Launching Bridges in to the Future CBDG Annual Conference 26 June 2008 Simon Bourne Managing Director WWW.BENAIMGROUP.COM
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 Bridge Launching 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 Bridge Temporary 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 Viaduct Blackwater Viaduct Temporary props and nose
Temporary props and nose
External continuity cables and deviators at third points
External continuity cables
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 Bridge Launching 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 LAUNCH 1.2MN MHWL MLWL SOFT CLAY GLACIAL GRAVELLY CLAY SANDSTONE L A U N C H I N G PILE / PIER MOMENTS MUDSTONE SANDSTONE 0 5 10 15 20 25 Single 3m diameter bored piles in rock sockets
1% rebar in pile cage sized under launching Permanent steel casings
225mm slabs and 400mm webs with Grade 60 concrete
3.5m long diaphragm unit with launching and continuity cables
Continuity cables and deviators at third points C O N T I N U I T Y C A B L E
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 Bridge Precast shells
Taney Road Bridge
River Shannon Bridge Precast 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
Typical Midspan Section PRECAST EDGE UNIT INSITU INFILL CONCRETE C L 2 No 19/15mm LAUNCH CABLES 6 No 19/15mm PROFILE CABLES TEMPORARY PRESTRESSING BARS - 2No 32 DIA. PRECAST CONCRETE SHELL
Typical Construction Sequence 1 PACK UNITS AND ALIGN FORM JOINTS TEMPORARY STRESS 2 POUR INFILL CONCRETE STRESS LAUNCH CABLES ATTACH NOSE 3 LAUNCH OVER PROPS PACK UNITS AND ALIGN FORM JOINTS TEMPORARY STRESS TEMPORARY PIERS & FOUNDATIONS TEMPORARY PIERS & FOUNDATIONS
Typical Construction Sequence 4 POUR INFILL CONCRETE COUPLE LAUNCH CABLES STRESS LAUNCH CABLES TEMPORARY PIERS & FOUNDATIONS TEMPORARY PIERS & FOUNDATIONS 5 COMPLETE LAUNCH TEMPORARY PIERS & FOUNDATIONS TEMPORARY PIERS & FOUNDATIONS 6 REMOVE NOSE CAST MONOLITHIC PIER TOPS STRESS PROFILED CABLES REMOVE PROPS
Typical Three-Span Bridge
Options for Varying Spans PROFILED PIER CABLES LAUNCH CABLES PROFILED SPAN CABLES MINIMUM SECTION: SPANS 15-25m LC IN-SITU STITCH IN-SITU INFILL TYPICAL SECTION: SPANS 25-35m LC PRECAST UNITS 2000-2750 1500-2000 1000-1500 MAXIMUM SECTION: SPANS 35-50m
Options for Varying Widths 4000 1000 LC 4000 5000 NARROW DECK: 9m 1500 LC 5000 NO. OF BEAMS 1 2 3 4 5 4 6 9 14 14 22 19 30 24 10 20 30 38 40 OVERALL DECK WIDTH (m) TYPICAL DECK WIDTH: 11.5m 6000 2000 C L 6000 WIDE DECK: 14m
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
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