Phú Mỹ Bridge - MS 07 main bridge construction rev 3

main bridge construction, biện pháp thi công cầumain bridge construction, biện pháp thi công cầumain bridge construction, biện pháp thi công cầumain bridge construction, biện pháp thi công cầumain bridge construction, biện pháp thi công cầumain bridge construction, biện pháp thi công cầumain bridge construction, biện pháp thi công cầu

PHU MY BRIDGE PROJECT

METHOD STATEMENT

For CABLE-STAYED BRIDGE DECK CONSTRUCTION

Date Document No. Issue/Rev. Prepared: Reviewed: Approved:

DOCUMENT REVISION SHEET

Issue Rev Description Prepared Reviewed Approved

1 Revised Sec 1, 2, 3, 4.2, 4.4, 4.5, 4.6, 4.7, 4.8, 5, 7, 10 and Appendix 6 as marked Add Appendix 9. TP GM KF

2 Minor revisions Updated Appendices 1 and 9 Add Appendix 11. TP GM KF

3 Add Sections 4.9, 4.10, 4.11 and 4.12 Updated Section 5 TP GM KF

Appendix 1 : Deck Cycle

Appendix 2 : Deck Crane

Appendix 3 : Tower Crane

Appendix 4 : Telescopic Forklift

Appendix 5 : Casting Sequence

Appendix 6 : Survey Work Procedure

Appendix 7 : Method Statement for Post-Tensioning of Deck Tendons

Appendix 8 : Stay Cables Working Procedures (by Freyssinet)

Appendix 9 : Deck Construction Engineering Records

Appendix 10: Form Traveller Operation Manual

Appendix 11: Method Statement for Buffeting Cables (by Freyssinet)

1 GENERAL

1.1 Scope of the Method Statement

This Method Statement describes the construction of the cable stayed bridge deck This includes:

1.2 References to other Controlling Documents

The Method Statement must be read in conjunction with the following documents

• PM1-CO-MS-04 - Main Bridge Towers Construction

• PM1-CO-MS-05 - Main Bridge Pier Table Construction

• PM1-CO-MS-13 - Heavy Lifting Works

• PM1-CA-DR-14 - Main Bridge Deck Erection Manual (by LAP)

• Form Traveller Operation Manual

1.3 Specialist Subcontractors

The following specialist subcontractors will perform the services as described:

Supply and install stay cables - Freyssinet

Heavy lifting and lowering - Freyssinet

Form traveller steel fabrication - RIMP

Formwork tube steel fabrication - RIMP

1.4 Specialist Consultants

The following consultants will perform the services as described:

Permanent works design for cable stayed bridge - Arcadis

Construction Engineering and major temporary works - Cardno

2 DESCRIPTION OF THE WORKS

The cable stayed bridge deck has been designed as a cast in-situ reinforced concrete structure with an overall width of 27m The 250mm deck slab is supported by cross beams at 5m centres with longitudinal edge beams supported by stay cables at 10m centres The clearance envelope is 45m across a 250m section located at the centre span

The stay cables are in a vertical plane and are located in pods outside of the line of the edge beam Services are located beneath the deck and will pass through penetrations in the cross beams A 2.15m wide footpath cantilevers outside of the extent of the edge beam on each side The cross beam depth is 2.35m at the deck centreline from the top of concrete

The typical deck configuration consists of two vehicle lanes in each direction plus one motorcycle lane The motorcycle lanes are separated by barriers and a line of barriers along the deck centreline separates the eastbound and westbound lanes

The deck is on a vertical curve with a longitudinal grade of 5% at the towers and has a crossfall of 3% either side of centreline The drainage is via scuppers located on the kerb line outside of the edge beam The final surfacing consists of 65 mm asphaltic concrete

The deck has been designed as a cast in-situ balanced cantilever with movement joints at each tie down pier and bearings at each tower lower cross beam

3 TEMPORARY WORKS

The following main temporary works will be required for the construction of the main bridge:

