Civil Engineering - Theory of Structures - Discussion
Discussion Forum : Theory of Structures - Section 3 (Q.No. 23)
23.
A masonry dam (density = 20, 000 N/m3) 6 m high, one metre wide at the top and 4 m wide at the base, has vertical water face. The minimum stress at the base of the dam when the reservoir is full, will be
Discussion:
9 comments Page 1 of 1.
B.Singh said:
3 years ago
Assume length is equal to 1m.
W = Density x Volume.
a=1, b=4, h=6.
W = 20000 x [1/2 x (a+b) x h x 1m],
W = 300000.
For, minimum stress = W/b (1 - 6e/b),
for stability e = b/6 = 4/6 = 0.6.
Stress = 300000/4 (1 - 6x0.6/4).
Stress 7500 N/m^2.
W = Density x Volume.
a=1, b=4, h=6.
W = 20000 x [1/2 x (a+b) x h x 1m],
W = 300000.
For, minimum stress = W/b (1 - 6e/b),
for stability e = b/6 = 4/6 = 0.6.
Stress = 300000/4 (1 - 6x0.6/4).
Stress 7500 N/m^2.
(3)
George Zac said:
1 decade ago
The correct answer is option D.
6 * (4+1)/2 * 20,000 = 300,000 N
300,000 N / 4 *1 = 75,000 N/m2
6 * (4+1)/2 * 20,000 = 300,000 N
300,000 N / 4 *1 = 75,000 N/m2
Vishu said:
9 years ago
@George Zac.
Please explain why you divided it by 4 * 1?
Please explain why you divided it by 4 * 1?
Songeta said:
9 years ago
It was first multiplied by 4 * 1 to get the value in N then again divide by the width of base 4 to get the value in N/mm2.
Mughal saltanat said:
9 years ago
Firstly, you have to take an assumption that length of dam is 1m,
Then the answer is correct only for empty dam condition.
If full reservoir condition has to be taken into account then due to moment factor value will be lesser.
In that case, the answer will be 75000-135000 = - 60KN i.e tension will be at heel.
Hope it is useful.
Then the answer is correct only for empty dam condition.
If full reservoir condition has to be taken into account then due to moment factor value will be lesser.
In that case, the answer will be 75000-135000 = - 60KN i.e tension will be at heel.
Hope it is useful.
Tanooja said:
8 years ago
Weight of the dam per unit length.
W = (a+b)/2 * H * 1 * density.
a = top width of dam,
b = bottom width of dam,
W = 3 * 10^5N.
Minimum stress=W/b(1-(6 * e)/b).
e = X-b/2.
X = moment/load,
e = 0.6.
Substitute all values.
Minimum stress = 7500N/m^2.
W = (a+b)/2 * H * 1 * density.
a = top width of dam,
b = bottom width of dam,
W = 3 * 10^5N.
Minimum stress=W/b(1-(6 * e)/b).
e = X-b/2.
X = moment/load,
e = 0.6.
Substitute all values.
Minimum stress = 7500N/m^2.
Priya said:
6 years ago
How to find X? i.e Moment load not given.
How e=0.6?
How e=0.6?
Usthad said:
6 years ago
For stability e= (b/6).
Ganesh said:
4 months ago
I think the e value is 0.666, then the minimum stress is 0.000.
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