DPR Bridges

8/17/2019 DPR Bridges

1/65

FEASIBILITY STUDY ANDPREPARATION OF DPR

FOR BRIDGE PROJECTS

FEASIBILITY STUDY ANDPREPARATION OF DPR

FOR BRIDGE PROJECTS

1

Ashok Kumar

Chief EngineerMinistry of Road Transport & HighwaysGovt. of India


2/65

2. STAGES IN PROJECT PREPARATION

• Pre-feasibility report – Possible locations

– Nature of crossing

– Traffic scenario

• Feasibility report (FR)

– Preliminar surve and data collection

2

– Preliminary investigations of alternative sites

– Rough cost assessment for various alternatives

– Economic viability (IRR)

– Special design requirements, if any

– Model study, if required

– Schedule of pre-construction activities

– Recommendations


3/65

• Detailed project report (DPR) – Detailed surveys and investigations on the approved

site and alignment

– Detailed design and drawings

– Realistic cost estimate

3

– en er ocumen s nc u ng o uan es anspecifications

– Work programme

– Quality assurance system

– Maintenance Manual

– Any other special requirements


4/65

3. DATA COLLECTION

• Index map, site plan and contour survey plan

• Topographical and catchment area map• Geological map

• Traffic data including pedestrian traffic likely to use the bridge•

4

– Longitudinal and cross-section of river – Catchment area characteristics - rainfall pattern and run-off

physical characteristics (slope, soil) – River/channel characteristics - river flow pattern i.e.

perennial/seasonal and river traffic, physical features – Flood data records and water levels i.e. HFL, OFL and LWL – High and low tide levels for tidal channels (HTL and LTL)

– Requirement of navigational clearance both horizontal andvertical


5/65

• Subsoil data (IRC:78)

Soil characteristics and erodibility of bed and bank

Foundation investigation by boring to ascertain data on S.B.C. and

settlement

Surface and sub-surface soil investigation for immediate approaches

Construction materials

Sources and quality

• Environmental data

5

Quality of air, water and ground soil Impact of bridge on marine life and other environmental conditions

Severity of environment w.r.t corrosion (severe/moderate)

Wind and seismic data


6/65

• Details of existing utility services and need for

relocation, if any

• Data on the existing bridges upstream and downstream

– Len th and s an arran ement

6

– Vertical clearance

– Substructure and superstructure

– Foundations and protection works – Special features, if any


7/65

4. CRITERIA FOR SITE SELECTION

• Generally dependent on road alignment up to say200m length. Beyond 200m length, bridge settingis to be decided first and road alignment will followthe same.

• S uare or skew crossin with an le of skew

7

• Defined banks and spread of water at HFL/HTL

• Proximity of existing bridge

• Requirement of bank protection

• Alignment and length of approaches

• Access to site

• Aesthetic consideration


8/65

5. ANALYSIS OF DATA AND

FIXING DESIGN PARAMETERS• Determination of HFL/LWL

• Design discharge and velocity of flow

• Linear waterway and span arrangement

8

• Horizontal and vertical clearances and freeboard inthe approaches

• Subsoil data in foundation• Floor protection works

• Flyovers & Interchanges – proper traffic circulation


9/65

6. CONSIDERATIONS FOR SPAN

ARRANGEMENT• Piers to be preferably in line with the existing bridge

piers in case of proximity to avoid concentration of flowand turbulence

• Span length depends on type of founding strata

• Cost of superstructure vis-a-vis foundation and

9

substructure• Time of construction

• Design efforts and time required

• Ease of construction

• Availability of suitable contractors

• Easy repairs and replaceability of superstructure

• Riding quality

• Aesthetics


10/65

7. TYPE OF SUPERSTRUCTURE• Simply supported, continuous or balanced cantilever for

conventional bridges

• Cable stayed and suspension bridges for long spans

• R.C.C. Solid slab for spans upto 10 metre• Voided R.C.C. slab for 10 to 20 metres span

• Simply supported R.C.C. T-beam and slab for 10 to 25 metre

10

• Simply supported precast/cast-in-situ P.S.C. girders and

R.C.C. deck slab for spans 25 to 40 metre

• Simply supported P.S.C. box girders upto about 60 metre

• Continuous P.S.C box girders or bow string girders upto 120to 150 metre span built with cantilever segmental construction

method.