• Design of form travellers

• Design of form traveller erection and lowering scheme

• Design of pier table falsework and formwork

• Design of pier table falsework and formwork erection and lowering scheme

• Design of temporary tie down cable system

• Design of buffeting cable system

• Design of closure pour (midspan and landside) clamping and formwork

arrangement

• Design of tie down pier falsework

• Design of midspan closure jacking arrangement

The construction of tower struts and the heavy lift operation are covered in PM1-CO-MS-04 and PM1-CO-MS-13, respectively

4 WORK METHODOLOGY

4.1 Construction Sequence

The basic sequence of work will be as follows:

• Construct the lower cross beam on the pile cap directly below its final position

• Erect the pier table falsework knee frames on top of the precast cross beam

• Erect the formwork system on top of the falsework

• Erect the lower cross beam for the District 7 (West) tower complete with pier table

falsework by heavy lift

• Construct the District 7 pier table

• Install the first stay cables

• Lower pier table falsework

• Erect the form travellers for the District 7 deck on each end of the pier table

• Construct the western balanced cantilever deck working away from the D7 tower

• Construct the District 2 pier table in parallel

• Cast the District 7 landside closure pour (after completion of the approach deck)

• Lower the form travellers and re erect on the District 2 pier table

• Construct the District 2 balanced cantilever deck working away from the D2 tower

• Cast the District 2 landside closure pour

• Cast the midspan closure pour

• Remove the form travellers and complete bridge furniture and deck finishes

4.2 Construction Engineering

The construction engineering will be performed by Cardno in conjunction with their specialist partner Leonhardt Andra & Partners based in Germany The Construction Engineering involves the detailed calculation of the geometry and cable forces for each stage of the construction This will be represented by a step by step analysis in which all of the theoretical loads and geometry for every stage of the construction are defined for a given construction sequence

The step by step analysis will be incorporated into a document known as the Main Bridge Deck Erection Manual (PM1-CA-DR-14) The global sequence of work for the construction of the cable stayed deck is defined in the Main Bridge Erection Manual and on the Construction Engineering drawings The Erection Manual, through reference to the step-by-step analysis, provides the detailed Construction Engineering parameters required for each stage of the construction operation This includes but is not limited to:

1 Detailed erection sequences for:

• Stay cable installation

• Installation and adjustment of temporary tie down cables

• Re-stressing of cables and cable adjustments

• Jacking operations for closure pours

2 Determination of exact forces and deflections of all parts during all erection stages This includes:

• Cable forces and cable length

• Camber values of superstructure and towers

• Support reactions

• Forces in temporary tie down cables

3 Adjustment values to account for variations in:

• Temperature conditions

• Construction live loads

• Side span closure procedures

• Main span closure procedures

It is intended that the Erection Manual will be mainly used by the Construction Engineer, the Design Manager and the Deck Engineer and as such will not be widely circulated The document will be updated with as constructed information relating geometry, forces and loads

at each stage of the construction The input and updating of the erection manual to determine the correct geometry and cable forces for each subsequent pour will be carried out by the site based construction engineer with input from the deck manager responsible for the construction

The Construction Engineer will convey information to the construction team via the Deck Engineer Information conveyed to the construction engineer such as all post pour information will be issued via the same engineer

The pro-formas for conveying this information are included in Appendix 9 of this document

4.3 Pier Table Construction

4.3.1 General

The pier table consists of the portion of bridge deck at the tower to be constructed on falsework prior to erection of the form travellers for the segmental deck This involves a central portion of 10m centrally located at the tower axis and a regular 10m segment with a pair of stay cables on either side of the central segment These three (3) segments will be cast separately in the sequence of centre, main span and side span

The pier table will be constructed in accordance with Method statement PM1-CO-MS 05

MTB Pier Table during Construction (Note the precast anchor pods and the precast cross beams)

