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INDUSTRIALRING ROAD PROJECT

Contract C1 & C2

Stay Cablesand Bridge

Deck Installation

Dr.Padipat ChaemmangkangVSL (Thailand) Co., Ltd.

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CONTRACT NO.2

CONTRACT NO.1 CONTRACT NO.3

NorthMain Bridge

SouthMain Bridge

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CONTRACTS C1 & C2

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BASIC INFORMATIONOF THE BRIDGES

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South Main Bridge (Contract C1)

Span main span length 398mno. of segments 2x16 + 1

Alignment gradient max. 3.5%radius in plan straightcrossfall (reversed V-shaped) constant ±2.5%

Segment width 35.9m depth 2.7-3.2mlength/weight connect’n box 7.0m/311t

unit 1 10.0m/386tunit 2-15 12.0m/431-492tclosure unit 10.0m/375t

Max. Lifting Height 61.1m

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North Main Bridge (Contract C2)

Span main span length 326mno. of segments 2x13 + 1

Alignment gradient max. 3.5%radius in plan straightcrossfall (reversed V-shaped) constant ±2.5%

Segment width 35.9m depth 2.7-3.2mlength/weight connect’n box 4.95m/305t

unit 1 10.0m/377tunit 2-15 12.0m/426-487tclosure unit 10.0m/375t

Max. Lifting Height 53.7m

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HEAVYLIFTING

TECHNIQUE

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VSL Strand System

The main components of the system are the motive unit, the tensile member with the anchorage for the load, the hydraulic pump and its control.

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Motive Unit

The motive unit consists of a hydraulic centre hole jack and the upper and lower anchorages. The upper anchorage is attached to the jack piston.

During lifting the jack is extended, causing the individual strands of the tensile member to be gripped by the upper anchorage and thus to be moved upwards. At the start of the piston’s downward movement the strands are immediately gripped by the lower anchorage, while at the same time the upper opens. The load is thus moved in a step-by-step process.

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Motive Unit (continued)

For lowering operations, VSL motive units are equipped with an auxiliary device which automatically controls the opening and closing of the anchorages. Lifting and lowering operations can therefore be carried out with the same degree of safety and speed.

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Tensile member

The tensile member consists of 7-wire prestressing steel strands with a 15.2mm nominal diameter. This tensile member is anchored to the load by a specially designed end anchorage.

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Hydraulic Pump

The oil flow for the motive units is provided by electro-hydraulic pumps with either single or multiple outlets.

The characteristics of these pumps guarantee synchronized jack movements, even if loads are different. Built-in pressure gauges or remote pressure control devices allow stresses to be monitored at all times. The size of the pump can be chosen to suit the load to be moved. Movement speeds vary according to the project and if required can be in excess of 20m /hour.

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Control and Monitoring Systems

All VSL motive units, jacks and synchronized hydraulic pumps can be operated either manually or by remote control. When a precise coordination of lifting movements is required, specially designed, computer-based multi-point monitoring systems, which centrally control and monitor the operation up to final, precise height, can be applied.

When loads from a number of different points are centrally monitored, custom designed equipment displays the pressures digitally and graphically, and provide print-outs of the results.

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VSL SSI 2000STAY CABLE SYSTEM

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SSI 2000 SYSTEM’S FEATURES

The system has been optimized to facilitate cable installation on site. Because it uses prefabricated anchorages, there is no anchorage component assembly on the deck or the pylon along the critical bridge erection path. The very compact anchorages permit easy installation in confined locations inside deck units and pylons. Single-strand installation and stressing are standard features of the system.

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SSI 2000 SYSTEM’S FEATURES(continued)

The individual encapsulation of each strand avoids the risk of corrosion migration inside stay cable areas that cannot be visually inspected. Full individual strand encapsulation is achieved by providing each strand with its own protection tube and sealing details in the anchorages. This special sealing system ensures full protection of the strand during the construction phase. The performance of the seals can be checked at any time during the design life of the stay.

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STAY CABLE &DECK INSTALLATION

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Stay Cable Installation

The first stay cable was installed 16th November 2005 and following a tight 5 and 6-day cycle, the erection works was finalized within a record time of 4 months with the last stay cable erected 19th

March 2006.

The stay cables were installed using VSL Standard strand-by-strand installation techniques utilizing winches and were stressed by a combination of Manual and Automatic Stressing Systems.

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Stressing

Before starting the stressing process, the stressing sequences and stressing force shall be predetermined for all cables. During stressing of the stay cables, the stressing force, the deflection of the deck segments and the pylon shall be closely monitored so that the tolerances are not exceeded.