• Continuous arch bridges in R.C.C./P.S.C.

• Steel girders with composite R.C.C. deck slab.


11/65

8. TYPE OF SUBSTRUCTURE• Solid wall type pier

• Circular column type pier (specially

11

• Solid wall type abutment

• Spill through column type abutment

• Straight/splayed return walls


12/65

9. TYPE OF FOUNDATION

• Circular well• Dumbell/Double-D shape well

12

• Pile foundation - bored pilescommonly used

• Shallow isolated open foundation

• Raft foundation


13/65

10. DECK CONFIGURATION• Two lane bridges• Multi-lane bridge with median verge and divided

carriageway• Width between outer most faces of railing kerb to

be same as the formation width in the immediate

13

• Footpath width minimum 1.50 m

• Width of median verge should preferably be kept

same as in the immediate approach• Railing in combination with crash barrier for major

bridges, flyovers, R.O.Bs

• Cross slope in deck and footpath


14/65

11. MISCELLANEOUS ITEMS• Wearing coat on bridge deck

– Concrete wearing coat not recommended due

to problem of cracking and replacement

14

– um nous concre e usua y mm cover 10 to 15 mm thick mastic asphalt water

proofing layer

– Mastic asphalt layer (25 mm thickness ormore) over 40 mm thick bituminous concrete

layer for heavy traffic condition.


15/65

• Expansion Joints - MOST Interim

Specifications & IRC: SP: 69 – 2005Guidelines and Specifications – Copper strip with polysulphide filling for small

gaps – Slab seal joint

– Stri seal oint u to 70 to 80mm a

15

– Modular joint for larger gaps – Compression seal

– Asphaltic plug joint (suitable for rehabilitation

projects) – Finger type joints for large movement


16/65

• Bearings

– Sliding plate bearings for spans around 15 metre

– Metallic rocker and rocker-cum-roller bearings (IRC 83-

Part I)

16

– as omer c ear ngs - ar

– POT cum PTFE bearings suitable for larger spans and

multi-directional rotation (IRC 83 – Part 3)

– Knuckle and pin bearings


17/65

• Utilities & Access for Inspection

– No water pipe line should be in contact with the bridge

components

– P&T and electric cables to be taken in duct supported by

17

– Maintenance platform around pier

– Continuous cantilever walkway at soffit level on either

side of box girder


18/65

12. DETAILED DESIGN AND DRAWINGS

• General arrangement drawing (GAD)

• Detailed design and drawings to be based on

18

relevant I.R.C./I.S. Codes

• Review of design based on site conditions

during execution particularly for foundations


19/65

13. TENDER DOCUMENTS

• General and special conditions of contract

• Technical specifications for various itemsbased on M.O.S.T. S ecifications

19

• Bill of Quantities (BOQ)

• Final drawings


20/65

14. SOME IMPORTANT ASPECTS OF

PROJECT PREPARATION FOR BRIDGES

• Subsoil investigation - Importance of different soilparameters in each location of bore holes for designand construction of well & pile foundation - At leastone bore hole in each foundation location for major

20

• Design of well foundation & pile foundation - loadtests

• Conceptualization to implementation - Step by step

approach

• Availability of land for storage of materials, labouraccommodation etc. for major projects


21/65

• Drainage, ventilation and lighting for sub-ways andunderpasses

• Safety of adjoining structures and pedestrainmovement during construction of urban flyoversetc.