4.4 Form Traveller

4.4.1 Design

The traveller is the travelling formwork system used for casting each deck segment Two travellers will be manufactured to facilitate the construction of one balanced cantilever at a time The travellers will then be relocated to the second tower to repeat the exercise In addition to providing a platform for the formwork, the traveller also provides sturdy access platforms enabling the completed underside of the previous segment to be accessed following launching to the following segment This enables all concrete dressing operations to be done off the critical path

The travellers are designed by Cardno with an independent check carried out by specialist partner LAP The formwork arrangement will be designed by a suitable formwork specialist and will be installed on site during the fabrication and assembly operation The hydraulic systems will be managed as a design, supply, install and commission contract Separate supply contracts or purchase orders will be issued for the rollers, sliding shoes and stress bars Platforms and ladders will be fitted on site during the assembly operation

The traveller is designed as an underslung truss assembly supported from the deck by stress bar during the setting, steel fixing and casting operations The truss assembly generally consists of a pair of longitudinal trusses connected by a transverse truss spanning between them The formwork will be supported from the forward section of the truss assembly and the access platforms will be supported from the rear The centre of gravity will be located forward

of the C-frame which means the traveller will always be front heavy Rear reaction rollers will provide stability during the raising, lowering and launching operation During casting the pivot point occurs at the C-frame position

For the launching operation the travellers will be lowered sufficiently for the formwork to clear the depth of the cross beams The lowering will be done using 40mm stress bar located at the C-frame position The traveller must be lowered perpendicular to the deck to enable the formwork to clear and thus the bars are also square to the deck

To maintain the rear reaction during lowering, raising and launching operations a pair of rear props will be provided at the rear of the traveller Contact with the underside of the deck will be made using 100 tonne capacity rollers mounted on the top of the props which roll along the soffit surface of the edge beams during the launching operation As the travellers are lowered for the stripping and launching operation each of the rear props will maintain contact with the underside of the edge beams due to the out of balance moment of the traveller To maintain the traveller parallel to the deck soffit the rear of the traveller will be raised or lowered in relation to the props via a pair of hydraulic bar jacks and stress bars with nuts located at the top of the truss and above the jacks.

The main hanger bars will be located at the C-frame position and will be pre-stressed between the top of the deck and the main block on the C-frame below the deck to ensure that no vertical movement occurs at the joint during casting The use of pre-stress also adds to the safety of the system by ensuring that the critical loads are in the structure prior to casting

During the launching operation the dead weight of the traveller is supported by two outside frames from the top of the deck which make contact with the launching beams after lowering the traveller For launching the traveller must be lowered by the depth of the cross beam to provide clearance to the formwork The raising and lowering operations will be carried out by hydraulic jacks moving a pair of steel blocks up and down the groups of stress bar on each side of the C-frame

C-The C-frame is rigidly connected at right angles to the main truss members of the traveller Due to the vertical gradient of the deck, stoppers must be fixed to the underside of the edge beam at the rear roller position prior to lowering to prevent the traveller swinging back on the stress bars

On an uphill grade, the stoppers will be located directly behind the rear prop roller On a downhill grade, the stopper will be located in front of the roller The stoppers will cause the traveller to rotate from the rear during lowering which will assist the cross beam infill formwork

to clear the beam The stoppers will be connected to the deck using removable cone anchors.The traveller will be partially supported during casting by the permanent stay cables The guide tubes will be installed into the traveller in precast concrete pods during launching The pods will be secured to the traveller by means of temporary stress bar This system enables the stay cable to be installed into the permanent anchorage prior to casting

Temporary struts will be required to carry the horizontal component of the cable force which is generated prior to placement and strength gain of the deck concrete These struts will be incorporated into the traveller and will transfer the force back to the previous anchor pod A mechanism will be provided to simplify the handling of the struts which are located on each side of the traveller

As the stay cables are located outside the line of the edge beams temporary steel support beams will be necessary to carry the full traveller weight between anchorage pods during launching The guide channels for the sliding mechanism will be located on top of these beams The beams have been designed as a box girder with lateral support legs

