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WWW.BENAIMGROUP.COM
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