These stairs are also known as moving stairs or even moving flights. By a revolving drum, the escalator is kept in motion. A few steps at top and bottom are kept level through moving individually. A person has to occupy a step (preferably the first step) of the escalator for the upward or downward motion.
Essential features of the escalators are discussed below.
21.9.1 Essential Parts of Escalator
An escalator comprises of three parts, viz., steel trussed framework, hand rails and an endless belt with steps. Accurately arranged tracks are attached to the steel trusses and the steps move on these tracks.
21.9.2 Speed and Slope of Escalator
Speed of the escalator is normally 45 cm per second. The pitch or slope of the inclined bridge is kept at 30°. The moving stair is in the form of an inclined bridge between two successive floors.
21.9.3 Location of Escalator
It is necessary to make a careful study of flow of traffic before deciding the position of the moving stair. In a new structure the escalator has to be fixed at a position where the traffic is likely to be the heaviest.
21.9.4 Design Aspects of Escalator
The anticipated load on the escalator has to be properly assessed before design. The main factor which affects the design is the floor-to-floor height. The stair way should be kept independent by providing a structural framework around the stair well. The structural frame is designed to take care of the load of floor, hand rail, etc.
21.9.5 Installation
The various parts of the moving stair are fabricated in a workshop and installed at the location. Adequate care has to be exercised while installing each part. This arrangement ensures smooth working of the morning stair. Generally, escalators are fixed in pairs, one for upward movement and the other for downward movement. The escalators may be positioned diagonally opposite to each other or parallel to each other.
Example 21.1
The staircase room available in a residential building is 1.4 m × 4.8 m. The head room available is 3.2 m. Draw a lay-out plan of the stairs.
Solution:
As the space available is only 1.4 m, the width of staircase be taken as 1.4 m and no turn can be provided. Further the length of the stair is 4.8 m only and a landing can not be provided. Thus a straight-flight staircase be provided.
A rise of 20 cm is assumed
No. of risers (R) 
∴ No. of treads (T ) 
Width of tread is assumed as 25 cm
Space for passage = 4.8 – 3.75 = 1.05 m
The layout is shown in Fig. 21.18
Figure 21.18
Example 21.2
A dog-legged staircase has to be provided in an office building. The staircase room is of 3.0 m × 6.0 m. The distance between the floors is 8.5 m. Design the stair-case and draw the lay-out plan.
Solution:
Width of stair is assumed as 1.4 m. As the width of the staircase is 3 m, a half space landing is provided with two flights. The width of landing is made equal to width of the stair.
Height of each flight 
A riser of 15 cm is assumed
No. of risers (R) 
Exact rise of each step 
No. of treads to be provided in each flight
T = R – 1 = 12 – 1 = 11
Tread is taken as 30 cm
Here 15 cm × 30 cm step satisfies all the rules.
Space left for passage = 6 – 3.6 = 2.4 m.
The lay-out plan is shown in Fig. 21.19.
Figure 21.19
Example 21.3
It is intended to provide a suitable staircase for a hospital which consists of ground floor and first floor. The details are
Staircase room size = 6.0 m × 4.3 m
Height of each floor = 3.5 m
Thickness of floor slab = 15 cm
Width of stair = 140 cm
Provide a provision for lift.
Solution
An open-newel stair may be designed. The space of the well may be utilized for provision of a lift.
As in Example 21.2, adopt a rise of 15 cm and a tread of 30 cm.
Then, 
Provide 10 steps in the first flight, 5 steps in the second flight and 8 steps in third flight.
Figure 21.20 shows the lay-out plan of the staircase.
Figure 21.20 Staircase 600 cm × 430 cm
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