launching bridges in to the future cbdg annual · pdf fileevolution - incremental launching...

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Launching Bridges in tothe Future

CBDG Annual Conference26 June 2008

Simon BourneManaging Director

Use of Incremental Launching

• Deck lengths of more than 200m

• 30-70m spans, typically regular 45m spans

• Constant depth at L/h~16

• Single-cell boxes best

• Steel moulds to cast ~25m per week

• Steel launching nose

• Pushed or pulled over low-friction surfaces

• Straight cables or RC for launching

• Profiled cables for continuity

• See CBDG Current Practice Sheet No. 13 for more details

Evolution - Incremental Launching

• Sungai Sitiawan Bridge

– 650m long bridge over Sungai Sitiawan

– classic 45m spans, internal prestress

• Broadmeadow Estuary Bridge

– 310m long bridge over estuary and bird sanctuary

– 69m spans, props, RC and external prestress

• Blackwater Viaduct

– 450m long bridge over River Blackwater

– 58m spans, props, RC and external prestress

• Kincardine Bridge

– 1,190m long bridge over Firth of Forth

– 45m spans, external prestress

Classic Launching - Sungai Sitiawan

• 45m spans

• Constant 2.9m depth

• No temporary props

• 30m long steel nose

• Straight, internal cables for launching

• Profiled, internal cables for continuity

• Fully prestressed and fully compressed

Sungai Sitiawan BridgeLaunching nose

Internal launching prestress

Sungai Tebok Raja

Samalon Bridge

First Evolution of Launching - Broadmeadow

• 69m spans

• Constant 2.9m depth

• Temporary midspan props

• 25m long steel nose

• RC section only for launching - design to crack widths

• Profiled, external cables for continuity - 310m long

• Partially prestressed in service

Broadmeadow Estuary BridgeTemporary props and nose

External continuity cables

and deviators

at third points

External continuity cables

Broadmeadow Estuary Bridge

Broadmeadow Estuary Bridge

Second Evolution of Launching - Blackwater

• 58m spans

• Constant 2.9m depth

• Temporary midspan props

• 20m long steel nose

• RC section only for launching - design to crack widths

• Profiled, external cables for continuity

• 450m long, low-friction VBT cables

• Cables anchored only at the abutments

• Partially prestressed in service

Blackwater ViaductBlackwater ViaductTemporary props and nose

Temporary props and nose

External continuitycables

and deviatorsat third points

External continuitycables

Blackwater Viaduct

Third Evolution of Launching - Kincardine

• 45m spans typically

• Constant 2.8m depth over 1,190m

• No temporary props on marine 45m spans

• 35m long steel nose

• Straight, external cables for launching - 2 spans long

• Profiled, external cables for continuity - 3 spans long

• Partially prestressed and designed to 0.15-0.25mm crack widths

• Fully compressed under permanent loads

• Loads shared between prestress and rebar

Kincardine BridgeLaunching nose and single marine piers

Launching nose attachment

125m long casting area

with two skidding beams

on vertical CFA piles

1,200t pushing jacks

32,500t deck

Pier top and

soffit integration

to suit launching

GRAVEL

L A U N C H I N G

PILE / PIER MOMENTS

LAUNCH

2520151050

1.2MN

MLWL

MHWL

SOFT CLAY

GLACIALGRAVELLY CLAY

SANDSTONE

MUDSTONE

SANDSTONE

Single 3m diameter

bored piles

in rock sockets

Permanent steel casings

1% rebar in pile cage

sized under

launching

225mm slabs and 400mm webs

with Grade 60 concrete

3.5m long diaphragm unit with launching and continuity cables

