The Structure of a building is in Reinforced Cement Concrete.
The steel bars provided in the concrete make it strong to carry the tensile forces.
Thses bars are called as REINFORCEMENT.
The detailing of these bars [ Diameter ,spacing,covers, laps , dowel lengths, development lengths and shapes } are provided by RCC designer and are specified in the RCC drawing.
The extract of the steel reinforcement in the form of a table is known as Bar bending Schedule. The tabulation of the reinforcement details can be conviniently done using the MS Excel.
Professional contracting firms have got printed formats for BBS ready for the use of their staff. The BBS is prepared by the Qauntity Surveyors during estimation . The BBS is also prepared by the Site Engineers for controlling the quality of the Reinforcement Bars at site. The BBS is also an excellent tool for recording the measurements of the Reinforcement bars at site and the BBS can also be used to submit the Bills for the Reinf..bars.
This is a chart which basically gives the micro details about the various bars. This gives the dia, shape of bar , cutting length of the various bars in a RCC element such as Footing, column , beam ,slab etc.
The site engineer prepares the BBS based on the drawing and after due verification , hands it over to the reinforcement fitter.
By the use of BBS , the weight of the Re-bars can be easily calculated.
Let me explain you this popular tool with an example.
Imagine , there is a beam of the following cross section.
The details of the reinforcement have been tabulated in the following table :
The cutting lengths of each bar is calculated and tabulated as follows :
But you can see that many details are missing from this abstract. Hence , a better tabulation , known as the BBS has been prepared which gives each details of the Re-bar in a crystal clear method :
The bar bending gives a very clear picture of the reinforcement.
You would have heard people mentioning different units such as Acres , Hectors , Ares or Square Meters or
Square yards in reference to the land. Similarly you would be knowing Inch, foot, Meters ,Yards and Millimeters
as being used in connection with lengths.
These units mentioned above do , in fact , belong to two different systems of measurements called
English system of measurements and Metric system of measurements
( Read this web resource on : British & Metric systems )
For a person working in the construction field, it is essential to have a complete knowledge about
both these measurements systems ; The English and the Metric .
This article explains both the units , their brief history andalso discusses the
basic reasons as to why both these systems must be equally understood.
2 Basics :
In this article , we shall only discuss about the units for length , area and volume . Before we go further ,
let us revise our basic knowledge :
2.1 . Any physical object has three dimensions. length , width and Depth .
Width ( W ) is sometime written as Breadth ( B )
2.2 . The Depth ( D ) can be written as Height ( H ) or some times as Thickness ( T ).
For example , if it is a building , we shall write :
2.3. Length , Width and Height of a building .
( Width and Breadth are synonyms and can be interchanged )
2.4 . If it is a steel plate , we shall write :
Length , Width and Thickness .
2.5 . Thickness or Height both are measured in vertical direction . As a convention , for a small object like a brick ,
we shall mention the thickness whereas for a larger object , such as a room , we shall mention the height.
2.6. The word Depth is also related to the vertical direction but is used for indicating a
vertical dimension which is going lower than where we are standing.
3. Length , Area and Volumes :
3.1 Linear dimensions :
Length : The longest horizontal dimension of an object is called length.
Width or Breadth : The smaller horizontal dimension is called as Width or Breadth
Depth or Height or Thickness : the third dimension which is measured in the vertical axis is mentioned as Depth or Height or Thickness
3.2 Area :
It is the product of two dimensions of adjoining side .
For example , if a rectangular plot has a length of A and width of B , the area is given by :
Area = A x B
3.3 Volume :
It is the product of three dimensions of an object .
For example , if the 3 dimensions of a truck are : a , b and c ,
Volume = a x b x c .
4. The British or English systems of Measurements :
For length : Inch , Foot , Yard or Mile
For Area : Square Inch , Square Foot , Square Yard , Square Mile
For Volume : Cubic Inch , Cubic Foot , Cubic Yard , Cubic Mile
4.1 For construction purpose , we normally use :
For Length : Inch , Foot ,
For Area : Square Foot ,
For Volume :Cubic Foot ,
5. The Metric systems of Measurements :
For Length : Millimeter , Centimeter , Meter and Kilometer
For Area : Square Millimeter , Square Centimeter , Square Meter , Square Kilo Meter
For Volume : Cubic Millimeter , Cubic Centimeter , Cubic Meter , Cubic Kilo Meter
5.1 For construction purpose , we normally use :
For Length : Millimeter , Centimeter , Meter
For Area : Square Meter
For Volume : Cubic Meter
6. Direct measurement : Length or Width or height of an object can be measured with a measuring tape
( Inch , Foot or Millimeter , Centimeter , Meter .) but Area or Volumes have to be calculated with the formula as mentioned above .
Thus , Area or Volumes are Derived from the linear measurements
7. Why a construction person needs to know both the English and Metric systems ?
This is simply because both of these measurement systems are prevailing at the site of construction .
Let us take a few examples which shall clarify this point :
7.1 While discussing about a plot or showing it to a customer , the plot area is mentioned in Square Yards
( This is actually a Chauras Var but in colloquial language , it is called VAR only. )
or Guntha or Acres but when you refer to the government documentation for the same plot ,
the plot area shall be recorded in Metric units such as either Square meters or Are or Hectors.
7.2 The drawings given by Architect or RCC consultant shall be necessarily in Metric units ( mm , cm or meter ) and thus , all quantities worked out shall be either in Square Meters or Cubic meters.
However, when buying the materials at the site , the rates for murrum , sand and aggregate are quoted by the supplier in British units only
( In Brass which means 100 Cubic Foot ).
7.3 The rates quoted by the RCC / Masonry and plastering contractor shall also be in British units only . ( Per Square Foot of the built up area )
7.4 While the area of the flats to be sold shall be described by the builder in British units ( Square foot of carpet area or built up area ) , while transferring the sold flat to the customer through Sale letter or registered deed , this flat area shall be compulsorily recorded in metric units only . ( Square meters )
These four examples are adequate to explain why the construction person needs to have a working knowledge about both the systems.
In case you wish to know further about the history of these English and Metric measurement systems
right from the ancient times to the Metrication of the units , the following links shall certainly take you much further :