the most common geometrical configurations are shown in Fig, which include the following:
Plan views of various types of stairs (a) and (b) Straight flight stairs (c) Quarter-turn stairs (d) Half-turn stairs (e) Branching stairs (f) Open-well (half-turn) stairs (g) Open-well stairs with quarter-turn landing (h) Part-circular stairs (i) Spiral stairs (j) Helicoidal stairs |
1.Straight flight stairs with or without intermediate landing.
2.Quarter-turn stairs
3.Half-turn stairs, also referred to as dog-legged or scissor-type stairs
4.Branching stairs
5.Open-well stairs (half-turn) and quarter-turn landing
6.Spiral stairs
7. Helicoidal stairs
Spiral, helical, circular, and elliptical stairs are also referred to as geometrical stairs.
Structural Classification of Stairs:
For design purposes, stairs are classified into the following two types, depending on the predominant direction in which the slab of the stair deflects in flexure.
1.Transversely supported (transverse to the direction of movement in the stair)
2. Longitudinally supported (in the direction of movement)
1.Transversely supported (transverse to the direction of movement in the stair)
2. Longitudinally supported (in the direction of movement)