• Design life of bridges 50-100 years depending

21

• Dynamic analysis and wind tunnel testing for cablestayed or suspension bridges

• Computer aided designs for speedy and accurateanalysis

• Realistic construction programme

• Special consideration for bridges in hilly areas


22/65

15. DURABILITY MEASURES IN

DESIGN AND CONSTRUCTION• Use of not too slender sections

• Increased cover to steel/cables• Control of cracking and crack width by good detailing

• Reduction in number of expansion joints and use of leak

22

proo o n s

• Water proofing of deck

• Anti-corrosive treatment to all steel reinforcement

• Good dense concrete

• Provision for future prestressing

• Fatigue testing of anchorages

• Fenders against barge impact on substructure


23/65

16. NEW MATERIALS &

CONSTRUCTION TECHNIQUESHigh performance concrete (HPC)

• Super-politicizes and retardars

• Corrosion resistant steel

• Low relaxation prestressing strands

• High capacity strands and multi-strand pulling jack and

23

anc orages

• HDPE sheathing and synthetic grout for cables

• Precast pretensioned girders suitable for urban flyovers

• Unbonded prestressing cables for girders

• Large diameter (upto 2.5 m) bored cast-in-situ piles infoundation

• Incremental launching

• Slip form shuttering


24/65

17. CONCLUSIONA. FEASIBILITY REPORT

• Preliminary survey and data collection

• Selection of bridge site• Detailed survey and investigation and analysis of data and test results

• Proposal of span arrangements

•

24

,

• Select appropriate types of appurtenances

• Finalise GAD

B. DETAILED PROJECT REPORT

• Prepare detailed design and drawings incorporating durability measures

and review of design

• Prepare tender documents including BOQ and technical specifications

• Prepare quality assurance plan and maintenance manual


25/65

DESIGN OF SUBSTRUCTURE &

25


26/65

Bridge Components1) Superstructure

2) Substructure

3) Foundations

4) Appurtances

26

Superstructure and Substructure, No uncertainties

Foundation: Full of uncertainties: Variation to the

contract

Hence Planning, Investigation Analysis and Design

plays a major role in deciding type of foundation


27/65

Study required for design of a Bridge• Hydraulic Analysis• Subsoil Investigation• Structural Analysis

Hydraulic Analysis:-• Sitting of Bridge• Fixing of Design discharge

27

• Scour Depth• Depth of Foundation

Subsoil Investigation:-• Bearing capacities of founding level• Soil properties of embankment material

• Soil properties of bed material

Structural Analysis:-• Stress in each component should be less than the permisseb value


28/65

HYDRAULIC PARAMETRE• DESIGN DISCHARGE

BY EMPERICAL FORMULAE

By Area Velocity MethodBy Unit Hydrograph Method

Emperical Formulae

28

• DICKENS’S FORMULAQ=CM3/4Where Q = the peak run-off in cu.m/sec. And M is the catchment area in

sq.km.

C = 11-14 where the annual rainfall is 60-120 cm;= 14-19 in Madhya Pradesh32 in Western Ghats.


29/65

• Ryve’s Formula

Q = CM2/3 The formula was devised forchennai.

Where Q is run-off in cu.m./sec., andM is the catchment area in sq. km.

29

= . or areas w n m o e coas8.5 for areas between 25 and 160 km of

the coast and10.0 for limited areas near

hills.


30/65


31/65

By Area Velocity Method• V=1/nR2/3 S1/2

Where V= the velocity in m per sec.,

R = Hydraulic mean depth= A/P

31

S = slope of the bedn = the regosity coefficient


32/65

Effective Linear Waterway• W = C√Q

Where

W = Linear Waterway

32

Q = Design maximum dischargeC = 4.8


33/65

Afflux• Afflux is the height by which the natural flood level of the

river rises at any point due to constriction and/or

obstruction which may be calculated as belowh = (V2 /17.88 + 0.015) {(A/a)2 – 1}

Where

33

h = Afflux in meteresV = average velocity of the water in the river prior toconstriction in m/sec.

A = Unobstructed sectional area of the river at proposed

site in sq.m.a = Constricted area of the river at the bridge in sq.m.


