Slab Bridge Final KPJ

8/10/2019 Slab Bridge Final KPJ

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DESIGN OFSLAB CULVERT

Dr.K.P.Jaya

Assistant Professor

Structural Engineering Division

Anna University Chennai


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A culvert is a conduit used to enclose a flowing body of water.It may be used to allow water to pass underneath a road, railway,

or embankment.

Culverts can be made of many different materials; steel, polyvinyl chloride

(PVC) and concreteare the most common.

Formerly, construction of stone culverts was common.

INTRODUCTION
http://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Roadhttp://en.wikipedia.org/wiki/Railwayhttp://en.wikipedia.org/wiki/Embankment_%28transportation%29http://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Polyvinyl_chloridehttp://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Polyvinyl_chloridehttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Embankment_%28transportation%29http://en.wikipedia.org/wiki/Railwayhttp://en.wikipedia.org/wiki/Roadhttp://en.wikipedia.org/wiki/Water


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Culvert is a cross drainage work whose length (total length between the inner

faces of dirt walls) is less than 6.0m.

In any highway or railway project, the majority of cross drainage works fall

under this category.

Hence culverts collectively are important in any project, though the cost of

individual structures may be relatively small.

INTRODUCTION


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Culverts may be classified according to function as highway or railway culvert.

The loadings and structural details of the superstructure would be different

for these two classes.

Based on the construction of the structure, they can be on the following types:

Pipe culvert

Box culvert

Stone arch culvert

Reinforced concrete slab culvert

CLASSIFICATION


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PIPE CULVERT


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PIPE CULVERT

Used as a cross drainage work on a road or railway embankment when the

discharge through the culvert is small

Concrete pipes are classified as Non Pressure pipes (NP1 to NP4) and

pressure pipes (P1P3).

Generally Reinforced Concrete non pressure pipes (NP3) are used as culverts.

The minimum diameter of of pipe for culvert is 600 mm.

1200mm for fills up to 3.5m and 1800 mm for more than 3.5m fills.


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BOX CULVERT


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BOX CULVERT

Used for spans up to about 4m

The Height of the vent rarely exceed 3m.

If the water discharges in a drain or a channel crossing a road is small,

and if the bearing capacity of the soil is low, then a box culvert is an ideal

bridge structure.

However, the construction is relatively simpler due to easier fabrication of

formwork and reinforcements and easier placing of concrete.

This type of culvert can be used both for highway and railway.


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STONE ARCH CULVERT


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SLAB CULVERT

Economical for spans up to about 8m

The thickness of the slab and hence the dead load are quite considerable a

s the span increases.

However, the construction is relatively simpler due to easier fabrication of

formwork and reinforcements and easier placing of concrete.

This type of culvert can be used both for highway and railway.


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SLAB CULVERT


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SLAB CULVERT


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SLAB CULVERT


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The components of a culvert with R.C. deck slab are the following:

Deck slab

Abutments, wing walls and approach slabs

Foundations

Kerbs and railings.

SLAB CULVERT


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DECK SLAB

The deck slab should be designed as a one-way slab to carry the dead load and

the prescribed live load with impact and still to have stresses within the

permissible limits.

For a culvert on a State Highway, the width of the bridge may be adopted as

12m to permit two-lane carriageway.

The deck slab should be designed for the worst effect of either one lane of

IRC 70R/Class AA tracked vehicle, or one lane of 70R/Class AA wheeled

vehicle, or two lanes Class A load trains.

Thus, according to the present practice, it is necessary to compute themaximum live load bending moment for three different conditions of loading, and

then adopt for design the greatest of the three values.

SLAB CULVERT

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DESIGN OF RC SLAB CULVERTS03

The deck slab for 2-lane carriagewayshould be designed for the worst

effect of

(a) one lane of IRC Class AA / 70R tracked vehicle

(b) one lane of IRC Class AA / 70R wheeled vehicle

(c) two lanes of Class A loads

In general, it is seen that Class AA wheeled vehicle will give max. bendingmoment due to live load for spans up to 4m, and Class AA tracked vehicle

for larger spans.


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LOADING ON HIGHWAY BRIDGES...

