7 4 ok CW2C PRESTRESSED GIRDER

CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 CONSTRUCTION METHOD STATEMENT FOR PRODUCTION OF PRESTRESSED GIRDERS 1/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 TABLE OF CONTENTS I PRESTRESSED CONCRETE II CONSTRUCTION METHOD FOR SUPER TEE GIRDERS III CONSTRUCTION METHOD FOR VOIDED SLAB GIRDERS 2/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 I PRESTRESSED CONCRETE MATERIAL REQUIREMENTS 1.1 REFERENCE STANDARDS AASHTO M235 Epoxy Resin Adhesives 22TCN 272-05 Specification standard for Bridge design AASHTO LRFD Bridge Design Specifications, Deflection Criteria for Girders, Section 2.5.2.6.2 ASTM A421-91 ASTM A416-99 Un-coated Stress Relieved Steel Wire for Prestressed Concrete; Steel Strand, Un-coated Relieved Strand for Seven Wire Stress Pre-stressed Concrete ASTM A722M-07 Uncoated High Strength Bars for Pre-stressing Concrete EURONORM prEN Tendons (15.7mm) for Pre-stressed Concrete 10138 1.2 MATERIAL FOR PRESTRESSED CONCRETE a) PRESTRESSING STEEL High tensile strength steel wire shall be stress relieved and shall conform to the requirements of ASTM A421-91 or equivalent for Un-coated Stress Relieved Steel Wire for Pre-stressed Concrete High tensile steel strand with low-relaxation shall be weld free and stress relieved after stranding and shall conform to the requirements of ASTM A41699 or equivalent Steel Strand, Un-coated Seven Wire Stress Relieved Strand for Pre-stressed Concrete High strength steel bars shall confirm to the requirements of ASTM A722M or equivalent for Uncoated High Strength Bars for Pre-stressing Concrete Testing of pre-stressing reinforcement shall be in accordance with the requirements of the ASTM Specifications for the type of system intended to be used or subject to approval by the Engineer b) ANCHORAGES FOR POST TENSIONING All anchorage assemblies shall be subject to the approval of the Engineer All post-tensioned pre-stressing steel shall be secured at the ends by means of approved permanent type anchoring devices The Contractor shall submit information and details, including test certifications for by the Engineer 3/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 End anchorage devices (stress and dead anchors) shall be designed and manufactured for the types of tendons to be used They shall have a previous service record of performance and durability when used on similar type work All anchorage devices for post-tensioning shall be capable of holding the prestressing steel at a load producing a stress of not less than 95 percent of the guaranteed minimum tensile strength of the pre-stressing steel Fixed anchorages for tendons in pre-cast beams shall be of steel bearing plate type while all remaining anchorages shall be those capable of adjustment by means of a threaded anchor head and ring nut It shall be the responsibility of the Contractor to confirm the required bursting reinforcements in the local zone for the particular shape and design of the anchorage devices proposed All externally exposed steel parts shall be protected from corrosion All threaded parts and fittings shall be protected by greased wrappings or plugs until used Anchorages shall be kept free from dirt, mortar, loose rust or other deleterious materials Damaged anchorage parts shall not be used c) DUCTS (SHEATH) Ducting for internal tendons shall be fully compatible with the proposed pre-stressing system The ducts shall be fabricated from corrugated galvanized sheet steel or corrugated thick-walled HDPE conduit Minimum follows: duct thickness shall be as * 26 gauge for duct diameter less than or equal to 67 mm * 24 gauge for duct diameter greater than 67 mm * 31 gauge for bar tendons Ducts shall have grouting connections at each end and shall have vent/drains at all intermediate high and low points, subject to the approval of the Engineer d) GROUT FOR DUCTS Unless otherwise specified in other prevailing sections or subject approval by the Engineer as a result of grouting trials, the grout shall: to  Consist only of ordinary Portland cement, water and expansive admixtures approved by the Engineer and used in accordance with the manufacturer’s instructions;  Have a water to cement ratio as low as possible consistent with the necessary workability, and under no circumstances shall the water/cement ratio exceed 0.40;  not contain admixtures containing chlorides, nitrates or similar electrolytic conducting materials Premixed grouting material shall be used e) CONCRETE 4/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 Concrete shall be of the class indicated on the drawings and shall conform to the requirements of Specification - Concrete and Concrete Structures and the requirements specified below unless otherwise stated on the drawings or as may be required by the Engineer The maximum size of aggregate for use in the manufacture of pre-stressed concrete shall be 25 millimetres The main properties of concrete such as compressive strength after 28 days, Modulus of Elasticity (Young Modulus), and other properties that were used for the detailed design shall be confirmed by testing of samples of the approved mix design The Contractor shall perform the tests in accordance with the appropriate standards, or as may be required by the Engineer CONSTRUCTION REQUIREMENTS The Contractor shall assign an experienced technician, skilled in the use of pre-stressing system, who shall supervise the work being performed in compliance with these specifications and to the satisfaction of the Engineer The Contractor shall provide all equipment necessary for construction and prestressing The equipment shall be of a currently manufactured