Archive for category Building Construction
Interview with Architect Javed Kachchhi | Construction Site Inspection
Posted by BenzuJK in Building Construction on December 10, 2012
What to do on a”Site Inspection/Site Visit”?
Students are always curious and nervous about site visits since this is never taught in any of the colleges in the world. Students have absolutely no idea as to what is to be done when an engineer or Architect is expected to inspect the site. By site, I mean construction site.
Check out his biography: Architect Javed Kachchhi
He is an Architect, Structural Engineer and an Interior Designer. That is the reason why I was so hung up on trying to get in touch with him and write about his experiences about site inspection.
Here we go….
My first question was…
Me: Sir, could you tell us, What exactly is “Site Inspection” or “Site Visit”?
Ar. Javed Kachchhi: Well, let me be very specific. I am sure your readers would like that.
On a site inspection, an Architect/Engineer has to take a complete survey of the site. He has to inspect each and every element that is constructed on site and make sure that the construction is being carried on as per the drawings given by the Architect.
Me: Who monitors the site?
Ar. Javed Kachchhi: Monitoring the site is the work of Site Engineers. Site Engineers have to have a degree in Civil Engineering in order to qualify for the job.
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Design of Doubly reinforced sections | Numerical example
Posted by BenzuJK in Building Construction on September 24, 2012
7 step design procedure for Doubly reinforced sections
In our article series for “Design of Doubly reinforced sections”, we covered the following:
What are doubly reinforced sections?
Methods for determining Neutral Axis?
Solved numerical examples for determining Neutral Axis
Numerical examples for practice (Find Neutral axis)
Methods for calculating Moment of Resistance
Numerical example for calculating Moment of resistance
Types of problems in Doubly reinforced sections
6 step prodecure for determining stresses in steel and concrete
Numerical example | Stresses in steel and concrete
7 step procedure for designing doubly reinforced sections
We shall now proceed with a numerical example “Design of Doubly reinforced sections” using the 7-step procedure we discussed in the previous article.
Numerical problem:
A doubly reinforced concrete beam 250mm wide and 600mm deep overall has to resist an external bending moment of 95kN-m. Find the amount of tensile and compressive steel required, if cover to the centre of steel on both sides is 50mm. σcbc = 5 N/mm2, σst = 140 N/mm2, m = 18.66
Given that:
Breadth of the beam = b = 250mm
Effective depth of the beam = d = 600 – 50 = 550mm
Distance of compressive steel from the top edge of the beam to the centre of the steel = d’ = 50mm
Permissible stress in concrete = σcbc = 5 N/mm2
Permissible stress in steel = σst = 140 N/mm2
Modular ratio = m = 18.66
Bending moment = M = 95 kN-m
Step one:
To find xc
σcbc/ (σst/m) = xc/(d – xc)
5/(140/18.66) = xc/(550 – xc)
xc = 219.95 = 220mm
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Design procedure for designing doubly reinforced section
Posted by BenzuJK in Building Construction on September 23, 2012
7 step procedure for “Design of Doubly reinforced sections”
In our article series for “Design of Doubly reinforced sections”, we covered the following:
What are doubly reinforced sections?
Methods for determining Neutral Axis?
Solved numerical examples for determining Neutral Axis
Numerical examples for practice (Find Neutral axis)
Methods for calculating Moment of Resistance
Numerical example for calculating Moment of resistance
Types of problems in Doubly reinforced sections
6 step prodecure for determining stresses in steel and concrete
Numerical example | Stresses in steel and concrete
In our previous article, we discussed a detailed 6 step procedure for determining stresses in steel and concrete followed by a numerical example. Now we shall move on with the “design procedure for doubly reinforced sections”.
Generally the following data are given:
Breadth of the beam = b
Effective depth of the beam = d
Permissible stress in concrete = σcbc
Permissible stress in steel = σst
Modular ratio = m
Bending moment = M
To solve a problem, the following procedure may be followed.
Design the beam as a singly reinforced one (balanced section)
Step One:
Find xc by
σcbc/ (σst/m) = xc/(d – xc)
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6 step procedure for determining stresses in steel and concrete | Doubly reinforced sections
Posted by BenzuJK in Building Construction on September 9, 2012
Numerical example for determining stresses in steel and concrete
In our article series for “Design of Doubly reinforced sections”, we covered the following:
What are doubly reinforced sections?
Methods for determining Neutral Axis?
Solved numerical examples for determining Neutral Axis
Numerical examples for practice (Find Neutral axis)
Methods for calculating Moment of Resistance
Numerical example for calculating Moment of resistance
Types of problems in Doubly reinforced sections
Determining stresses in steel and concrete
Numerical example | Stresses in steel and concrete
In our previous article, we discussed a detailed 6 step procedure for determining stresses in steel and concrete. Now we shall move on with a numerical example in which we will use the 6 step procedure to solve the problem.