Live load Classification (Cl. 201, IRC 6):

IRC Class A: standard loading for all permanent bridges and culverts

IRC Class B: light loading for temporary bridges

IRC Class AA : heavy loading for specified areas

Bridges designed for Class AA should be checked for Class A also, as

under certain conditions, higher stresses may be obtained under Class A.

Class 70-R : heavy loading for specified areas

Where Class 70-R is specified, it shall be used in place of IRC Class AA.

Appendix 1 gives limiting loads in various bridge classes, for classifying existing

bridges (by a number equal to the highest load class the bridge can safely

withstand).


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IRC Class A & Class B

LOADING ON HIGHWAY BRIDGES...


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TYPICAL LAYOUT OF SLAB CULVERT


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Section - CC



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Sections of Abutments and Wing Walls for Slab Bridges



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DESIGNOFDECKSLAB

Step 1: Preliminary Dimensions

Carriageway

Overall width of slab at top

Width of deck seating in span direction

Length of deck seating in roadway direction

Width of kerb at top Width of kerb at bottom

Height of kerb Thickness of slabThickness of wearing coat

Skew angle

Clear Span prependicular to support

Overall span in skew direction

Effective Span


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LOADING DATA

No of Lanes

Loading Class

MATERIAL DATA

Grade of Concrete

Grade of Steel

DESIGNOFDECKSLAB

Step 2: Loading and Material Data


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Weight of Slab

Weight of Kerb

Weight of Crash Barriers

Weight of Wearing Coat

Total Load

Bending Moment due to Dead Load

DESIGNOFDECKSLAB

Step 3: Dead Load Analysis


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1.1 3.2 1.2

27 27 114 114

4.067

C.G.Line of the Loading

1. Positioning of Wheel Loads

For maximum BM, centre of span should bisect the CG o

the loading system and nearest heavy load

0.233

DESIGNOFDECKSLAB

Step 4: Live Load Analysis

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IRC Class A or B:

Impact factor fraction

= 0.5(RC bridge) or 0.545(steel bridge) for span L = 45m

= 4.5/(6+L)(RC bridge) or 9/(13.5+L)(steel bridge)for span 3m < L < 45m

DESIGNOFDECKSLAB

2. Impact Factor

As per Clause.211.1 of IRC:6-2000


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IRC Class AA or 70R:

Impact factor fraction for tracked vehicles:

= 0.25for span L = 9m,

but for RC bridges with L > 40m, 4.5/(6+L)

= 0.25 -0.15*(L-5)/4for span 5m < L < 9m

Impact factor fraction for wheeled vehicles:

= 0.25for RC bridges with span L 12m

= 0.25for steel bridges with span L 23m

DESIGNOFDECKSLAB

2. Impact Factor



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3. Calculation of Dispersion Breadth

As per Cl.305.16.2 of IRC 21:2000 (Table.1)

be= a(1-a/lo)+b1

a = distance of centre of Gravity of the concentrated load from the

nearest support

= a constant depending on b/lo

lo= effective spanb1 = breadth of concentration area of the load,

= track contact area over the road surface of the slab in a direction at

right angles to the span + twice the thickness of wearing coat

where

DESIGNOFDECKSLAB


DESIGN OF DECK SLAB


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Table (1) - Effective Width Factor ( )

[Cl.305.16.2 of IRC:21-2000]

b/lo for simply

supported slab

for continuous

slab

0.10 0.40 0.40

0.20 0.80 0.80

0.30 1.16 1.16

0.40 1.48 1.44

0.50 1.72 1.68

0.60 1.96 1.840.70 2.12 1.96

0.80 2.24 2.08

0.90 2.36 2.16

1.00 2.48 2.24

1.10 2.60 2.28

1.20 2.64 2.361.30 2.72 2.40

1.40 2.80 2.48

1.50 2.84 2.48

1.60 2.88 2.52

1.70 2.92 2.56

1.80 2.96 2.60

1.90 3.00 2.602.00 3.00 2.60

DESIGNOFDECKSLABStep 4: Live Load Analysis

DESIGN OF DECK SLAB


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4. Intensity of load per m with Impact= (Axial Load/2)*(1+Impact Factor)/beff

