Using rational method, rainfall intensity-duration curves and the data given in Fig. P 2.27 com- pute the diameter of the outfall sewer. The length of lines, drainage areas, and inlet times are marked in Fig. P 2.27 (a). Assume: (i) Run-off coefficient for the entire area = 0.30 (ii) Velocity of flow in sewers flowing full = 0.75 m/sec (iii) 5-year average frequency curve may be used, Fig. P 2.27 (b), (iv) Hydraulic elements for circular pipes flowing full are given in Table 2.2. Table 2.2 Hydraulic elements for a circular pipe flowing full Discharge (Ips) 400 600 690 1500 2000 2 A=0.016 km² Inlet time 5 min, A = 0.032 2 km Inlet time - 5 min m Diameter (mm) Manhole 1 120 m sewer 180 m- sewer 450 525 1050 1350 1450 BManhole 2 A=0.024 km Inlet time = 8 min (a) Watershed system Most remote point Manhole 3 Rainfall intensity, mm/hr Discharge 200 175 150 125 100 50 Slope of Pipe (m/m) 0.025 0.020 0.00055 0.001 0.001 25-year ave, frequency 10-year ave frequency 5-year ave. frequency Velocity (m/sec) [690 lps, 0.75 m/s, 1 m laid at 1 in 1800] 2.7 2.8 0.75 1.55 1.20 0510 20 30 40 50 60 70 80 90 100 110 120 Duration of rainfall, min (b) Rainfall intensity-duration curves for computation of storm water runoff Fig. P2.27 Storm water drainage project
Using rational method, rainfall intensity-duration curves and the data given in Fig. P 2.27 com- pute the diameter of the outfall sewer. The length of lines, drainage areas, and inlet times are marked in Fig. P 2.27 (a). Assume: (i) Run-off coefficient for the entire area = 0.30 (ii) Velocity of flow in sewers flowing full = 0.75 m/sec (iii) 5-year average frequency curve may be used, Fig. P 2.27 (b), (iv) Hydraulic elements for circular pipes flowing full are given in Table 2.2. Table 2.2 Hydraulic elements for a circular pipe flowing full Discharge (Ips) 400 600 690 1500 2000 2 A=0.016 km² Inlet time 5 min, A = 0.032 2 km Inlet time - 5 min m Diameter (mm) Manhole 1 120 m sewer 180 m- sewer 450 525 1050 1350 1450 BManhole 2 A=0.024 km Inlet time = 8 min (a) Watershed system Most remote point Manhole 3 Rainfall intensity, mm/hr Discharge 200 175 150 125 100 50 Slope of Pipe (m/m) 0.025 0.020 0.00055 0.001 0.001 25-year ave, frequency 10-year ave frequency 5-year ave. frequency Velocity (m/sec) [690 lps, 0.75 m/s, 1 m laid at 1 in 1800] 2.7 2.8 0.75 1.55 1.20 0510 20 30 40 50 60 70 80 90 100 110 120 Duration of rainfall, min (b) Rainfall intensity-duration curves for computation of storm water runoff Fig. P2.27 Storm water drainage project
Chapter2: Loads On Structures
Section: Chapter Questions
Problem 1P
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![Using rational method, rainfall intensity-duration curves and the data given in Fig. P 2.27 com-
pute the diameter of the outfall sewer. The length of lines, drainage areas, and inlet times are
marked in Fig. P 2.27 (a). Assume:
(i) Run-off coefficient for the entire area = 0.30
(ii) Velocity of flow in sewers flowing full = 0.75 m/sec
(iii) 5-year average frequency curve may be used, Fig. P 2.27 (b),
(iv) Hydraulic elements for circular pipes flowing full are given in Table 2.2.
Table 2.2 Hydraulic elements for a circular pipe flowing full
Discharge
(Ips)
400
600
690
1500
2000
2
A=0.016 km²
Inlet time 5 min,
A = 0.032
km
Inlet time
- 5 min
2
m
Diameter
(mm)
Manhole 1
120 m
sewer
180 m-
sewer
450
525
1050
1350
1450
BManhole 2
A=0.024 km
Inlet time = 8 min
(a) Watershed system
Most remote
point
Manhole 3
Rainfall intensity, mm/hr
Discharge
200
175
150
125
100
50
Slope of Pipe
(m/m)
0.025
0.020
0.00055
0.001
0.001
25-year ave, frequency
10-year ave frequency
5-year ave. frequency
Velocity
(m/sec)
[690 lps, 0.75 m/s, 1 m laid at 1 in 1800]
2.7
2.8
0.75
1.55
1.20
0510 20 30 40 50 60 70 80 90 100 110 120
Duration of rainfall, min
(b) Rainfall intensity-duration curves for
computation of storm water runoff
Fig. P2.27 Storm water drainage project](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F9c069166-319e-495c-a66b-7c9c93781db8%2Fbab319ee-a3c3-481c-812f-bd9b1bf434df%2Fx7p5xu_processed.jpeg&w=3840&q=75)
Transcribed Image Text:Using rational method, rainfall intensity-duration curves and the data given in Fig. P 2.27 com-
pute the diameter of the outfall sewer. The length of lines, drainage areas, and inlet times are
marked in Fig. P 2.27 (a). Assume:
(i) Run-off coefficient for the entire area = 0.30
(ii) Velocity of flow in sewers flowing full = 0.75 m/sec
(iii) 5-year average frequency curve may be used, Fig. P 2.27 (b),
(iv) Hydraulic elements for circular pipes flowing full are given in Table 2.2.
Table 2.2 Hydraulic elements for a circular pipe flowing full
Discharge
(Ips)
400
600
690
1500
2000
2
A=0.016 km²
Inlet time 5 min,
A = 0.032
km
Inlet time
- 5 min
2
m
Diameter
(mm)
Manhole 1
120 m
sewer
180 m-
sewer
450
525
1050
1350
1450
BManhole 2
A=0.024 km
Inlet time = 8 min
(a) Watershed system
Most remote
point
Manhole 3
Rainfall intensity, mm/hr
Discharge
200
175
150
125
100
50
Slope of Pipe
(m/m)
0.025
0.020
0.00055
0.001
0.001
25-year ave, frequency
10-year ave frequency
5-year ave. frequency
Velocity
(m/sec)
[690 lps, 0.75 m/s, 1 m laid at 1 in 1800]
2.7
2.8
0.75
1.55
1.20
0510 20 30 40 50 60 70 80 90 100 110 120
Duration of rainfall, min
(b) Rainfall intensity-duration curves for
computation of storm water runoff
Fig. P2.27 Storm water drainage project
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