The traveller will be designed to be fabricated in large welded components to minimise the requirement for site welding Bolted connections will be used for site assembly where practical For transportation reasons, the C-frame will be delivered in two sections to be assembled and welded on site prior to installation The weld preparation will be done in the workshop prior to delivery by the fabricator Upon completion of the District 7 cable stayed deck, the traveller will

be lowered onto barges to be relocated onto the District 2 pier table The C-frame will be designed to hinge outwards to clear the deck during erection and dismantling of the traveller

by heavy lift

An assumed traveller weight has been used by the construction engineer for calculation of the step analysis The assumed weight has been reassessed following finalisation of fabrication of formwork and traveller components A final assessment will be made when the true weight is determined during the lifting operation by calculation from heavy lift jack pressures This weight will be conveyed to the construction engineer for assessment

4.4.2 Fabrication and Assembly

Fabrication will be carried out by a suitably qualified fabricator and the components will be shipped to site for assembly

The traveller assembly will be done on a barge adjacent to a suitable jetty at the Lotus Port using the Hitachi 200T crawler crane The components will be unloaded from the delivery vessel and transported to a position within the lifting radius of the Hitachi crane The large truss and C-frame components are likely to weigh up to 20 tonnes necessitating the use of the large crane capacity offered by the 200T crawler crane

All large components will be placed in designated positions on the Mersey river barge which measures 70m by18m Pedestals will be installed on the barge in appropriate locations to support the various traveller components during assembly The pedestals will be designed to ensure that the rear of the traveller is high enough to clear the top of the pile cap during the erection phase The rear of the traveller will overlap the side of the pile cap by approximately 5m in plan position

The form traveller access platforms will be constructed and installed upon completion of the main structural assembly Platforms will consist of mesh decking with lightweight bearers to reduce weight The structural design will ensure that the main structural elements have been designed to support all of the necessary platforms

The hydraulic system will be installed after the platforms have been completed This operation will be undertaken by the hydraulic supplier as a design, supply, install and commission package based on the jack load requirements determined by the traveller designer Cardno

The formwork will be installed following completion of the access platforms The formwork will

be designed by an experienced form designer and will be manufactured as a fabrication package combined with a proprietary shoring frame system The facing will be designed as plywood fixed to C-purlins The formwork will be assembled on site prior to installation

The basis of the operation manual will be the operational drawings contained at the back of the form traveller drawing set provided by the traveller Designer and Construction Engineer Cardno.

MTB Traveller on barge ready for erection

(Note pier table formwork in background after lowering)

MTB Traveller during Erection

(Note the C-frame arms in the hinged out position for erection and dismantling)

Panama Bridge Traveller with 45T Deck Crane.

(80T capacity is required for Phu My Bridge for pod installation)

MTB traveller in the raised/casting position

MTB Traveller in the raised/casting position(Note the rolling beam which must be moved forward following the casting

to enable the traveller to launch to the next position)

MTB Form Traveller (Note the launching beams on top of the deck above the edge beams.

Also note the precast pods installed by the deck crane during launching)

MTB form traveller launched and re-set ready for rebar installation

Sliding shoe arrangement from Panama traveller

The Phu My Bridge traveller arrangement will be similar

4.5 Deck Construction

The construction of the cable-stayed deck will be in accordance with the sequences described

in the Erection Manual which will be provided by the Construction Engineering consultant Cardno This will outline the necessary sequence for casting of each stage together with the sequence and timing for installation of temporary tie down cables and buffeting cables A summary of the content of this document is included in Section 4.2 of this document

The construction of the cable-stayed deck commences following erection of the form travellers onto the Pier Table The operation of lowering the pier table falsework is described in method statement PM1-CO-MS-13 The erection of the form travellers is also described in PM1-CO-MS-13 “Method Statement for Heavy Lifting Works”

The deck will be constructed with one segment out of balance towards the main span

4.5.1 Traveller Operation and Deck Cycle

5-day Cycle

After the initial start up period and learning curve, it is anticipated that the deck construction will proceed on a 6 day cycle reducing to a regular 5 day cycle Critical elements of the cycle will be determined by the time taken to achieve the required concrete strength nominated in drawing CS-005 of the Erection Manual A summary of the anticipated cycle together with the nominated concrete strength limitations is included in Appendix 1 of this document A flowchart

of the cycle showing the key constraints to various operations is also included in Appendix 1 for clarity.

