Civil Engineering - GATE Exam Questions - Discussion
Discussion Forum : GATE Exam Questions - Section 6 (Q.No. 1)
1.
A prestressed concrete rectangular beam of size 300 mm x 900 mm is prestressed with an initial prestressing force of 700 kN at an eccentricity of 350 mm at midspan. Stress at top of the beam due to prestress alone, in N/mm2 is
Discussion:
14 comments Page 1 of 2.
Sameer sopori said:
7 years ago
@Vinay.
When compression increases in one side then tension will increase in another side.
Now here, we have prestressed (compressed) the bottom portion of the beam then the tension will come on the top side of the beam.
Also in bridge girders, we do post-stressing (means we are increasing compression at the bottom by stressing the steel cables and increasing the tension at the top.
but if its simple beam then obviously compression will be on top and tension at the bottom.
When compression increases in one side then tension will increase in another side.
Now here, we have prestressed (compressed) the bottom portion of the beam then the tension will come on the top side of the beam.
Also in bridge girders, we do post-stressing (means we are increasing compression at the bottom by stressing the steel cables and increasing the tension at the top.
but if its simple beam then obviously compression will be on top and tension at the bottom.
Angelica A. said:
5 years ago
8.64 (Compression).
Top Stress= - (P/A) - (Pey/I).
=-(700, 000 N /(300mm * 900mm)) - ((700,000 N * 350mm * 450mm * 12)/(300mm * 900 mm ^3)).
Top Stress= - (P/A) - (Pey/I).
=-(700, 000 N /(300mm * 900mm)) - ((700,000 N * 350mm * 450mm * 12)/(300mm * 900 mm ^3)).
Priyanka said:
8 years ago
At top stress=p/a -pey/i.
=700 * 1000/300*900 -700*1000*350*450*12/300*900^3.
= 2.59-6.049.
= 3.46.
=700 * 1000/300*900 -700*1000*350*450*12/300*900^3.
= 2.59-6.049.
= 3.46.
Vinay said:
8 years ago
The answer is 8.64 (beam at the top would be in compression).
Shantanu said:
6 years ago
D is correct.
The formula is;
Stress = p/A(1+6e/b).
The formula is;
Stress = p/A(1+6e/b).
Priyanka said:
8 years ago
According to me, the answer is 3.46.
Am I right?
Am I right?
RAKESH KUMAR said:
9 years ago
Can someone solve this with the explanation?
Prabhakar Maurya said:
4 years ago
Top stress = -3.5.
Bottom stress = +8.6.
Bottom stress = +8.6.
Sumanthnunna said:
9 years ago
My Answer for this question is 3.519.
Akshay said:
8 years ago
Answer must be 3.46 N/sq.mm.
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