5. Dispersion width along span

= [(Overall Thickness)*2+B] where B - Ground Contact Depth

6. Calculation of Bending moment with the distributed load

Table.2 - Contact Area Details For Class A Loading

[Cl.305.16.3 of IRC:21-2000]

Axle load (KN)Ground contact area

B mm W mm

114 250 500

68 200 380

27 150 200

DESIGNOFDECKSLAB



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DESIGN OF DECK SLAB


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Step 1

DESIGNOFDECKSLAB

DESIGN OF DECK SLAB


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DESIGNOFDECKSLAB


DESIGN OF DECK SLAB


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DESIGNOFDECKSLAB



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DESIGN OF DECK SLAB


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DESIGNOFDECKSLAB


DESIGN OF DECK SLAB


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DESIGNOFDECKSLAB


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DESIGNOFDECKSLAB


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DESIGNOFDECKSLAB


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DESIGNOFDECKSLAB


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DESIGNOFDECKSLAB


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DESIGNOFDECKSLAB


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DESIGNOFDECKSLAB


DESIGN OF DECK SLAB


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DESIGNOFDECKSLAB

Step 5: Bending Moment Calculation


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DESIGN OF DECK SLAB


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DESIGNOFDECKSLAB

Step 5: Check for Shear

DESIGN OF DECK SLAB


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Step 6: Reinforcement Details

DESIGNOFDECKSLAB

DESIGN OF DECK SLAB


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DESIGNOFDECKSLAB

DESIGN OF DECK SLAB


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DESIGNOFDECKSLAB

DESIGN OF DECK SLAB


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DESIGNOFDECKSLAB

DESIGN OF DECK SLAB


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Step 7: Design of Kerb

DESIGNOFDECKSLAB

DESIGN OF DECK SLAB


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DESIGNOFDECKSLAB


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MODELLING

RC C S B

1


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RC CULVERTSLABBRIDGE span = 5.4m, width = 12m

Summary of Simplified Analysis results (using effective width method):

IRC Class AA - tracked vehicle: 101.5 kNm/m

IRC Class AA - wheeled vehicle: 84.5 kNm/mIRC Class A - (2 lanes): 78.8 kNm/m

Maximum Longitudinal Moment due to Live Load:

Summary of Simplified Analysis results (using effective width method):

IRC Class AA - tracked vehicle: 69.2 kN/m

IRC Class AA - wheeled vehicle: 72.2 kN/m

IRC Class A - (2 lanes): 58.8 kN/m

Maximum Shear Force due to Live Load:

MODELLINGOFRC CULVERTSLABBRIDGEINSAP2000 2


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span = 5.4m, width = 12m

plate-shell element

(300300thickness)

Longitudinal bending moments due to DL 3


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Simplified Analysis results (kNm/m):

1) at centre: 43.7 ; 2) at edge: 32.4

Transverse bending moments due to DL 4


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Simplified Analysis results (20%) (kNm/m):

1) at centre: 8.74 ; 2) at edge: 6.48

Twisting moments due to DL 5


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1) at centre: 0.0 ; 2) at edge: 0.0

Arrangement of IRC Class AA tracked vehicle loads 6


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Longitudinal bending moments due to LL 7


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1) at centre: 101.5 ; 2) at edge: 101.5

Transverse bending moments due to LL8


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Transverse bending moments due to LL

Simplified Analysis results (30%) (kNm/m):

1) at centre: 30.35 ; 2) at edge: 30.35

Twisting moments due to LL 9


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DEFORMED SHAPE UNDER COMBINED DL + LL10


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DEFORMEDSHAPEUNDERCOMBINEDDL + LL

Longitudinal bending moments due to DL+LL 11


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1) at centre: 145.2 ; 2) at edge: 133.9

Transverse bending moments due to DL+LL 12


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1) at centre: 39.2 ; 2) at edge: 36.9

Twisting moments due to DL+LL 13


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Twisting moment (at location of max. long. moment) 14


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16


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Reinforcementdetailing for 5.0mclear span

MOST

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Slab Bridge Final KPJ