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Hydraulic Calculation For Bridge No.:-61 Mahesana-Taranga Gauge Conversion Project

This document provides the hydraulic calculations for Bridge No. 61 on the Mahesana-Taranga Gauge Conversion Project. It includes calculations of discharge using two methods, calculation of scour depth, and a summary of key results. The discharge was calculated as 6.78 cubic meters per second using the RDSO report method and 21.47 cubic meters per second using the area velocity method. The maximum scour depth for the abutment was calculated as 1.549 meters below the high flood level. The summary lists the design discharge as 8.81 cubic meters per second, vertical clearance as 3.785 meters, and scour depth below the bed level as 0 meters.

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94 views3 pages

Hydraulic Calculation For Bridge No.:-61 Mahesana-Taranga Gauge Conversion Project

This document provides the hydraulic calculations for Bridge No. 61 on the Mahesana-Taranga Gauge Conversion Project. It includes calculations of discharge using two methods, calculation of scour depth, and a summary of key results. The discharge was calculated as 6.78 cubic meters per second using the RDSO report method and 21.47 cubic meters per second using the area velocity method. The maximum scour depth for the abutment was calculated as 1.549 meters below the high flood level. The summary lists the design discharge as 8.81 cubic meters per second, vertical clearance as 3.785 meters, and scour depth below the bed level as 0 meters.

Uploaded by

Ankita
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© © All Rights Reserved
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Hydraulic Calculation for Bridge No.

:-61
MAHESANA-TARANGA GAUGE CONVERSION PROJECT

A.) Hydraulic Data

1 Bridge No. 61
2 Latitude 23°56'5.67"N
Longitude 72°40'25.01"E
3 No. of span 2 No.
4 Clear span 6.000 m
5 High Flood Level (Observed at site) HFL 194.32 m
6 Low Water Level LWL 192.255 m
7 Lowest Bed Level LBL 192.255 m
8 Dist in U/S 300 m
9 Level in U/S 192.555 m
10 Dist in D/S 350 m
11 Level in D/S 192.105 m
12 bed Slope 0.00069231
13 Cross-Section area of channel Ac 24.374 m2
14 Wetted perimeter of channel P 19.204 m
15 Rugosity Co-efficient N 0.035
16 Silt Factor f 0.68
17 Bottom of super structure 198.105
18 50 year 24 Hrs. Rainfall R50(24) 28 Cm
19 Area Reduction Factor F 0.81
20 50 year 1 Hrs. Rainfall R50(1) 106.4 mm
Length of the stream from farthest point of the catchment to the
21 L 0.4 km
bridge
22 Area of the Catchment A 0.32 km2
Diff of elevation of bed at farthest point of catchment and the
23 H 0.16 met
bridge.
Hydraulic Calculation for Bridge No. :-61
MAHESANA-TARANGA GAUGE CONVERSION PROJECT

B.) Discharge Calculation by RDSO report RBF-16


0.345
[L^3/H]
Time of Concentration = tc = = 0.729 hrs

C = 0.332 x (R50(24) x F)0.2 = 0.620


tc hr ratio R50(tc)/R50(24) From Graph Fig 4 = x = 0.320
1 hr ratio R50(1)/R50(24) From Graph Fig 4 = y = 0.380

x R50(tc) = k x R50(1) = 89.6 mm


Coefficient K = = 0.842
y
I50=R50(tc)/tc = 122.913 mm/hr
Q50=0.278*C*I50*A = 6.78 met3/sec

C.) Discharge Calculation by Area Velocity Method

Heighest flood Level = 194.32


2
Wetted Area = 24.37 met
Wetted Perimeter = 19.20 met
Increase Height = 0 met
Linear water way = 12.00 met

Ac 24.37
Hydraulic Mean Depth = R = = = 1.269 met
P 19.20
Mannings's Velocity = V = (1/N) x (R ) 2/3 x (S) 1/2 = 0.881 met/sec
Discharge Q = Ac x V = 24.374 x 0.881 = 21.47 met3/sec

HFL for Design Discharge = 194.320 + 0.000 = 194.320


Hydraulic Calculation for Bridge No. :-61
MAHESANA-TARANGA GAUGE CONVERSION PROJECT

D.) Calculation for Scour Depth

Discharge for Foundation = Discharge fromr RBF-16=> 6.78 Q= 6.78 met3/sec


Design Discharge for Foundation = Qd= 1.30 x Q = 8.81 met3/sec ( Sub. Str.- Cl. - 4.4 )

Total Clear Span = 2x6 8.81


Discharge per met width = Qf = = 0.735
= 12 met 12.00

Scour Depth = =1.239 met ( Sub. Str.- Cl. - 4.6.4 ) (From H.F.L.)

Maximum Scour Depth for Abutment = DA = ( 1.25 x D ) = 1.549 met ( Sub. Str.- Cl. - 4.6.6 )
Maximum Scour Depth for Pier = DP = ( 2.0 x D ) = Not Applicable ( Sub. Str.- Cl. - 4.6.6 )
Scour depth below bed level=> 1.549- (194.32-192.255) => -0.52 met Say 0.0 m
For Abutment => Scour Depth-(HFL-Bed level)
(Return Wall,Drop wall &
Curtain Wall)
E.) Summary
1.) Design Discharge 8.81 met3/sec
2.) Vertical Clearance 3.785 met
3.) Permissible Vertical Clearance 0.600 met
4.) Scour Depth below Bed Level 0.00 met

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