Creating Solutions Together The Construction Of The Waiwera Viaduct

Transcription

1 Waiwera bridge The Construction Of The Waiwera Viaduct

2 Solving the Construction Of Waiwera Bridge Using Balanced Cantilever and Matched Precast Segmental Erection Via Overhead Gantry By David Trayner VSL Australia Pty Ltd

3 Waiwera Viaduct Part of the ALPURT B2 NZ$330m 7km extension to the motorway north of Auckland Delivered to Transit New Zealand by the Northern Gateway Alliance (NGA) NGA comprises Leighton Contractors, Fulton Hogan, Tonkin & Taylor, URS NZ, Boffa Miskell & Transit NZ Major elements of the project include: twin 300m tunnels, several small Super Ts T s & the twin precast segmental balanced cantilever 521m long bridges over the Waiwera River. Construction of the Waiwera bridge superstructures were executed by a sub alliance between NGA and VSL. The structures were built using match pre- cast segments manufactured on site, erected as balanced cantilevers via an overhead placement gantry.

4 Waiwera Viaduct is located here:

5 Waiwera Viaduct Plan

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7 Form Of Bridge Form of bridge selected for: Optimum cost solution Constraints Cost Geographical (steep ravines, river flats) Foundations (suited larger spans, high piers) Road alignment (steeper grades, entry exit levels determined by connections to other parts) Weather constraints (propensity for rain, high wind, river valley / floods) Environmental sensitivity (native scrub, aesthetics) Logistics, limited it by low level l bridge at Weranui Rd

8 Form Of Bridge Considerations Material costs (efficiency - haunched / continuous) Labour availability & costs Resource availability existing plant & personnel. Combination of standard segments plus variable depth segments Quality (precast) Safety (maximum rationalisation) Solution Balanced Cantilever, pre-cast segmental by over head gantry

9 Form Of Bridge Summary 356 match pre-cast segments (Approx 1.040Km) 16 spans (2 carriageways - 8 spans each) Highest point off existing ground level = 30.5m 9,500m 3 of concrete 1,300T of reinforcement 12,130m2 of bridge deck 480T of PT (cantilever 173t + continuity 307t) Segments were glued and initial stressed with temp PT Bars Min / Max seg wght 50T (midspan midspan), 83T (pier) Min / Max span 64.4m 4m / 76m, & 41.1m 1m (end span) Typ segment length 2.9m Variable depth 4.3m (pier) to 2.4m midspan 11.7m deck width & nominal 3% cross fall (varying)

10 Free Cantilever Method

11 Tunnel entrances at northern end of structure

12 Typical Sequence Typical Sequence Launch Truss so that FSL is on next pier (N) Place, orientate & nail pier segment (on brg) Relocate FLCB on to pier N, launch truss into segment placement position. Erect cantilever segments balanced Acid etch, Apply epoxy glue & apply closure prestress with PT bars Install permanent PT & stress Erect Closure Pour Segment & construct closure pour Install permanent continuity PT, stress & grout

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17 Gantry Operation Gantry Two parallel truss frames to support two overhead gantry winches Truss was from a project from HK. Modified from Span by Span simply supported with 46m long spans to become a BC OH Gantry Overall length of 140m made up of 15 main elements in each truss Maximum element weight of 26T Total weight of truss and all its auxiliary components is 730T Truss height of 4.0m, individual truss widths 1.6m. Underside of truss sits 7.0m above deck level End spans constructed t using span by span method

18 Gantry Operation Gantry (Continued) The original truss req d lengthening an additional 40m was added Extended truss still not long enough to launch and place on the longest spans without an intermediate step. New truss required the front support to be placed 10m in front of the pier and the rear support to be placed near midspan. This increased the loads on the deck and meant that full continuity stressing & grouting of the span was required before launching the truss It also put casting of the diaphragm and segment nailing on the critical path

19 y p Gantry Operation Gantry (Continued) The linked criticality of the gantry operation to pier segment erection was solved by erecting the pier segments in advance with a 400t crawler crane. Other challenges: Precast accuracies Duct alignment strand pushing, ducts leaking Insert locations Wet weather segmental gluing, water damage to controls

20 Pakse Gantry

21 Deep Bay Link Gantry

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23 End Span Span by SPan

24 Pier Segment Placing

25 Pier Segment Placement

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27 Pier Segment Erection By Crane

28 Pier Segment Erection By Crane

29 Segment Casting Precasting Two moulds A designated d standard d depth (2.95 to 2.4m) + C variable depth mould (4.3 to 2.95m) also used to cast the smaller segments Typ cycle 1 seg per day for stnd depth 1 to 2 days for more complex variable depth segments Complex segments had cast in situ sections diaphragm / deviators. (Gantry limitations). Each mould had rebar jigs (top & btm separate) Rebar cages moved by OH Cranes / Forklifts

30 Segment Transporter & Straddle Carrier

31 Segment Casting Pre-casting (continued) Casting yard purpose built factory built on the alignment Segments moved using the transfer carts & straddle carrier. Segment storage on the alignment 4% grade in storage area problematic for gantry cranes solved by using Straddle Carrier & segment transporter. Segment delivered to gantry using Segment Transporter. Straddle Carrier ran on a prepared road and was also used to assemble truss

32 Segment Storage & Casting Yard on Alignment

33 Casting Yard

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36 Segment Casting Pre-casting (Continued) Challenges Labour skills, motivation, accuracy, supervision Concrete 60 MPa challenging g spec for long term creep and shrink properties. High cement content Proved relatively sticky difficulties in vibration, req d high h slumps resulted in problems in concrete slumping out of web forms. Moved to high slump with accelerators but unforgiving led to removal of accelerators and a final mix with high cement content with target slump of 140mm

37 Programme Project awarded on 9 th May 2004, TCE completed Dec 2005 Site handed over Jan 2006 (7 months late) Pre-casting 1 st segment cast Jun Last cast 19 th Dec 2007, target schedule Sept 2007, best average 32 / mnth Gantry Operations Truss commissioned Jan st Segment placed Jan Last placed April 2008, target schedule Oct 2007

38 Creating ALPURT Baseline vs Actual Pier D Pier E Pier F Pier G Abutment A2 Pier B2 Abutment A1 Pier C2 Pier B1 Launch Back to Pier D Pier C1 Baseline Casting As Cast Baseline Erection As Erected Cumulative 12/06/ /07/ /08/ /09/ /10/2006 9/11/2006 9/12/2006 8/01/2007 7/02/2007 9/03/2007 8/04/2007 8/05/2007 7/06/2007 7/07/2007 6/08/2007 5/09/2007 5/10/2007 4/11/2007 4/12/2007 3/01/2008 2/02/2008 3/03/2008 2/04/2008 2/05/2008 Pier H Abutment J1&2 Week Ending

39 Acknowledgments We would like to acknowledge and thank the following for their assistance in the project and this presentation: ti Transit New Zealand, Leighton Contractors, Fulton Hogan, Tonkin & Taylor, URS NZ, Boffa Miskell The Waiwera Bridge is a graceful, efficient and cost effective structure t delivered d in challenging circumstances. The Alliance s demonstration of its ability in overcoming obstacles has been rewarded by the award of the Newmarket Viaduct in Auckland with an even more challenging and innovative solution Watch This Space.