Planing And Design of A Prestressed Over Bridge At Eranhipalam

 

Planing And Design of A Prestressed Over Bridge At Eranhipalam

Authors Name: Munna Sherin, Shifa Kadeeja, Sameera A, Thamanna K M Gaided by Proff. U C Ahammed Kutty, Neenu V Mohanan

KMCT College of Engineering for Women Kozhikode, Kerala

Abstract- In this project we are doing planning, analysis and design of prestressed over bridge. A bridge is a structure providing passage over an obstacle without closing the way beneath the obstacle. Its used to cross may be a river or a road, In other words, bridge is a structure for carrying the road traffic or other moving loads over a depression or obstruction such as channel, road or railway. Superstructure or Decking, Bearings, and Substructure are the components of bridge. Prestressing is a method for overcoming concretes natural weakness in tension. It can be used to produce beams, floors or bridges with a longer span than is practical with ordinary reinforced concrete

KeywordsKey Words: Prestressed flyover, Superstructure, Decking, Bearing, Substructure

1.INTRODUCTION

Our project deals with the design of prestressed concrete over bridge at Eranhipalam junction, Calicut with an objective of reducing traffic congestion and there by reduces the number of accidents. Flyovers are the key elements in any road network. Use pre-stressed concrete flyover is gaining popularity in bridge engineering fraternity because of its better stability, serviceability, economy, aesthetic appearance and structural efficiency

1. 1. DESIGN PHILOSOPHIES

      There are three philosophies for the design of reinforced concrete namely:

      1. Working stress method
      2. Ultimate load method
      3. Limit state method
   2. OBJECTIVE
      • Analyse need of flyover at the proposed site.
      • Designing the flyover manually.

1. 1. BRIDGE

      A bridge is a structure providing passage over an obstacle without closing the way beneath. The required passage may be for a road, a railway,pedestrians, a canal or a pipeline. The obstacle to be crossed may be a river, a road, In other words, bridge is a structure for carrying the road traffic or other moving loads over a depression or obstruction such as channel, road or railway.

      1. Components of bridge

         The bridge structure comprises of the following parts.

         • Foundation
         • Piers and Abutments
         • Substructure
         • Bearings
         • Wing walls and Returns
   2. PRESTRESS

      Prestressing is a method for overcoming concretes natural weakness in tension. It can be used to produce beams, floors or bridges with a longer span than is practical with ordinary reinforced concrete. Prestressing tendons (generally of high tensile steel cableor rods) are used to provide a clamping load which produces a compressive stress that balances the tensile stress that the concrete compression member would otherwise experience due to a bending load.

      1. Advantages of prestessed concrete

• Section remains un-cracked under service loads.
• Reduction of steel corrosion, thereby increase durability
• Full section is utilized
• Less deformation
• Suitable foruse in pressure vessels, liquid retaining structures
• Larger spans possible with pre stressing
• For the same span, less depth compared to reinforced concrete member
• Reduction in selfweight
• More economical section
• Suitable for precast construction
  1. LOCATION OF SITE
     • This project deals with the design of prestressed concrete over bridge at Eranhipalam junction, Calicut.
     • The junction is connected to 2 highways, namely NH-47 and NH 766
     • The proposed overbridge is across NH 766
  2. LOAD SPECIFICATIONS

A load is considered primary or secondary according to the part of the flyover which shall be designed. Wind loads are secondary loads in designing the main girders and primary load in designing the wind bracings.

Primary loads includes dead load, live load impact load and centrifugal forces. Secondary loads includes wind pressure, breaking force, lateral shock effect, temperature effect, frictional resistance at movable bearing, forces due to settlement of supports and effect of shrinkage and creep of concrete.

4.PLAN

5.MANUAL DESIGN

1. 1. Design Of Interior Panel Interior dimensions of interior panel Width=2m

      Length=10m

      Thickness of wearing coat=80mm Width of support=50cm

      Effective clear width of panel=2.5m Effective length of panel=10.5m Weight of slab=6.25KN

      Weight of wearing coat=1.76KN Total dead load=8.01KN/M^2 Factored dead load=12.015KN/M^2

      Here ly/lx > 2 therefore it is a one way slab. Dead load shear=15.018KN

      Loading-IRC Class AA Loading

      Short span bending moment=40.21kNm Long span bending moment=11.5kNm IRC Class A loading:

      Short span bending moment=6.54kNm Long span bending moment=1.87kNm

      Maximum short span bending moment=40.21kNm Total max short span bending moment=69.69kNm

      IRC Class AA:

      Total bending moment=85.8kNm IRC Class A loading:

      Total bending moment=21.86kNm Using M20 concrete and Fe415 steel, Mu limit=85800000

      Effective depth=200mm

      Area of steel Ast=1388.94mm2 Assuming 16 mm diameterbars, Spacing=140mm DISTRIBUTION STEEL

      Bending moment=19.96kNm Area Ast=284.98mm2

      Spacing for 10mm diameter bars=250mm

   2. Design Of Intermediate Cross Beam

A cross beam is a long thick bar of wood, metal or concrete that is placed between two walls or other structures in order to support the roof of a building.

Bending moment =226.25kNm Shear force=187kNm

Using limit state method of design For Fe 415 steel, fy =415N/mm^2 For M20 concrete, fck=20N/mm ^2 MR constant R=2.76

Computation of design bending moment and shear force Bending moment=339.3kNm

Shear force=280.5KN Computation of effective depth For a balanced section

Depth =554.43mm^2<760 Steel reinforcement

Area of steel=1132.51mm^2 Using 20mm dia bars

No.of bars=4nos

Actual area of steel=1256.63mm^2 Required moment,Mur=315.24*10^6Nmm

Ultimate moment,MUlim=637.67*10^6Nmm Mur<MUlim the design is ok

Check for shear

Vu=280.5*10^3N

Nominal shear stress=0.922N/mm^2 Permissible shear stress

Percentage of steel=0.41% From IS 456,table 19 Provide shear reinforcement Vus=149780N

Spacing for 2 legged 10mm stirrups

SV=287.77mm

Say 250mm c/c

Check for minimum steel area Sv=354.4mm>250mm

Hence safe.

Space occupied=160mm<400mm Check for deflection

Span/effective depth=20 for simply supported But,span /effective depth provided=3.2<20 Hence design is safe.

6.CONCLUSION

This project concludes the planning and design of flyover structures. This structure reduces the traffic control and enhances the driving. The structure is designed as per IRC class AA loading. This project helps to reduce traffic conjunction.

REFERENCES

[1] Amlan K. Sengupta,Journal of prestressed concrete structures. [2] B.C Punmia,R.C.C Designs

[3] IRC 18 2000, Design criteria for prestressed concrete road bridges(post-tensioned concrete)

[4] IRC 21, Code of practice for Road Bridges, Bureau of Indian Standards,New Delhi 2000

[5] IRC- 6- 1966, Standard Specification, Road ridges load and stresses,Bureau of Indian Standards ,New Delhi , 1966

[6] IS 1343-2012 , Code of practice for prestressed concrete, Bureau of Indian IS 456 , Plain and reinforced concrete ,Bureau of Indian Standards

[7] IS 6006 1983, Indian Standard specification for uncoated stress relieved strand for prestressed concrete