The anticipated 5-day cycle will be as follows:

Day 1

As-built SurveyConstruction Engineering CalculationStrip stop ends & clean up

Strip stitch formsRelocate launching beams to Segment nPartial stressing of front crossbeam (to the force of 22 strands only)

Stage 2 stay cable adjustmentDestress and remove stress bars at podsDress concrete

Day 2

Release & lower longitudinal prop at podRestress front cross beam

Lower TravellerInstall and stress rear cross beam tendonAdvance traveller to accept pod (4m)Install precast cable pod during advanceComplete advance (6m further launching)Raise traveller & set Lock off

Survey traveller positionInstall precast cross beamsStress cable pod to travellerInstall prefab edge beam rebarInstall prop between podsDress concrete

Day 3

Install PT anchorages & ducts to X beamsGrout ducts in crossbeams - (Segment n-1)Install deck rebar - edge beams and wings

Day 4

Install stay cables Stage 1Complete deck rebar- central portionComplete deck rebar - wings & top of edge beamInstall stop ends

Set up for concrete Install & check all embedments + QA checks

Day 5

PourFinish & CureFlush Ducts

The cycle may be modified to better suit the production operation depending on the actual concrete strength gained as determined by testing

It is anticipated that the edge beam rebar will be pre assembled in jigs behind the leading segment enabling the deck crane to set up on the previously cast segment (segment n), lift the cage from n-1 and slew around to place the cage in segment n+1 eliminating the need for transportation of the cage The jig would then be shifted forward to the next segment at a suitable time

The details of the pod and cross beam reinforcement are described in the PM1-CO-MS-10

“Method Statement for Precast Concrete Production”

The allowable weight of rebar (excluding rebar in precast elements) which can be installed prior to stay erection is 25 tonne The total weight of the edge beam and wings represents approximately 20 tonne The total weight of the central portion of deck rebar is 10 tonne

4.5.3 Precast Concrete Elements

The production of precast concrete elements is described in detail in Method Statement for Precast Concrete Production (PM1-CO-MS-10)

The stay cable guide tubes will be precast into pod units This serves several functions:

1 It enables the geometry of the guide tubes to be accurately set in a precast bed

2 The careful work of surveying and adjusting the geometry is done off the critical

path

3 The stay cable can be installed directly into the permanent anchorage prior to

casting the deck segment This avoids the need for a temporary anchorage

system

The precast pod units are expected to weigh in the order of 20 tonnes Due to their weight the units need to be placed into the traveller during the launching operation as they will exceed the lifting capacity of the deck crane after the traveller is fully launched The weight of the pods will

be verified by carrying out a trial lift with the deck crane prior to the first erection into the traveller

The crane must be located in accordance with the sketches included in Appendix 2 of this document The fundamental requirement is for the front outriggers to be located above the front cross beam of the segment upon which the crane is located The pod must be lifted from

a position beside the crane to reduce load on the rear inside outrigger The load shall not be lifted from the rear of the crane and slewed 180 degrees as the rear outriggers are not located over a cross beam