C O N T I N U I T Y C A B L E

Continuity cables

and deviators

at third points

Kincardine Bridge

Fourth Evolution of Launching - Modular Bridges

• 15-50m spans

• Constant depths of 1-3m

• 2.5m long precast shells match-cast off site

• Assembled and infilled with concrete on site

• Straight, internal cables for launching

• Temporary props possible

• Steel nose

• Profiled, internal cables for continuity

• Fully prestressed

Objectives

• Serious competitor to steel-composite and precast beam schemes

• More elegant and efficient than steel-composite or precast beams

• Covers all standard highway locations

• Covers variable depths, spans and widths

• Launching technology to avoid working at height over the road

Evolution - Precast Shells

• Taney Road Bridge

– 110m main span cable-stayed bridge

– Alternative precast shell solution

– Quicker erection over road junction

– Easier stressing operations

• River Shannon Bridge

– 150m long 5-span bridge

– Alternative precast shell solution

– Quicker and easier construction

Taney Road BridgePrecast shells

Taney Road Bridge

River Shannon BridgePrecast shells

River Shannon Bridge

Key Features

• Speed of construction is the key to value

• Match-cast off site for safety, quality and speed

• Elimination of box forms – easier moulds

• Shell structure to provide the soffit form

• Internal prestressing in infill with continuous ducts to TR47

• Pre-assembly behind abutment for safety and quality

• Launched in to place for safety, ease and less traffic disruption

• Props may be used to reduce prestress

• Robust, simple, clean lines for low maintenance

CL

PRECAST EDGE UNIT

BARS - 2No 32 DIA.

TEMPORARYPRESTRESSING

PRECAST CONCRETE SHELL

INSITU INFILL CONCRETE

2 No 19/15mmLAUNCH CABLES

6 No 19/15mmPROFILE CABLES

Typical Midspan Section

Typical Construction Sequence

TEMPORARY STRESSFORM JOINTSPACK UNITS AND ALIGNLAUNCH OVER PROPS

ATTACH NOSESTRESS LAUNCH CABLESPOUR INFILL CONCRETE

TEMPORARY STRESSFORM JOINTSPACK UNITS AND ALIGN

3

2

1

TEMPORARY PIERS& FOUNDATIONS & FOUNDATIONS

TEMPORARY PIERS

Typical Construction Sequence

REMOVE PROPSSTRESS PROFILED CABLESCAST MONOLITHIC PIER TOPSREMOVE NOSE

COMPLETE LAUNCH

STRESS LAUNCH CABLESCOUPLE LAUNCH CABLESPOUR INFILL CONCRETE

6

5

4& FOUNDATIONSTEMPORARY PIERS TEMPORARY PIERS

& FOUNDATIONS

& FOUNDATIONSTEMPORARY PIERSTEMPORARY PIERS

& FOUNDATIONS

Typical Three-Span Bridge

Options for Varying Spans

-150

015

00 -

2000

INFILLIN-SITU

UNITSPRECAST

LC

MAXIMUM SECTION: SPANS 35-50m

MINIMUM SECTION: SPANS 15-25m

TYPICAL SECTION: SPANS 25-35m

LC

IN-SITUSTITCH

SPAN CABLESPROFILED

PIER CABLESPROFILED

CABLESLAUNCH

2000

- 27

5010

00

Options for Varying Widths

600020006000

400010004000

500015005000

TYPICAL DECK WIDTH: 11.5m

NARROW DECK: 9m

WIDE DECK: 14m

CL

LC

LC

NO

. OF

BE

AM

S

OVERALL DECK WIDTH (m)

3824

19 30

2214

9 14

64

40302010

5

4

3

2

1

Typical precast shell unit

Typical three-span bridge

Typical soffit

appearance

Typical soffit

appearance

Launching Bridges in to the Future

• High-quality concrete

• Factory-controlled conditions

• Safer and faster construction

• Minimises traffic disruption

• Integration of design and construction is key

• Low maintenance structures

• New innovations always developing

• See CBDG Current Practice Sheet 13 for more details

• See CBDG Technical Guide 12, “Guide to Modular Bridge Construction” - due out soon

WWW.BENAIMGROUP.COM

Launching Bridges in to the Future