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Stressing (continued)

Essential data to be provided by the designer is as follows:

1 The construction sequence.2 Coordinate of bridge after construction.3 Tensile forces and correspondent deflections at

deck and pylon in installation stage.4 Tensile forces and correspondent deflections at

deck and pylon in each adjustment stage.5 Tensile forces and correspondent deflections at

deck and pylon for final tuning of the stays.

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General Procedure

1 Erection of cable-stayed segments2 First bridge level is recorded and checked against

the predicted theoretical level.3 Strand by strand installation of the strands in the

main span stays.4 Strand by strand installation of the strands in the

side span stays.

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General Procedure (continued)

5 Pylon and deck deflection is checked and compared by the predicted values given by the designer.

6 Erection of segment.7 Re-stressing of the stays simultaneously , e.g.

main span pylon (MSP) and side span pylon (SSP) to be stressed simultaneously with four nos. of mono-strand jack. With mono-strand jacks, stressing force is evenly applied onto strands by stressing to a pre-calculated elongation rather than force.

8 New cycle.

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Bridge Deck Installation

The composite bridge deck segments were pre-fabricated approximately 22-km down the Chao-Phraya River and transported to the site by barges. The segments were lifted from the barge to the final deck elevation using VSL Modular Self Launching Deck Erection Gantries.

Due to Chao-Phraya River being extremely busy with commercial river traffic in the vicinity of the bridges, the lifting speed of the VSL System was set such that the lifting could be completed safely in approximately two hours.

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Bridge Deck Installation (continued)

The key works of deck lifting and stay cable installation were carried out by VSL operating on a 24hours/7days schedule, where the coordination between the two disciplines resulted in an erection cycle two days faster than initially anticipated, allowing a gain of about a month in main decks erection program.

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Strand Lifting Unit SLU 330/550

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General Sequence

1 Delivery deck units to lifting location on site.2 Anchor the barge.3 Lower the SLB.4 Connect the SLB to the deck unit.5 Take up the initial tension in the strand.6 Confirm ready for lifting.7 Lift the deck unit.8 Remove the barge from site.

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General Sequence (continued)

9 Lift the deck unit to final level.10 Pull the deck unit back to close gap.11 Make final level adjustments.12 Make connection between deck units.13 Install the stay cables.14 Release load from the erection gantries (EG).15 Launch EG forward.

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Liftoff Procedure

1 The SLB is lowered to the deck unit on the barge.

2 The connection between the deck unit and the SLB is made with a typical pin connection.

3 A nominal portion of the expected load is introduced to the lifting system by building up the hydraulic pressure in the lifting system.

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Liftoff Procedure (continued)

4 Upon confirmation that all relevant parties are ready, the load in the hydraulic system is built up in incremental steps of 25%, 505, 80%, 90%, 95% and 100%.

5 After reaching 100%, the unit is lifted off from the temporary supports on the barge by approximately one stroke length of the SLU 330/550, i.e. ∼500mm.

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Lifting Operation

The lifting operation is a repetitive process of the jacks extending and retracting at the ends of each stroke.

1 The jack operations are controlled from the pump by the operator. While the jacks are extending the upper grippers will grip the strands and lift the load vertically. During the retract stage the load is held in the lower grippers mechanically while the upper gripper wedges allow the jack to reset for the next stroke.

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Lifting Operation (continued)

2 The lifting of the deck units is a repetitiveprocess2.1 The deck units will be lifted in discrete steps

of approximately 500mm2.2 There will be a pause of approximately 1

minute while the pistons reset for their nextstroke. The complete cycle time isdependent upon oil flow, which isadjustable.

2.3 The deck unit will move approximately±10mm while the load is transferred fromthe top anchor to the bottom anchor andvice versa in the reset phase of the jackingsystem.

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Closing the Gap between Deck Units

For all of the deck units there is a nominal gapbetween that of the ones that had been previouslyerected and the one being lifted into position. Thisgap varies from unit to unit as follows:

Connection box 1300mmUnits 1-15 600mmClosure unit 100mm

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Closing the Gap between Deck Units (continued)

1 Upon lifting the deck unit to the required level, the gap closure jacks are connected to the SLB by a typical pin connection. A small footbridge is required for VSL personnel to cross the gap and work on the lifted deck unit.

2 After the jacks are connected, the deck unit is pull close, and at the required spacing the deck unit is held temporarily while the bolted connection and stay cables are installed.

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Load Transfer onto Permanent Supports

After the connections have been made and all parties(TNNS, VSL and the design engineer) have agreed thatload can be transferred to the permanent supports, theload is slowly released from the jacking system.

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CONCLUSION

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END