34/65

Vertical Clearance above HFLDischarge in cumecs

Upto 0.3

Minimum verticalClearances in mm

150

34

Above 0.3 and upto 3Above 3 and upto 30

Above 30 and upto

300Above 300 and upto3000

Above 3000

450600

900

1200

1500


35/65

Fixing of Deck Level1) HFL + Afflux + clearance above HFL

+Depth of Super structure

35

x ng o oun at on eve• From Hydraulic consideration – Minimum

grip below Scour level = 1/3rd Maximum

Scour depth• From Bearing Capacity Point of view


36/65

Mean Depth of Scourdsm = 1.34{Db

2 /Ksf}1/3

Where

Db = The design discharge forfoundation per metre with at

effective linear waterway.K = Silt factor for a re resentative

36

sample of bed material obtainedupto the level of anticipated deepest

scour.Ksf = 1.76(dm)

1/2

Where dm is the mean diameter of bed materialMaximum Scour for pier = 2 dsmMaximum Scour for abutment = 1.27 dsm


37/65

Type of Foundations

• Shallow Foundation(open foundation)

37

,


38/65

Type of Foundation• Shallow Foundation transfers the loads

and moments from Superstructure directlyto the foundation base, without any

38

.

• Deep Foundation, the passive relief isprovided by the soil grip below the scour

level.


39/65

Open Foundation• Suited where hard / rock strata is available

at shallow depth

39


40/65

Open foundations can be adopted:

1) Best suited where rock is available closer to the bed level

span range 20m. Made continuous by deck continuity is

economical

2) Where scour is not appreciable. Good founding dataavailable is at 3m to 4m below ground level.

40

scour level means scour shall not be more than 2m.

4) Alternatively bed can be protected.

5) Cellular open foundation suitable for rocky strata.


41/65

Pile Foundations:

Traditionally adopted for flyover and creek bridges where no

scour was expected.

Why pile foundations were not adopted for river bridgesbecause:

1 ulnerable a ainst concentration of flow

41

2) At deep scour locations unsupported length turns out to be

high

3) Can be damaged by floating debris and rolling boulders


42/65

1) Precast driven piles

2) Precast bored piles

3 Cast in-situ driven iles

TYPE OF PILE FOUNDATION

42

4) Cast in-situ bored piles

5) Steel Piles


43/65

Classification of Piles:

1) Friction Piles

43

3) Friction and End Bearing Piles


44/65

Suitable Locations:1) Span range not more than 50m

2) Scour between 10m and 15m

3) Discharge per m length low – For river

bridges

44

4) For flyovers and creeks


45/65

Well Foundations

1) Suitable for location where heavy scour occurs

2) Discharge per meter length is high

3) Velocity flow is high

45

,

5) If well foundations are adopted go for larger spans


46/65

Sinking of Well Foundation

1) Sinking by grabbing

2) Using grabbing and Kent ledge

3) Blasting

46

5) Jackdown Method


47/65

Analysis of Open Foundation

1) Design combination of actions has to be chosen

2) Load to be considerer for Design• Dead load

• Live load• Snow load• Wind load

• Water current

47

• ong tu na orces cause y tract ve e ort o ve c es or y ra ng

ofvehicles and/or those caused by restraint of movement of free bearings byfriction or deformation• Buoyancy

• Earth Pressure including live load surcharge, if any

3) Live load for two lane bridge• Class A – Double lane• 70R - Wheel

• 70R – Track• Footpath live load

4) Earth Pressure


48/65

4) Earth Pressure• Active Earth Pressure• Passive Earth Pressure

- Rankine’s TheoryKa= 1-sinφ /1-sinφKp = 1/ka

- Coulomb’s TheroyKa = cos2φ /[1+√sin(φ+α )sinφ /cosφ]2

Kp = cos2φ /[1-√sin(φ+ α)sinφ /cos?]2

5) Water Current Force

48

settlements shall be within allowable limits.

