PROJECT REPORT

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PROJECT REPORT

• DESIGN CONCEPTS OF BOW STRING GIRDER (40 M SPAN)
  OF ROAD OVERBRIDGE AND DESIGN OF SUB STRUCTURE
  FOR THE SAME.

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PRESENTED BY

• 1. R.M.MEENA
• (XEN/C/JU/NWR)
• 2. SIVA KUMAR (AXEN/Designs/MTP/MS/S.R.)
• 3. L.N.LOKHARE
• (AXEN/C/KTT/WCR)
• 4. L.B.SINGH MAURYA
• (Vice Principal/SRETC/TBM/S.R.)

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INTEGRATED COURSE BATCH NO-514

• PROJECT GUIDE
• Sri.G. Bansal
• COURSE DIRECTOR
• Sri A.K.Rai

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INTRODUCTION

• On Indian Railway there are 16471 Nos of manned
  level crossings and 19284 Nos of unmanned level
  crossings as on date. These Level crossings are
  affecting the safe effective functioning of
  Railways. The Level crossings are the accident
  prone zones and causes delay of trains due to
  detention by road traffic at gate.

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INTRODUCTION- cont

• There are loss of valuable human life and
  Railways properties due to accidents taking place
  on this level crossings. Keeping safety point of
  view it become necessary to replace these level
  crossings by ROB/RUB..

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INTRODUCTION- cont

• Replacing the level crossings with ROB/RUB are
  being done by Railways in a phased manner based
  upon its TVU. Where ever possible ROB is
  preferable over RUB due to its less maintenance,
  effective usefulness, even though the initial
  cost of ROB is more.

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SCOPE OF THE PROJECT

• The ROB comprises following different structure-
• 1. Main railway span (40 m)
• 2. Approach spans having 20 m spans
• 3. Abutment
• 4. Reinforced earth retaining wall beyond
  abutment on the approaches where height is less
  than 4.0 m

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SCOPE OF THE PROJECT - cont

• As far as super structure is concerned only
  design concept of Bow string girder is
  emphasized. However for substructure complete
  design is made and enclosed.

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ELEMENTS OF BOW STRING GIRDER

• MAIN I- GIRDER
• Main I- girder is purely a tension member because
  of its geometry. This member is proposed as a
  prestressed member .The amount the prestressing
  required shall be less since the same required
  only nullify the tension.

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ARCH MEMBER
SUSPENDERS
MAIN I GIRDER
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ARCH MEMBER

• Arch member is always in compression and hence
  RCC is sufficient to take this load. A member
  size of 450x900 at supports and 450x600 at crown
  is normally sufficient to carry the compression
  for this 40 meter span.

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SUSPENDERS

• Since suspenders are pure tension members and it
  does not requires any flexural rigidity , these
  members can be provided as HTS strands firmly
  anchored between main I beams and arch members

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CROSS GIRDER

• Cross girder can be of RCC, which spans between
  main I -girders. The spacing of cross girders is
  kept as 4.15 meter the span is 8.0 meter. At
  the top of cross girder, a continuous slab of
  span of 4.15 meter and thickness of 230 mm is
  provided. Over the slab road-wearing surface as
  per IRC, specification is provided.

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C LINE OF SPAN
L
C LINE OF BEARING
BOW STRING
L
CROSS GIRDER

4150
8m
41500
PLAN AT DECK LEVEL
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LOADING

• Live load
• Load as per IRC-6
• Combinations are
• 1. Single lane 70R wheeled/track vehicle
• 2. Two lane IRC class A, wheeled

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ADVANTAGES OF BOW STRING OVER DECK TYPE GIRDERS

• There is some considerable savings in depth of
  construction in case of bow string girder
  compared to typical deck type girder Due to
  reduced depth of construction, the over all
  length of ROB get reduced and overall economy
  achieved

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7500
ROAD SURFACE
2500
DEPTH OF CONSTRUCTION2.50m
BOX GIRDER TYPE ROB
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7500
BOW STRING GIRDER
ROAD SURFACE
2400
1000
DEPTH OF CONSTRUCTION1.0m
BOW STRING GIRDER TYPE ROB
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DESIGN CONCEPT OF BOW STRING GIRDER

• LIVE LOAD
• Like our railway bridge rules, these IRC codes
  does not provide any EUDL,so for the above
  rolling loads maximum bending moment and shear
  force shall be worked out using STAAD-PRO 2003
  software. However a manual calculation is also
  shown. Due provision for impact is also
  considered as per the code.

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DEAD LOAD

• This comprise of dead load of all element of bow
  string span ,the carriage way wearing coat, foot
  path and other miscellaneous load such as cables,
  parapets, crash barriers have been considered

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WIND LOAD

• Wind load is arrived at as per IS 875
  part-III.the wind intensity multiplied by the
  projected area gives the wind load on the
  structure.

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SUB STRUCTURE

• The substructure consists of two numbers of
  1.80 meter dia column spaced at 8.0 meter apart.
  The depth of trestle beam is fixed as 1.25 meter
  for stiffness and other practical consideration
  such as requirement during construction and
  replacement of bearing.

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8.0m
1.25m
6.525m
COLUMN 1.80m dia
1.80m
Rail level
PILE CAP
PILE 1.0m dia
ELEVATION OF SUBSTRUCTURE
4
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LOADS AND OMENTS ON COLUMN

• As we know the the column is critical at the
  pile cap level . Maximum moments will come at
  this level which are all explained through the
  following sketches. Algebraically adding all the
  moments the column section is designed

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SESMIC LOAD

• Lateral Seismic Coefficient0.04
• Importance Factor 1.5 (for important bridges)
• Foundation system factor 1.0 (for pile
  foundation)
• Design for seismic force.04x1.5x1.0.06

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SESMIC LOAD

• Code followed IRC 78
• Even though the seismic load does not affect the
  super structure, the impact on the substructure
  design is considerable.
• Seismic Zone III

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Adjoining span -20m
Bow string span- 40m
Lumped mass of super structure
Lever arm
Pile cap
1.DUE TO DEAD LOAD
Pile
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Adjoining span -20m
Bow string span- 40m
Lumped mass of trestle beam
Lever arm
Pile cap
2.DUE TO DL OF SUB STRUCTURE
Pile
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Adjoining span -20m
Bow string span- 40m
y
x

Lower load
Higher load

Un balanced moment higher load y-lower load
x
Pile cap
Pile
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Adjoining span -20m
Bow string span- 40m
1.83 m

Lever arm
Pile cap
4. DUE TO LIVE LOAD
Pile
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Foundation

• The foundation system consists of four no of 1.0m
  dia pile spaced at 3.0m apart. The piles are
  proposed to be founded on hard strata, which is
  available at 25.0m depth. The piles are of bored
  cast in situ.

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Foundation

• Max. vertical Load in pile workout to be -
• under seismic condition 264 tonnes
• under normal loads 214
  tonnes
• lateral load per pile 14
  tonnes

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Foundation

• Vertical load bearing capacity of pile 320 t
• The above capacity of piles is based on soil
  capacity at site. The pile derives its capacity
  both from friction as well as end bearing.

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FOUNDATION

• Reinforcement design of pile
• The length of fixity of pile below ground level
  Le is found based on lateral modulus of
  subgrade reaction of the pile
• The moment on pile Horizontal load x Le
• Based on the moment and the vertical load on the
  pile,the reinceforcement of the pile is designed

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Pile cap
L12.5m
Le
5.318m
L22.5m
CALCULATION OF LENGTH OF FIXITY OF PILE