model, and shall be in good working condition A pre-stressing system approved by the Engineer shall be used If hydraulic jacks are used they shall be equipped with accurate pressure gauges The combination of jack and gauge shall be calibrated and a graph or table showing the calibration shall be provided to the Engineer Should other types of jacks be used, calibrated proving rings or other devices shall be furnished so that the jacking forces may be accurately known The requirements for concrete construction in Specification - Concrete and Concrete Structures shall be complied with, except as may be modified in this specification Pre-stressed concrete shall be formed, stressed, placed, cured, and protected at shops, manufacturing plants, and locations where the fabrication of such members may be properly inspected and controlled and approved by the Engineer Vertical alignment and girder lengths shown on the drawings represent dimensions at the time of final creep Deflection criteria for girders shall be in accordance with 22 TCN 272-05, longitudinal deflections may be rectified by an appropriate approved method 1.1 PLACING STEEL All steel reinforcement shall be accurately placed in the position shown on the drawings and rigidly held in place during placing and setting of the concrete Distance from the forms shall be maintained by stays, formwork spacers, ties, hangers, or other approved support Formwork spacers for holding units from contact with the forms shall be of approved material, shape and dimensions Layers of reinforcement shall be separated by suitable wire spacers Wooden blocks shall not be used 1.2 PRETENSIONING METHOD The pre-stressing elements shall be accurately held in position and stressed by jacks Stressing shall be applied to produce the stresses required in the wires, strands or bars immediately after the anchorage as shown on the drawings or as directed by the Engineer Suitable allowances shall be made for friction in the jacks and for slip and yield in the grips or anchorages Curing shall be by steam methods, or other methods subject to the approval of the Engineer 5/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 A record shall be kept of the jacking forces and the elongations produced and the minimum age in hours of the concrete for each unit until the time the tendons were released No bond stress shall be transferred to the concrete, nor shall end anchors be released, until the concrete has attainted a compressive strength of not less than 85% of the specified 28-day strength as shown by standard specimens cured in a similar fashion to the element The elements shall be cut or released in such an order that eccentricity of pre-stress is minimized subject to the approval of the Engineer 1.3 POST-TENSIONING METHOD Post-tensioning shall be carried out in accordance with an approved method, with an approved control method, and in the presence of the Engineer unless permission has been obtained to the contrary Immediately before tensioning, the Contractor shall prove that all tendons are free to move in the ducts Each anchorage device shall be set square to the line of action of the corresponding post-tensioning tendon and shall be securely fixed in position and gradient to prevent movement during the placing and compaction of concrete Except where dead-end anchorages are cast in the concrete, tendons shall not be installed until just prior to stressing Tendons shall be pulled or pushed through the duct in such a manner as to avoid damage to either the tendon or the duct Unless approved otherwise, concrete shall not be stressed until test cylinders taken from it have attained a compressive strength of not less than 80% of the specified 28-day strength as shown by standard specimens cured in a similar fashion to the element unless specifically noted otherwise on the drawings The test cylinders shall be cured in conditions similar to the concrete to which they relate in a manner approved by the Engineer Where members consist of jointed elements, the strength of transfer of the jointing material shall be at least equivalent to the specified strength of the members The Contractor shall establish the datum point for measuring extension and jack pressure to the satisfaction of the Engineer Allowance shall be made for the friction in the jack and anchorage for pull-in of the tendon during anchorage The tendons shall be stressed at a gradual and steady rate until the required extension and tendon load are reached or are approved by the Engineer The sequence of stressing shall be as shown on the drawings or directed by the Engineer The force in the tendons shall be obtained from readings on a load cell or pressure gauge incorporated in the equipment and the extension of the tendons measured The extension of the tendons under the approved total forces shall be within the limits given below of the agreed calculated extension Transverse Tendons for Segments: tendon ±10% average for one ± 7% for average of one segment 6/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 Longitudinal Tendons for Segments ± 5% All other Tendons ± 5% If the measured extensions are not within the specified tolerance then the Contractor shall submit to the Engineer his method of rectifying the discrepancy When the pre-stressing force has been applied to the satisfaction of the Engineer, the tendons shall be anchored The force exerted by the tensioning apparatus shall then be decreased gradually and steadily so as to avoid shock to the tendon or anchorage Full records shall be kept of all tensioning operations including measured extensions, pressure gauge or load cell readings