1. UNIT-I STANDARD SPECIFICATION FOR ROAD BRIDGE
SECTION-B
UNIT-I
STANDARD SPECIFICATION FOR ROAD BRIDGE

2. contents IRC bridge code Determination of dead loads and live loads
Wind loads
Longitudinal forces
Centrifugal forces
Horizontal forces due to water current and buoyancy effect
Earth pressure
Temp. effect

3. Deformation stresses
secondary stresses
Erection stresses
Seismic forces

4. IRC BRIDGE CODE:
The Indian roads congress has formulated standard specification and codes of practice for road bridges with a view to establish a common procedure for the design and construction of road bridges in India. The specification are collectively known as the bridge code.

5. Determination of loads

6. It is carried by bridge member consists of its own weight.
DEAD LOAD:
The dead load carried by a bridge member consists of its own weight and the portions of the weight of the superstructure and any fixed loads supported by the member.
It is carried by bridge member consists of its own weight.

8. There are 4 types of standard loadings for which road bridges are designed:
IRC class AA loading: It consists of either a tracked vehicle 700 kN or a wheeled vehicle of 400 kN. E.g.: combat tank used by army .
IRC class 70R loading: It consists of tracked vehicles of 700kN or a wheeled vehicle of total load of 1000kN . The tracked vehicle is similar to that of class AA.
IRC class A loading: It consists of a wheel load train composed of a driving vehicle and trailers of specified axle spacing and loads. This loading adopted for permanent bridges and culverts.
IRC class B loading: This loading is similar to class B loading but adopted for temporary structures.

9. WIND LOADS:
The horizontal load used in the design of a structure to account for the effects of wind.

10. Longitudinal forces:
longitudinal forces are caused in road bridges due to:
Tractive effort caused through acceleration of the driving wheels
Braking effect due to application of brakes to the wheels

11. Centrifugal forces: Centrifugal forces is given by eq.
where a road bridge is located on a curve , the effects of centrifugal forces due to movement of vehicles should be taken into account .
Centrifugal forces is given by eq.
C= (wv^2)/12.95R

12. HORIZONTAL FORCES DUE TO WATER CURRENTS:
Any part of a bridge structure which may be submerged in running water should be designed to sustain safely the horizontal pressure due to the force of the current.

13. Buoyancy effect: Buoyancy=density of fluid *vol. of object * gravity
upward forces exerted by fluids on submerged objects.
Buoyancy=density of fluid *vol. of object * gravity

14. Lets us take an example of buoyancy effect

15. This beach ball floats.
Why?

16. Because the Buoyant Force is greater than the weight of the ball.

17. Earth pressure:
 The pressure exerted on a structure, such as a wall, by the earth which it retains.
There are 3 states of lateral earth pressure:
At rest(Ko)
Active earth pressure(wall move away from soil)=Ka
Passive earth pressure(wall move into soil)=kp

18. Temperature effect:
When steel structure is not free to expand or contrast under variation of temperature, the stresses due a variation of  30 C. From local main must be considered. The coefficient of expansion for steel and concrete is If we consider unequal variation of temperature, in some structures which are not affected by equal changes, we allowed only for  15 C.
In two hinged arches and suspension bridges the equal change of temperature has an effect on the internal forces. In continuous bridges the equal change of temperature has no effect because the girders are free to expand, but the unequal change has an effect.

19. DEFORMATION STRESSES:
Deformation stresses are considered for steel bridges only. It is defined as the bending stress in any member of an open –web girder caused by the vertical deflection of the girder combined with the rigidity of the joints.

20. Stress stain curve

21. Secondary stresses:
In steel structure, secondary forces are those which caused due to eccentricity of connections, floor beam loads, cross girder, lateral wind loads, and the movement of support.

22. Erection stresses:
The stresses that are likely to be induced in member during erection should be considered in design.

23. Seismic forces: Seismic force is generated due to earthquake.
It is a natural disaster.
It is a violent shaking of earth.

24. Effect of seismic forces:

25. Unit-II culverts

26. Introduction:
A culvert is a closed conduit used to convey water from one area to another, usually from one side of a road to the other side. 

27. Classification of culverts:
RCC slab culvert
Pipe culvert
Box culvert
Stone arch culvert
Steel girder culvert for railways.

28. RCC slab culvert:

29. Pipe culvert:

30. Box culvert:

31. Stone arch culvert:

32. Steel girder culvert for railways:

33. Design of RCC slab culvert:
EXAMPLE FOR R.C. SLAB CULVERT:
GIVEN DATA
CULVERT TO BE STATE HIGHWAY.
WIDTH OF BRIDGE = (GIVEN)
NO FOOTPATH PROVIDED
condition of exposure: ’moderate’
materials: concrete grade m25
steel-deformed bars to is : 1786 (grade fe415)
clear span =given
ht. OF VENT = GIVEN
DEPTH OF FOUNDATION = GIVEN
WEARING COURSE = GIVEN
STEP-1 : DESIGN OF DECK SLAB
PRELIMINARY DIMENSIONS
DEAD LOAD BENDING MOMEMNT PER METRE WIDTH OF SLAB
LIVE LOAD BENDING MOMENT

34. STEP-2 : DESIGN BENDING MOMENT
STEP-3 : STRUCTURAL DESIGN OF DECK SLAB STEP-4 : CHECK FOR SHEAR
STEP-5: DESIGN OF KERB

35. DESIGN OF BOX CULVERT: GIVEN DATA: Clear span =given
Concrete grade M25 = 25 Mpa
Clear height = given
Steel grade Fe 415 = 415 Mpa
Top slab thickness =given
БSc (Concrete)= 8.33 Mpa
Bottom slab thickness= given
БSt (Steel) =200 Mpa
Side wall thickness=given
Modular ratio=10
Unit weight of concrete =24 kN/m3
n (for depth of neutral axis) =given
Unit weight of earth= 18 kN/m3
j (for effective depth)=given
Unit weight of water =10 kN/m3
k (for moment of resistance) =1.105 Mpa
Co-efficient of earth pressure at rest =0.5.

36. Total cushion on top 0.0m.
Thickness of wearing coat=given
load calculation
Top slab
Dead load
Live load
2. Bottom slab
Total load(DL+LL)
3.Side wall
4. Base pressure

37. Moment calculation
top slab
Bottom slab
Side wall
Distribution factor:
Moment distribution:
Braking force:
Design of section:
design moment
Top slab
Side walls
Check for shear: