Construction of the Superstructure of Major Sea Crossings

Transcription

1 Construction of the Superstructure of Major Sea Crossings Matt Carter Associate Director 2 nd International Seminar on Design & Construction of Second Penang Bridge

2 2 Second Penang Bridge

3 Donghai Bridge Incheon Bridge Penang Bridge Shenzhen Western Corridor 3 Typical Sea Crossing Bridges

4 4 Long Section Scale H:V = 10:1 Maximum water depth = 10m Typical water depth = 2 to 3m

5 5 Stonecutters Bridge, Hong Kong

6 6 Second Penang Bridge, Malaysia

7 Substructure is typically around one third of the total cost Innovative design gives substantial savings Depends on ground conditions Innovations: - Construction methods - Lateral pile load tests - Articulation - Seismic isolation 7 Substructure optimization

8 Typical Superstructure

9 Quality Production line casting in a controlled environment Economy Repetitive operations, re-use of equipment Safety Minimise working at height and over water 9 Advantages of precast construction

10 Quality Cost Speed of Construction Durability Safety Environmental Impact Aesthetics 10 Design Drivers

11 Quality Cost Speed of Construction Durability Safety Environmental Impact Aesthetics 11 Design Drivers

12 Cost High elevation / deep water Low elevation / shallow water Span For given site conditions there will be an optimum economic span With current technologies in shallow seas without navigation requirements this is typically around 50m to 55m 12

13 Economic Comparison of First Penang Bridge Based on prevailing costs and available technologies in July 1977 Source: The Penang Bridge, Planning Design and Construction by Tan Sri Datuk Professor Ir. Chin Fung Kee

14 Asia s first precast segmental bridge Design & Build contract Opened 1991 Balanced cantilever segment erection Completed project next to the old Kai Tak Airport Overhead gantry weighted 400 tonnes and was 130m long 14 Kwun Tong Bypass Phase 2

15 15

16 Comparison between First and Second Penang Penang Bridge (1985) 40m PC beam and slab Second Penang Bridge (2013) 55m precast segmental box girders

17 Typical Cross Section Typically 10 16m Typically 10 16m 16m is enough for a three lane highway with full width breakdown land

18 Precast Segmental Span by Span

19 19 Span by Span Erection

20 20 Erection Sequence

21 21 Erection Gantry

22 22

23 23

24 24 Srtuctural Completion

25 Precast Segmental Balanced Cantilever

26 Span-by-span segmental needs all of the segments in a span to be simultaneously supported by the gantry Under some design conditions this could lead to a very expensive gantry: - Long spans - Tight radius curves Deep Bay Link Shorter projects may not justify investment West Tsing Yi Viaducts 26 Why balanced cantilever?

27 27 Shenzhen Western Corridor

28 Fast Track Design & Construction Feasibility Study (incl. Conceptual Design & EIA) Aug 2001 Sep 2002 Detailed Design Jul 2002 Jul 2003 Construction (Gammon-Skanska-MBEC JV) Aug 2003 Dec 2005 (28 months) Total only ~ 4 ½ years 28

29 29

30 30 Segment erection

31 Cantilever tip derricks Segment delivery by barge Segment storage Short line segment match casting 31

32 End Spans Expansion joints are needed at regular intervals which interfere with balanced cantilever erection Options - Short end spans interrupt the rhythm of the bridge - Temporary fixity of joints - Mid span hinge - SWC hybrid solution

33 33 End span erection

34 Hong Kong Zhuhai Macau Bridge HKSAR Zhuhai 43.6 km bridge over Pearl River Estuary 1st major combined bridge & tunnel sea-crossing in China reduce travel time to 0.5 hour from HK and Pearl River West Macau 34

35 Qingzhou navigation channel HKBCF HK Section Zhuhai West Artificial Island Tunnel East Artificial Island Lantau Lantau Island Island Macau 35

