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TRANSCRIPT
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Chapter 5 Analysis of Box Culvert, Results & Design
Chapter 5
Analysis of Box Culvert, Results & Design
5.1 Introduction
~\nalysis of Box Culvert was performed in SAP 2000. The box culvert should be
designed considering the following issues.
• It should be able to discharge the volume expected during a design flood.
• The structure of drainage culvert should be designed to be stable against the dead
, superimposed dead, live and earth pressure.
5.2 Load Cases
l'ollowing load cases are to be taken in to account( since culvert is used as underpass)
I. Vehicles at Top- No vehicles at Bottom
1.1 HA only
1.2 HA & HB only
2. No Vehicles at Top- No vehicles at Bottom
2.1 No HA or HB
3. No Vehicles at top- vehicles at bottom
3.1 HA only
3.2 HA & HB only
4. Vehicles at Top & Bottom both
4.1 HA only in top & bottom both
4.2 HA in top & bottom & HB in bottom only
4.3 HA & HB in top & bottom both
4.4 HA in top & bottom & HB in top only
31
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•
Chapter 5 Analysis of Box Culvert, Results & Design
5.3 Loads on the Box Culvert
Traction Force
tit t t t t t tt ii tiJii+ Superimposed dead load
ttttt t tt ttttttttt. Live loads
tt t t t t t t tt tt iJ tttt Weight of soil
ttttt t tt titttttttt Weightofstrl}cture
Soil pressure
E 6 fttfttfttt tt t ttttt Reaction ofsoil
Figure 5.1 : Loads on the Box Culvert
~.3.1 Loads due to soil
Hydrostatic pressure
I kpending on the level of the stream, the box culvert can be either at the road level or
nuried. If it is buried, there will be soil on all four sides. Thus the following loads will act
.lue to the soil :
• The weight of the soil between the top slab and the road level acting on the top
slab.
• The soil pressure acting on the sides of the box culvert.
• If there is soil on the top slab, the soil loads will be transferred on to the side
walls.
5.3.2 Live Loads
l ive loads are generally due to vehicles traveling on the road. Live loads are calculated
according to BS5400.
32
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......
Chapter 5 Analysis of Box Culvert, Results & Design
5.3.3. Loads on the top slab.
r op slab is loaded due to the weight of soil, super-imposed dead load of the road and live
loads due to vehicles.
5.3.4. Loads on the side walls
This consists of soil pressure and any surcharge pressure due to live loads.
5.3.5. Loads on the bottom slab
The soil below supports the box culvert. This soil is loaded due to the weight of the soil
above the box culvert, weight of the soil on the top slab, weight of the box culvert and
l1ve load on the box culvert. The average upward pressure is assumed on the bottom slab.
Jhis pressure is equal to all the loads divided by the bottom slab area.
5.3.6 Horizontal Live load due to traction
lhe structure shall be designed to resist the traction forces. Traction force shall be
applied perpendicular to the walls of the box culvert. Traction force was calculated as in
accordance with section 6.6 of BS5400 Part 2.
5.3.7. Hydrostatic Pressure
lhe effect of hydrostatic pressure must be taken in to account in the design of box
culverts. (either the selected structure is vehicular culvert). Because due to heavy rain if
water table increases to the high flood level in that area it will automatically generate
high hydrostatic pressure.
33
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;__"\lapter 5 Ana\ysis of Box Cu\vert, Results & Design
5.4 Modeling of Box Culvert
\nalysis of box culvert was performed using 20 shell elements of appropriate thickness.
'lnil was modeled as springs. Then the support conditions are taken as simply supported
tt its two ends.
)epending on the SPTN values of each soil type spring constants are calculated and
· abulated below.
Depth (measured from the culvert Spring Constants
top level) (in mm)
2675 8,000
2140 16,000
Below 2140 24,000
.;;,A.l Load Calculation
'.-tl.l Dead Load Calculation
>ead load may be calculated from SAP2000 finite element software automatically .
. .;;,A.l.2. Live load calculation
IIA. Loading
I DL shall be taken as 30kN per linear meter of notional lane.
IIA loading for the Top Slab
I !A loading for the Bottom Slab
30kN/m
30kN/m
34
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...
hapter 5 Analysis of Box Culvert, Results & Design
HB Loading
·IB loading for the top slab
l fB loading for the bottom slab
30 units each 75kN
20 units each 50kN
<f. ~ <f. <f. axle axle illel4! axle
-·~ --
I I;
Ill -T+-- ~~ lm ·
t t·--- ---lll!it----'1~ --- r----Im I _
l . ----~--~ I T j I
-·~~---_1. • ''' - ··-- --·-· . -.
- 1.8 m 6 r---- --· + ----- -_m __ --+-- 1.~ m ..,
Figure 5.2: HB Vehicle Wheel Arrangement
;;,.t.l.3. Super Imposed Dead Load
\ ~sume 60mm surfacing
ompacted Density of Asphalt Concrete
oading from the surfacing
35
2450kg/m3
2450 X 0.06 X 5.35 X 9.81
7.72 kN/m
fJ.;;:. .:)"<,'.