Each cross beam will be placed into the traveller as two precast elements with a short in-situ stitch portion in the centre Each of the four (4) cross beam elements in each segment will weigh around 12 tonnes and will be installed using the deck crane set up on the deck with the front outriggers over the last cross beam, i.e., 2.2 m back from the leading edge of the deck with the traveller in the final position The crane may be located either in the centre of the deck

or at the outside position used for pod installation

4.5.4 Concrete Placement

Concrete will be placed by pump The basic pump unit will be located at the base of the tower and concrete wagons will discharge directly into the hopper The pump line will be run up the tower crane mast and along the deck in both directions A long radius 90-degree bend will be provided at deck level to enable the main vertical supply line to be connected to the appropriate deck line

A manually operated concrete distributor boom will be located in the centre of the deck at the end of the previous pour This will have a boom length of at least 12m The corners will be reached using flexible hose The horizontal deck pump line will be covered in Hessian which will be kept wet during the pour to keep the line cool and to thus assist in avoiding blockages.Electric immersion vibrators will be used for vibration of the concrete during placement The concrete will be placed from the leading edge of the form working back towards the joint generally in accordance with the sequence outlined in Appendix 5 The concrete adjacent to the construction joint in the upper portion of the edge beams and in the slab will be placed last ensuring that all dead load deflection has already occurred prior to concrete placement against the construction joint Particular attention will be given to ensure that the joint interface receives good vibration The vibrators will be rubber tipped to avoid form damage

4.5.5 Concrete Curing & Finishing

To control plastic cracking during surface finishing, an aliphatic alcohol evaporation retardant such as Parchem’s Concure AV will be applied to the freshly screeded surface as necessary to limit moisture loss in dry windy conditions

A lightweight walkway system will be provided spanning 10m from the previous deck to the front of the traveller to improve access for finishing operations A broom finish will be applied after screeding to enhance asphalt adhesion

Polyethylene sheeting will be laid over the finished concrete for curing when the surface has hardened sufficiently that the textured finish will not be damaged Upon completion, the polyethylene sheeting will be covered with a heavy matting or carpet to prevent it from being lifted by wind and to protect it from pedestrian and vehicle traffic during the curing period

Due to the presence of starter bars and stripping / traveller operations in the day after casting,

it is anticipated that there will be difficulty in maintaining the polythene sheeting in the wing area for the full curing period To ensure that adequate curing is achieved in this area, a curing compound will be applied to the deck surface from the edge of the deck to the external barrier

(i.e., the wing and motorcycle lane areas) in addition to polythene This also covers the deck surface above the edge beam

The beam sides and deck soffit will be cured with a suitable clear curing compound after stripping The proposed curing compound is Sika Antisol E or equivalent

When the deck is being constructed on a 5-day cycle, the polythene will be removed on the afternoon of Day 4 prior to early morning casting on Day 5

With careful vibration, it is not envisaged that any surface dressing will be necessary to the outside of the edge beam However, should any work be necessary in isolated areas, this will

be carried out from the dedicated platforms at the rear of the form traveller

All tie bar holes will be plugged and the joint between segments will be dressed from the rear platforms

Patching and concrete repair works will be undertaken in accordance with the latest revision of Section 7 “Concrete Repair” of Method Statement for Concrete Works”

4.5.6 Construction Joints

Each segment will be cast as one continuous pour As such, vertical construction joints will be located every 10m through the deck section These will be formed using a combination of steel and timber A suitable joint surface profile will be achieved using surface retarder painted onto the formwork face followed by high-pressure water washing after stripping

Horizontal construction joints are required for the central barriers which will be precast elements with in-situ stitches The surface profile will be achieved by using either a suitable surface retarder to be applied after concrete finishing has taken place followed by high pressure water washing, by scabbling or by green cutting

4.5.7 Construction Engineering and Alignment Correction Measures

On the morning following the casting, the following information will be submitted to the Construction Engineer under cover of the check sheets included in the Inspection and Test Plan for Cable-Stayed Bridge Deck Construction (PM1-CO-ITP-07):

• As-Built Survey

• Cable Force Record

• Load Map at time of survey and load check

• Ambient Temperature at time of survey

The cable force record will be established by undertaking a 6 strand liftoff test in parallel with the early morning survey on Day 1 of the cycle The results of this test will be provided to the construction engineer and will also be used to verify the strand force tolerance within the bundle

Based upon this information, the Construction Engineer will provide;

• The adjustment to the cable force

• The correction to the theoretical “f” value previously calculated in the step-by-step analysis The re-calculated “f” value will take into account any requirement for

“recovery of vertical alignment” which may be necessary from time to time

• The shim dimension represented by the nominated “f” value

This procedure is included on Form A of Appendix 9.

