Myllysilta The Bridge Jouko Turto 07 September 2011

Transcription

1 Myllysilta The Bridge Jouko Turto 07 September 2011

2 HISTORY OF THE BRIDGE The decision on constructing the Myllysilta Bridge was made in 1970 The technical personnel and City Board of Turku opposed the presented modern 1-opening alternative The City Council voted 34 to 18 on the type to be constructed across political party lines The bridge was selected based on its appearance It was completed in 1975 Total length: 92.7 m, clear opening: 71 m, functional width: 20 m

3 STRUCTURE OF THE BRIDGE Myllysilta is founded on eight 1,200 mm piles bored m into the bedrock

4 STRUCTURE OF THE BRIDGE, FUNCTIONAL PRINCIPLE Red rods are pressed Green rods are drawn All loads are born by the piles

5 BRIDGE REPAIRS The newly constructed bridge settled more than estimated right after the test load. A decimal error was identified in the calculations, and the ground support joint of the bridge was braced in 1977 at the designer's expense There was an ongoing dispute about the matter for years, but it never reached the court In 1987, prestressing reinforcement was added to the bridge After that, the bridge ascended and descended according to temperature and traffic. It moved approx mm.

6 MYLLYSILTA AND THE MEDIA

7 WHAT HAPPENED ON AND AFTER 6 MARCH 2010?

8 WHAT HAPPENED ON 6 MARCH 2010? At 5:45 a.m., a pedestrian called the Emergency Response Centre and reported that the bridge had sunk Myllysilta was closed from traffic The city workers measured that the middle of the bridge had sunk 912 mm on 6 March at 1:00 p.m. In the afternoon, the sinking speed was 12.5 mm/h The nearby housing co-ops prepared an evacuation plan, and access to Borenranta cellar was cut off (?) Two press conferences at 3 p.m. and 8 p.m. allowed the operative personnel to work undistracted

9 MEDIA CIRCUS

10 MEDIA CIRCUS

11 -1,393-1,393-1,393-1,394 BRIDGE SETTLEMENT MONITORING Time Sinking in the middle of the bridge (mm) Piste 8 Piste 13

12 MEASURES AFTER 6 MARCH 2010 Settlement monitoring was started at neighbouring buildings. Inclinometer pipes were installed on the bank on both sides of the river to identify any horizontal movement of landmass The foundation of the bridge and the bank area were investigated in the archives. It was identified that a potential collapse will not pose risk to neighbouring buildings as the bridge foundations are in a "box" separate from the pier All kinds of experts sent their statements to city representatives. There were dozens of suggestions on measures and repairs. The suggestions were examined to identify any useful ones; 99% of the suggestions were useless

13 OUTSIDE REPAIR SUGGESTIONS Fit the bridge on pontoons for removal Lift and remove the bridge with cranes Remove the ice and the bridge will rise Lift the middle opening by placing an additional weight at the end of the deck and relocating the front piles in place Replace the bridge with a 70 m long pontoon Convert the bridge into a single-pylon cable suspension bridge, etc.

14 OUTSIDE REPAIR SUGGESTIONS Single-pylon cable suspension bridge

15 MYLLYSILTA BRIDGE, FURTHER MEASURES On 31 March, a report on the status of the bridge found that repairing the old bridge or constructing a new bridge would cost approximately 6 8 M. On 7 April, the Board of Real Estate and Building proposed that the bridge be dismantled and replaced with a new bridge. A preliminary general drawing of a 3-opening bridge was prepared for a permit according to the Water Act. On 12 April 2010 the City Board decided to propose dismantling the bridge and replacing it with a new bridge to the City Council

16 Stages of the project plan 1. Supporting and dismantling the old bridge 1. Plan ready on 23 April 2. Direct purchasing process started on 14 April 3. Contractor selected on 12 May ( Kila jk) 2. Preliminary general drawing complete on 13 April 3. Permit procedure in accordance with Water Act (Regional State Administrative Agency for Southern Finland) 1. Application on 16 April 2. Processing time over 6 months 4. Selecting a designer and bridge type 1. Designer candidates according to framework agreement 2. 2 x 5 x pcs of general-scale plans on 2 June 3. Alternatives for steel and reinforced concrete, visual appearance, expenses, schedule 4. Decision by City Board on 15 June 5. Bridge construction planning, 20 June 15 September 6. Action permit (Building inspection) 20 June 30 July 7. Harmonising and approving plans 1 August 15 September 8. Preparing documents for contract; tender on 1 July Selecting a contractor 29 September Kilajk 10. Constructing the new bridge 15 October September 2011

17 THE DISMANTLING STARTED ON 25 MAY 2010

18 BRIDGE COMPETITION

19 BRIDGE COMPETITION

20 BRIDGE COMPETITION, WINNER: "MYLLYN TERÄS" BY WSP

21 New Myllysilta Composite girder bridge - steel girders - concrete slab Bottom of deck covered by stainless steel cladding Spans m Navigation channel in main span, width 20 m Effective deck width 20 m

22 New Myllysilta Main themes of proposal: structural reliability bridge should respect it s environment maintenance cost should be minimized

23 New Myllysilta Superstructure 4 main girders, welded I-sections Cross girders c/c 6 m steel S355K2W, Corten In-situ concrete slab Steel studs composite action between girders and slab

24 New Myllysilta Cladding Stainless steel sheets Sheets 2x4 m, thickness 4 mm Stainless steel EN /2J (brushed) Sheets supported from cross girders by secondary Z- beams Z-beams S355J2W Corten

25 New Myllysilta Substructures 2 piers on river - pile cabs - reinforced concrete column - column covered by granite stone lining - pot bearings Classic concrete abutments All supports founded on steel pipe piles filled with concrete - intermediate piers: D711 t=12,5 mm - abutments: D611 t=12,5 mm Pot bearings on all supports, longitudinally fixed on T3

26 FURTHER MEASURES Insinööritoimisto Seppo Rantala Oy was chosen as the contractor for the new bridge The construction was started on 19 October 2010 The bridge will be complete in September 2011

27 WEB CAM ON NEIGHBOURING ROOF The construction can be followed via a web cam

28 THANK YOU!