·-~ .. ~ ' '
Chapter 5 Analysis of Box Culvert, Results & Design
5.4.1.4. Reaction from Soil Calculation
Load Case 1.1 Total HA load in top slab = 30 X 10.8
= 324 kN
Super imposed load top slab = 7.72 X 10.8
= 83.38 kN
Super imposed load bottom slab = 7.72 X 10.8
= 83.38 kN
Volume of concrete = {10.8 X ( 0.75 + 0.60) X 5.35} + 9 4.7 X 0.5 X 5.35 X 2)
= 103.148m3
Weight of concrete = 103.148 X 24
= 2475.55 kN
Total downward load = 324 + 83.38 + 83.38 + 2475.55
= 2966.31 kN
Reaction from soil = 274.66 kN/m ~ "'"<('. '':l/~ ' ' Load Case 1.2 . ,,
Total HA load in top slab = 30 X 10.8
= 324 kN
Total HB load in top slab = 75 X 4 X 4
= 1200 kN
Super imposed load top slab = 7.72 X 10.8
= 83.38 kN
Super imposed load bottom slab = 7.72x10.8
= 83.38 kN
Volume of concrete = {10.8 X ( 0.75 + 0.60) X 5.35} + 9 4.7 X 0.5 X 5.35 X 2)
= 103.148m3
Weight of concrete = 103.148x24
= 2475.55 kN
Total downward load = 324 + 1200 + 83.38 + 83.38 + 2475.55
36
...
-
Chapter 5
Reaction from soil
Load Case 2.1 Super imposed load top slab
Super imposed load bottom slab
Volume of concrete
Weight of concrete
Total downward load
Reaction from soil
Load Case 3.1 Total HA load in bottom slab
Super imposed load top slab
Super imposed load bottom slab
Volume of concrete
Weight of concrete
Total downward load
Reaction from soil
Analysis of Box Culvert, Results & Design
= 4166.31 kN
= 385.77 kN/m
= 7.72x10.8 = 83.38 kN
= 7.72 X 10.8 = 83.38 kN
= {10.8 X ( 0.75 + 0.60) X 5.35} + 9 4.7 X 0.5 X 5.35 X 2)
= 103. 148m3
= 103.148x24 = 2475.55 kN
= 83.38 + 83.38 + 2475.55 = 2642.31 kN
= 244.66 kN/m
= 30 X 10.8 = 324 kN
= 7.72x10.8 = 83.38 kN
= 7.72x10.8 = 83.38 kN
= {10.8 X ( 0.75 + 0.60) X 5.35} + 9 4.7 X 0.5 X 5.35 X 2)
= 103. 148m3
= 103.148 X 24 = 2475.55 kN
= 324 + 83.38 + 83.38 + 2475.55 = 2966.31 kN
= 274.66 kN/m
37
' ' ''
....
,_'hapter 5
Load Case 3.2 Total HA load in bottom slab
Total HB load in bottom slab
Super imposed load top slab
Super imposed load bottom slab
Volume of concrete
Weight of concrete
Total downward load
Reaction from soil
Load Case 4.1 Total HA load in top & bottom slab
Super imposed load top slab
Super imposed load bottom slab
Volume of concrete
Weight of concrete
Total downward load
Reaction from soil
Analysis of Box Culvert, Results & Design
= 30 X 10.8
= 324 kN
= 50 X 4 X 4
= 1200 kN
= 7.72 X 10.8
= 83.38 kN
= 7.72 X 10.8
= 83.38 kN
= {10.8 X ( 0.75 + 0.60) X 5.35} + 9 4.7 X 0.5 X 5.35 X 2)
= 1 03.148m3
= 103.148x24 = 2475.55 kN
= 324 + 1200 + 83.38 + 83.38 + 2475.55 = 3766.31 kN
= 348.73 kN/m
= 30 X 10.8 X 2
= 648 kN
= 7.72 X 10.8
= 83.38 kN
= 7.72x10.8
= 83.38 kN
= {10.8 X ( 0.75 + 0.60) X 5.35} + 9 4.7 X 0.5 X 5.35 X 2)
= 103.148m3
= 103.148x24 = 2475.55 kN
= 648 + 83.38 + 83.38 + 2475.55 = 3290.30 kN
= 304.66 kN/m
38
' .
-
Chapter 5
Load Case 4.2 Total HA load in top & bottom slab
Total HB load in bottom slab
Super imposed load top slab
Super imposed load bottom slab
Volume of concrete
Weight of concrete
Total downward load
Reaction from soil
Load Case 4.3 Total HA load in top & bottom slab
Total HB load in top slab
Total HB load in bottom slab
Super imposed load top slab
Super imposed load bottom slab
Volume of concrete
Analysis of Box Culvert, Results & Design
= 30x10.8x2
= 648 kN
= 50 X 4 X 4
= 1200 kN
= 7.72 X 10.8
= 83.38 kN
= 7.72 X 10.8 = 83.38 kN
= {10.8 X ( 0.75 + 0.60) X 5.35} + 9 4.7 X 0.5 X 5.35 X 2)
= 103.148m3
= 103.148x24 = 2475.55 kN
= 648 + 1200 + 83.38 + 83.38 + 2475.55 = 4090.30 kN
= 378.73 kN/m
= 30x10.8x2
= 648 kN
= 75 X 4 X 4
= 1200 kN
= 50 X 4 X 4
= 800 kN
= 7.72 X 10.8
= 83.38 kN
= 7.72 X 10.8
= 83.38 kN
= {10.8 X ( 0.75 + 0.60) X 5.35} + 9 4.7 X 0.5 X 5.35 X 2)
= 1 03.148m 3
39
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...