Problem Type two: Determining stresses in steel and concrete using the 6 step procedure
A rectangular beam is 200mm wide and 480mm deep. It has to resist a bending moment of 100 kN-m. The reinforcedment consists of four 25mm ⏀ bars on tension side and three 22mm⏀bars on compression side. The centres of bars being 30mm from the top and bottom edges of the beam. Find the stresses set up in steel and concrete. m=18.66
Given data is as follows:
Breadth of the beam = b = 200mm
Effective depth of the beam = d = 480 – 30 = 450mm
Distance of compressive steel from the top edge of the beam to the centre of the steel = d’ = 30mm
Bending moment = M = 100kN-m
Modular ratio = m = 18.66
Area of tensile steel = Ast = 4 π/4 x 25 x 25 = 1964 mm2
Area of compressive steel = Asc = 4 π/4 x 22 x 22 = 1140 mm2
Step one:
Find x:
bx.x/2 + (1.5m – 1)Asc (x – d’) = mAst(d-x)
200x2/2 + (1.5×18.66 – 1) 1140 (x – 30)
= 18.66 x 1964 x (450 – x)
Therefore, x2 + 674.17x – 174147 = 0
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Determining stresses in Steel and Concrete | Doubly reinforced Sections
Posted by BenzuJK in Building Construction on September 8, 2012
Six step procedure for determining stresses in steel and concrete
In our article series for “Doubly reinforced Sections design guide”, we have covered the following:
What are doubly reinforced sections?
Methods for determining Neutral Axis?
Solved numerical examples for determining Neutral Axis
Numerical examples for practice (Find Neutral axis)
Methods for calculating Moment of Resistance
Numerical example for calculating Moment of resistance
Types of problems in Doubly reinforced sections
Determining stresses in steel and concrete
Numerical example | Stresses in steel and concrete
Now we shall proceed with a simple 6 step procedure for determining compressive stresses in steel and concrete. Further in our next article, we shall also solve a numerical using the same method.
Generally, the following data is given for reference with the help of which we can determine the stresses in steel and concrete
Breadth of the beam = b
Effective depth of the beam = d
Area of tensile steel = Ast
Area of compressive steel = Asc
Modular raito = m
Bending moment = M
Six step procedure for determining the compressive stresses in steel and concrete:
Step One:
Find x by using the following formula:
bx.x/2 + (1.5m – 1)Asc (x – d’) = mAst(d-x)
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Types of Problems | Design of Doubly Reinforced Sections
Posted by BenzuJK in Building Construction on August 7, 2012
Stepwise procedure for calculating Moment of resistance and compressive stresses in steel and concrete
While we proceed with the article series for “Doubly reinforced sections”, I would like to categorize the problems into different types. This will make your understanding of the concept better and concrete. I recommend that you practice enough to be able to understand and confidently solve the problems. This will also help you in real time when you would get into practice.
In our article series for doubly reinforced sections, we have covered the following:
What are doubly reinforced sections?
Methods for determining Neutral Axis?
Solved numerical examples for determining Neutral Axis
Numerical examples for practice (Find Neutral axis)
Methods for calculating Moment of Resistance
Numerical example for calculating Moment of resistance
Types of problems in Doubly reinforced sections
Determining stresses in steel and concrete
Numerical example | Stresses in steel and concrete
Also check out: “Singly reinforced Sections” article series.
So let’s begin with different types of problems for “Doubly reinforced sections”.
Problem type 1
To find Moment of resistance (Mr)
In a problem where we have to find Mr, specific data is given so that you could calculate the Moment of resistance. The following data will be given in the problem. I suggest that you make notes of the points below.
Breadth of the beam = b
Effective depth of the beam = d
Area of tensile steel = Ast
Area of compressive steel = Asc
Permissible stress in concrete = σcbc
Permissible stress in steel = σst
Modular ratio = m
Four – step procedure to solving the problem:
Step one:
Find xc by the following formula,
σcbc/ (σst/m) = xc/(d-xc)
Step two:
Find x using the following formula,
bxx/2 + (1.5m – 1)Asc (x – d’) = m Ast (d – x)
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Numerical Examples | Moment of Resistance Calculations
Posted by BenzuJK in Building Construction on August 1, 2012
Moment of Resistance calculations | Doubly reinforced sections
In our article series for “Doubly reinforced sections”, we have covered the following:
What are doubly reinforced sections?
Methods for determining Neutral Axis?
Solved numerical examples for determining Neutral Axis
Numerical examples for practice (Find Neutral axis)
Methods for calculating Moment of Resistance
Numerical example for calculating Moment of resistance
Types of problems in Doubly reinforced sections
Determining stresses in steel and concrete
Numerical example | Stresses in steel and concrete
Now we shall move on with a solved example. This will help you understand the methods in a better way. I suggest that you do them yourselves too. Practice will help you make your concepts more concrete and clear.
Numerical Example:
An reinforced concrete 300mm x 600mm effective dimensions is provided with tensile and compressive reinforcement of 1256mm2 each. The compressive steel is placed 30mm from the top edge of the beam. If σcbc = 7N/mm2, σst = 190N/mm2 and m = 13.33, find the moment of resistance of beam by following two methods:
1) Elastic theory method
2) Steel beam theory method
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