80% of contact area to be ensured in case of rock under normal condition

67% of contact area to be ensured under seismic condition.

The bearing pressure on rock shall be within allowable limits.

7) Foundation has to be socketed in case of foundation resting on rock.


49/65

Analysis of Well Foundation

1) The scour level and founding level shall be fixed,based on, waterway discharge and soilcharacteristics.

2) Sizing of well shall be carried. The wells can beanalysed either following IRC 45 in case of sandy

49

.

3) The forces and moments and foundation levelincluding the side resistance to be calculated afteraccounting for Buoyancy, Tilt and Shift.


50/65

4) a) The stability of the foundation againstoverturning and sliding shall be ensured.

b) The contact area condition remains same as that ofopen foundation

c) The base pressure and the settlement should bewithin allowable limits

50

5) Passive resistance shall be ignored where the wellsare seated on rock. Hence, the well becomesgravity well.

D i f F d i


51/65

Design of Foundation

A) Open Foundation

1) Depth of Open Foundationa – In Soil - the minimum depth of open foundation shall be upto stratum

Having safe bearing capacity but not less than 2.0m below the Scour levelor the protected bed level.

b – In Rock – In hard rock, with an ultimate crushing strength of 10 MPQ – - –

51

. .

2) Thickness of footing – Thickness of footing shallnot be less than 300mm

3) Shall be designed for the moment at the face of

pier/abutment.

4) Permissible stress

–Increased by 33% for case when wind force is considered

- Increased by 50% when seismic force is considered

5) Area of tension Reinforcement should not be less than 0.15% of theX ti


52/65

X=section area.6) All faces of the footing shall be provided with a minimum steel Of 250

mm2/m in each direction.7) Spacing of bars shall not be more than 300mm.8) Base pressure – should be less than allowable bearing capacities9) Permissible

tension at base – No tension is permitted under

any combinations of roads onsoil.

- In case of rock if tension isfound at base, the base area

52

should be reduced to a size where no

tension will occur and basepressure is recalculated.

11) The shear shall be checked at effective distance away form to face ofpier.

12) The punching shear shall be checked around pier and pile at adistance of d/2.13) The crack width if required shall be checked.


53/65

B) Pile Foundation

1) Shall be designed for minimum vertical load andmaximum moment which will decide thereinforcement.

2) The maximum loaded pile with associatedmoment shall also be checked for compressivestress in concrete.

53

3) Minimum reinforcement shall be ensured.

C) Well Foundation


54/65

1) Component of well foundation

a) Cutting Edge – Steel cutting edge shall be strong40 kg/m – to facilitate Sinking of Well

b) Well Curb – Should offer the minimum resistancewhile sinking

C) Well Foundation

54

- RCC – Minimum M25 concret- Minimum reinforcement – 72 kg/cu-m.

- In case of blasting inner faces shall be protected

with steel plates with minimum thickness not lessthan 10mm.

c) Bottom Plug – Concrete shall have minimum

cement content of 330 kg/m3

& slump – 150mm


55/65

• d Well SteiningThickness h= Kd*l^1/2

h - Minimum thicknessd - External Diameter of circular well

55

l- Depth of well in m below top of wellcap

k- a constant = 0.3

4)Shift – 150mm.


56/65

4)Shift 150mm.

5)The zero shear section shall be arrived.6)The bending moment at vertical load shall

be worked out.

7)Steining of the well foundation shall bechecked for combined axial load & Bending

56

.

8)Reinforcement may be provided accordingly.

9)For rock wells, the well steining section shallbe examined at top of the kerb.

Failure of Bridges


57/65

g

Inadequate slope protection

57

Inadequate bed protection


58/65

Inadequate bed protection

58


59/65

59Inadequate bed protectionInadequate bed protection

Inadequate opening size


60/65


60



61/65


61


62/65

Inadequate

study

62


63/65

Sliding of

bearing

63


64/65

Sliding of

64

bearing


65/65

65

Documents

DPR Bridges