The calculation for the new “f” value will be documented for each segment The calculation will

be carried out within the constraints imposed in the Erection Manual

After launching and resetting of the traveller on day 2 of the cycle a local survey will be undertaken to check the achieved f value and to review the pod geometry This survey may be carried out at any time of the day and is not temperature dependant This procedure is included on Form B in Appendix 9

The intended deck mix design will be 50D using 480 kg/m3 of cement The expected strength gain is indicated on the 5 day deck cycle included in Appendix 1 of this document The concrete strength limitations required prior to various deck operations as nominated in the Erection Manual will be determined by either testing or projection from reliable strength gain curves Initially, all results will be determined by testing

A final local survey will be undertaken prior to casting This procedure is included on Form C of Appendix 9

4.5.8 Stay Cable Installation

The stay cables will be installed as a two stage operation

Stage 1 - Initial stay installation to be carried out after launching and re-setting traveller but

prior to concrete placement All strands are installed to a nominal load nominated in the Erection Manual The permanent lower anchorage is accessible at the bottom of the pod from the form traveller The stressing operation is carried out in the tower head

Stage 2 - On the morning after casting, stress the stay cable to the force provided by the

Construction Engineer

Stage 1 Stay Cable Installation:

Stage 1 stay cable installation will commence when:

• The traveller has been launched and re-set

• The temporary struts have been installed back to the last cable pod

• The cable pods have been stressed to the traveller

• The precast cross beams have been installed and the installation of rebar

has reached a suitable stage to suit the construction cycle

Installation and tensioning of stay cables will be carried out in accordance with the method statement for stay cable installation noted in Section 1 of this method statement A brief summary is as follows:

Strand dispensers with strand drums will be set up for each of the two (2) stay cables on the previously cast deck segment during launching of the form traveller The cutting bench and deviator wheel will be set up on a suitable platform supported above the rebar at each cable position when the traveller has been set in position after launching

The cable sheath will be assembled on the deck in complete cable lengths to suit individual cables with the top end within reach of the tower crane The reference strand (a strand of known accurate length supplied by the strand supplier) will be installed into the respective sheath At the time of cable installation, the sheath complete with reference strand will be lifted

by the tower crane and attached to the flange end of the formwork tube which is flush with the tower surface

The guide tubes have been designed with a flange sitting flush with the face of the tower concrete A temporary angle bracket will be fixed to the outside of the tube end so that the sheath can be secured The strand will then be manually pushed through the correct hole in the top anchorage block For this operation access is required to the outside face of the tower.

Flush ended guide tubes with angle bracket for sheath attachment

Attachment of cable sheath Note the single strand in sheath for initial erection

Access at tower head level will be provided by hanging platforms located on the outside of the tower head and permanent platforms inside the tower head Access to the external platform will be via the man hoist and access to the internal platforms will generally be via ladders and platforms down from the jump form or later, down from the top of the tower

Hydraulic winches will be located both at deck level and inside the tower head to hoist each individual strand up to the tower head as it unreels from the drum The winch line will be connected to a device known as a shuttle which is in turn connected to either one or two strands depending on the cable installation operation The shuttle enables the strand to be pulled up the sheath without twisting and tangling with previously installed strand.