36 36

37 12km long highway Including 9.4km sea crossing viaduct 37 Hong Kong Section

38 38 Hong Kong Section

39 39 75m precast segmental balanced cantilever

40 Full Span Launching Method

41 41

42 Project Overview 42 Project Overview

43 43 Incheon Bridge

44 44 Full Span Launching Method

45 45 Launching gantry

46 46 Full Span Casting Factory

47 47

48 48 Pretensioning

49 49 Erection of first segment

50 Delivery of segments in deep water which is accessible by floating crane Transportation along the already erected deck by a mutli-wheeled transporter 50

51 Segment transportation is governing load 1,300 tonne segment and 950 tonne transporter unit Spread onto four girders 51

52 52 Erection equipment

53 Full Span Launching Method Contractor was experienced with the method Very long viaduct justifies investment in bespoke launching gantry to achieve very fast construction No variations in deck width, no tight radius curves in highway alignment Marine environment and availability of large capacity floating cranes Low level viaduct makes moderate span length (50m) economical

54 Comparison of Sea Crossing Construction Methods

55 Project Deck Type Procurement Method Contractor Construction Method Second Penang Bridge Incheon Bridge Precast Concrete Box Girder Shenzhen Western Corridor Design & Build Design & Build Engineers Design UEM Builders Span by span precast segmental Samsung Construction JV Full span precast launching Gammon-Skanska- MBEC Joint Venture Balanced cantilever precast segmental Status Under Construction Completed 2009 Completed 2006 Total Length 16.9 km 12.3 km 5.5 km Viaduct Length 16.5 km 9.0 km 4.7 km Width 2 x 14.0 m 2 x 15.7 m 12 x m Typical Span 55 m 50 m 75 m Typical Bridge Unit Length 330 m 250 m 590 m 55 Three sea crossings constructed in shallow water in East Asia

56 8092 segments 3 lines of 7 moulds per line (different fabricators) Storage capacity for 780 segments (2 months supply) Typical segment 1 per day 56 Second Penang Bridge Precast Yard

57 360 segments 1 mould Storage capacity for six segments (<2 weeks production) One segment every 2 days 57 Incheon Bridge Precast Yard

58 Casting yard in mainland China 1,879 segments 6 moulds Segment casting started well in advance of erection 58 Shenzhen Western Corridor

59 Project Second Penang Bridge Incheon Bridge Number of Spans Number of Gantries 4 2 Shenzhen Western Corridor 90 (Hong Kong section) 1 overhead gantry + 4 pairs of cantilever derricks Spans Per Gantry Number of Segments 8, ,879 Number of Moulds 3 x 7 = Segments Per Mould Target Cycle Time Theoretical Duration at Target Productivity days per span per gantry 2 days per span per mould 1 week per span per gantry 20 months 24 months 4.5 months 59 Three sea crossings constructed in shallow water in East Asia

60 Second Penang Bridge Design & Build contractor can tailor method Contractor had previous experience of span by span segmental Environmental impacts acceptable with a 55m span Incheon Bridge Design & Build contractor can tailor method Contractor had previous experience of full span launching Large number of spans justifies investment in bespoke gantry Shenzhen Western Corridor Very fast track project - needs multiple gantries Limited number of spans hard to justify bespoke investment Engineers design needs flexible method Environmentally sensitive mud flats needs longer spans (75m) 60 ard

61 Conclusions With constant width and gentle plan curvature a typical span length of 50m to 55m can be constructed by any one of the three methods Speed of construction depends on number of construction fronts so the cycle time for a single gantry may not dictate project duration Span by span segmental construction is a versatile method but span is limited to around 55m Span by span segmental can be significantly accelerated if required once construction team has gone through learning curve Balanced cantilever will be more economical at longer spans Full span launching will only be economical for very large projects which tends to limit the number of contractors who will adopt it Harder to accelerate full span launching

62 Emerging Trends

63 Extension of Design Life Asset Management Structural Health Monitoring Threat and Vulnerability Assessment 63 Stainless steel reinforcement

64 Thank You