# Quantity calculation of semi round stairs This is a very useful presentation from the renowned engineer Muhammad Ghani for civil engineering students. In this video tutorial, you will learn how to design and work out the quantity of semi round stairs.

The calculation is done based on the following dimensions :-

Linear Length Of Stair = Unknow
Inclined Length Of Stair = Unknown
Waist of stair = 4.5 feet
Thickness of stair waist = 0.41 feet
Riser of stair = 6” = 0.5 feet
Tread of stair = 1’-3” – 1’ (one side & opposite side)
No. of steps = Height / One Riser = 10 feet / 0.5 feet = 20 numbers

Now, it is required to determine the linear length as follow :-
2 (π x R) 0.50 = 2 (3.142 x 9.5) 0.50 = 29.84 feet

Then it is required to determine the inclined length as follow :-
√(Base)2 + (Height)2
√(29.84)2 + (10)2
√(890.42) + (100) = √990.42 = 31.47 feet
So, inclined length = 31.47 feet

Then, you have to find out the waist volume by using the following formula :-
Waist Volume = Lenth x width x Thickness = 31.47 x 4.5 x 0.41 = 58.062 cft
Steps volume = Unknown
Width of tread = 1’ – 3” – 1’ = 1.25 + 1 = 1.125’

Now, it is required to determine one step volume with the following formula :-

One step volume = L x W x H / 2 or Length x Width x Height / 2 (as the steps are in triangular shape)
= 4.5 x 1.125 x 0.5 / 2 = 1.26 cft
So, the volume of one step = 1.26
As the numbers of steps are 20
So, total steps = 20 x 1.26 = 25.2 cft
Total Volume = Volume of waist + Volume of total steps
= 58.062 + 25.2 = 83.26 cft

To get more details, go through the following video tutorial.

Video Source: Civil Study