Return of shuttle to deck level

Strands connected ready for winching to tower headWhen the strand has been fixed into the top anchorage the lower end will be cut to length at deck level and the free end will be pushed manually into the correct hole in the lower anchorage This is done by looping the free end of the strand at deck level and pushing it through the end of the guide tube The permanent wedges will be installed as each strand is installed into its respective anchorage position

Each strand will be stressed individually to a nominal force provided by the construction engineer prior to the installation of the next strand using the Freyssinet Isotension system described elsewhere The live end will be located in the tower head After each strand installation the winch line with the shuttle will be returned by the winch at deck level for the next strand.

Stage 2 Stay Cable Adjustment:

On the next day after casting of the segment, the strands in the stay cables will be individually tensioned to a force which will be calculated by the Construction Engineer The force calculation will be made on the basis of the as constructed survey and the load mapping which will be completed early in the morning and provided to the Construction Engineer by the deck construction team

Stage 2 stay cable adjustment will commence when:

• The concrete has been cast and has achieved the strength nominated in the

Erection Manual This will occur on day following the casting of Segment n;

• The as-constructed survey, the load mapping and other relevant information has

been completed by the deck team and provided to the Construction Engineer;

• The construction engineer has provided the calculated cable force;

• The initial stressing of the cross beam has been completed

Installation of free-end strand loop into the bottom anchorage.

Erection of Cable Sheath – Panama Bridge

Assembly of Cable Sheath – Panama Bridge

Stay Cable Erection in Panama Bridge(Note that the stay cable for PMB will be installed on the traveller prior to casting.

The cable force adjustment will be carried out just prior to launching.)

Dual Strand Dispensers and Coils (3-tonne coils)

4.6 Restrictions on Deck Crane Movements

The crane location for installation of pods and cross beams shall be in accordance with the description provided in Sec 4.5.3 and the sketch included in appendix 2 of this document The crane shall not travel onto the segment until the rear cross girder tendon has been fully stressed.

4.7 Buffeting Cables

The buffeting cables provide horizontal restraint against rotation of the cantilever in the horizontal plane These consist of temporary stay cables between the top of the deck and the pile cap with a cross braced arrangement The detailed design of the cable assembly with top and bottom anchorages will be provided by Cardno The top anchorage will be located above the deck and will be seated on a frame that will enable the cable anchorage to be located square to the cable axis The cable will pass through a penetration in the deck

In normal wind conditions the approach span buffeting cable remains in tension while the main span cable is slack In the event of a forecast high wind event reference shall be made to the relevant stage drawing and the allowable wind speed for deck erection drawing (D-B-022) contained in the deck erection manual for the necessary action

The provision of 80 tonne ballast as noted in the above referenced drawing will consist of a combination of plant (deck crane and Manitou) together with precast elements as necessary (pods and cross beams)

The Deck Engineer (Project Engineer Bridge Deck) will be responsible for monitoring the wind forecasts

Details of the buffeting cables and the anchorage structures will be provided on drawings The installation sequence is provided in the Erection Manual

Refer to Appendix 11 for the Method Statement for Buffeting Cables and Temporary Tiedown Cables prepared by Freyssinet

4.8 Temporary Tie down Anchor

As with the buffeting cables, the detail will be provided by Cardno on drawings These cables will apply a prestress in the tower and the deck as resistance against wind forces The sequence of loading and de-loading the buffeting cables and the temporary tie down anchors will be defined in the Erection Manual produced by Cardno

In normal wind conditions the temporary tie down anchor and the main span buffeting cable are both stressed In a forecast high wind event the procedure described in the buffeting cable section above shall be adopted

MTB: Second pair of buffeting cables installed on the main span.

4.9 Lands ide Closure Pour

As shown below, there are two landside closure pours for Phu My Bridge Project; one on District 7 linking D7 bridge deck to D7 West Tiedown Pier and the other on District 2 linking D2 bridge deck to D2 East Tiedown Pier The landside closure is about 1.5m in length and will begin after Segment 15 on both mainspan and sidespan has been completed The procedure for landside closure pour describe below is the same for both D7 and D2 closure pours but the reference document and drawings should be referred separately for each work