_·hapter 5
Weight of concrete
Total downward load
Reaction from soil
Load Case 4.4 Total HA load in top & bottom slab
Total HB load in top slab
Super imposed load top slab
Super imposed load bottom slab
Volume of concrete
Weight of concrete
Total downward load
Reaction from soil
Analysis of Box Culvert, Results & Design
= 103.148x24 = 2475.55 kN
= 648 + 1200 + 800 + 83.38 + 83.38 + 2475.55 = 5290.33 kN
= 489.85 kN/m
= 30x10.8x2
= 648 kN
= 75 X 4 X 4
= 1200 kN
= 7.72x10_8
= 83.38 kN
= 7.72 X 10.8
= 83.38 kN
= {10.8 X ( 0.75 + 0.60) X 5.35} + 9 4.7 X 0.5 X 5.35 X 2)
= 103.148m3
= 103.148 X 24 = 2475.55 kN
= 648 + 1200 + 83.38 + 83.38 + 2475_55 = 4490.30 kN
= 415.77 kN/m
40
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•'J:"s.\ ' ' . l:
-
Chapter 5
5.-t.l.S Lateral earth pressure calculation
Take Surcharge as 1 OkN/m2
Take Unclassified Soil
y = 18 kN/m3
<p = 30 dgrees
Consider at Rest condition
k0 = ( 1 - Sin <p )
= 0.5
Over-burden at top
Over-burden at 5350mm depth
Pressure Distribution
10.0 kN/m2
5.35m
58.15 kN/m2
41
Analysis of Box Culvert, Results & Design
= 10kN/m2
10+0.5x18x = 10 + kovH = 5.35
= 58.15 kN/m2
-
Chapter 5 Analysis of Box Culvert, Results & Design
5.4.1.6. Traction force
BS5400 Part 2 Section 6.6 states that
For HA loading: Traction force= 8 x 10.8 +200 (but minimum 700kN)
Traction force from HA vehicle = 286.4 kN
For HB loading
Traction force for 30units of HB vehicle
Traction force for 20units of HB vehicle
= 75 X 25% X 8 = 150 kN
=50 X 25% X 8 = 100 kN
From the above calculations Traction force for HA vehicle> HB vehicle
Apply traction force of286.4kN from HA vehicle at the center of the notional lane.
5.-t.l. 7. Hydrostatic Pressure
Take the high flood level at the selected culvert area as 4.28m
Hydrostatic pressure = hpg = 4.28 x 1000 x I 0 I 1000 = 42.8 kN/m2
Equivalent UDL = 42.8 X 5.35 x0.5 X 42.8/42.8 = 114.49 kN/m
42
Chapter 5 Analysis of Box Culvert, Results & Design
5.5 Concrete Outline Drawing of Box Culvert
RFL LINE
r- ~
I • . . • t ~I ·.~ . " . 4" " " . . j I. •. q,....._,. :...,...,. C"7"J . • 1
2
.35-o-mmTHK. CO-RBEL APPROACH SLAB
5Dmm THK : BUNOING CONCRETE ~ lii
~
4 ~ " ~ ~~'
L I - SCREED CONCRETE 15/stS __j 10800
Figure 5.3 :Concrete Outline of Box Culvert
5.6. SAP2000 model of the Box Culvert
'\ I .. " ->~- ~ '
I ~ -""
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Figure 5.4: Model of Box Culvert
43
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....
Chapter 5 Analysis of Box Culvert, Results & Design
5.7 Load Combinations
HA Only
Dead Weight = 1.15
Earth Pressure = 1.5
Superimposed Dead = 1.75
Live Load = 1.5
HAandHB
Dead Weight = 1.15
Earth Pressure = 1.5
Superimposed Dead = 1.75
Live Load = 1.3
5.8 Deformed Shape for Load Case 4.3
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Figure 5.5: Deformed shape of Mode I
44
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j
Chapter 5 Analysis ofBox Culvert, Results & Design
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Figure 5.6: Deformed shape for Mode 2
5.9 Results from the SAP2000 Modeling
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kNm
/m
141.
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30
388.
65
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8
Tab
le 5
.1
Re
sult
s fr
om t
he S
AP
2000
Mod
elin
g
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• •
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omen
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hear
kN
m/m
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rce
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98.9
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93.8
8 36
816
205.
24
9517
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....
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14.5
5 95
1 22
302.
96
3627
9
413.
54
1050
75
373.
54
448.
49
956
56
310
46
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8 45
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