and draw-in at anchorage Copies of records shall be supplied to the Engineer within 24 hours of each tensioning operation A check shall be made of pre-camber and if significantly different to the calculated value, the Contractor must investigate before construction of further girders Unless otherwise agreed by the Engineer, tendons shall not be cut less than days after stressing 1.4 GROUTING a PLANT FOR GROUTING The grout mixer shall produce a grout of colloidal consistency The grout injector shall be capable of continuous operation with a sensibly constant pressure up to 0.70-N/mm2 and shall include a system of circulating or agitating the grout whilst actual grouting is not in progress All baffles to the pump shall be fitted with 1.18 mm sieve strainers The equipment shall be capable of maintaining pressure on completely grouted ducts and shall be fitted with a nozzle that can be locked off without loss of pressure in the duct The pressure gauges shall be calibrated before they are first used in the Works, and thereafter as required by the Engineer All equipment shall be thoroughly cleaned and washed with clean water at least once every hours during the grouting operations and at the end of use for each day During the grouting operation, the Contractor shall provide adequate flushingout plant to facilitate complete removal of the grout in the event of a breakdown of the grouting equipment or other disruption before the grouting operation has been completed b GROUTING OF DUCTS AND SHEATHING Grouting trials shall be undertaken when directed by the Engineer Prior to using the grout in any trial or in the works the Contractor shall submit a detailed method statement for grouting procedures covering proposed materials, sheathing, anchorage and vent alignment equipment, and quality control to the Engineer for his approval All ducts shall be thoroughly cleaned out by means of flushing with water and/or water/compressed air Grouting of ducts shall be carried out as soon as it is technically practicable, but not more than weeks after the tendons inside the ducts have been stressed, and the Engineer’s permission to commence grouting has been 7/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 obtained If due to the requirements of the stressing procedure, tendons cannot be grouted within weeks the sheathing shall be sealed to protect the tendons from corrosion Injection shall be continuous and slow enough to avoid producing segregation of the grout The method of injecting grout shall ensure complete filling of the ducts and complete surrounding of the steel Grout shall be allowed to flow from the free end of the duct until its consistency is equivalent to that of the grout injected The opening shall then be firmly closed Any air vents shall be closed in a similar manner one after the other in the direction of flow The injection tubes shall then be sealed off under pressure until the grout has set The filled ducts shall not be subjected to shock or vibration within day of grouting Not less than days after grouting the level of grout in the injection and vent tubes shall be inspected and made good as necessary The Contractor shall keep full records of grouting including the date when each duct was grouted, the proportion of the grout and any admixtures used, the pressure, details of any interruptions and topping up required Copies of these records shall be supplied to the Engineer within days of completing grouting c PROTECTION OF PRESTRESSING ANCHORAGES As soon as possible after tensioning and grouting are completed, exposed end anchorages, strands and other metal accessories shall be cleaned of rust, misplaced mortar, grout and other such materials Immediately following the cleaning operation the entire surface of the anchorage recess and all exposed metal shall be thoroughly dried and uniformly coated with an epoxy bonding agent conforming to AASHTO M235 Class III in accordance with the manufacturer’s recommendations The anchorage recess shall then be filled with an approved non-shrinkage mortar The mortar shall not contain aluminium powder, iron particles, chlorides, sulphates, fluorides or nitrates Where the protection will form part of the exposed works, the anchorage recess shall be filled with concrete of the same quality and colour as that of the adjacent concrete and shall be applied and cured in accordance with these specifications or as may be required by the Engineer Exposed surfaces of anchorages not in an anchorage recess shall be coated for corrosion protection with a coal tar epoxy or equivalent as approved by the Engineer Prior to coating, all surfaces shall be wire brushed to remove all loose rust, mill scale or other deleterious substances, and the surfaces cleaned with a suitable solvent to remove oil and grease CURING Except as specified herein or otherwise approved, wet (water) curing shall be provided in compliance with the requirements in Specification - Concrete and Concrete Structures If the Contractor elects to cure by any other method, the method and details shall be subject to the approval of the Engineer STEAM CURING A steam curing process complying with the following conditions may be used as an alternative of water curing, if proposed by the Contractor and subsequently approved by the Engineer a) The casting bed for any unit cured with steam shall be completely enclosed to prevent steam from escaping and exclude the outside atmosphere 8/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 b) Two to four hours after placing concrete and after the concrete has undergone initial set, the first application of steam shall be made If retarding admixtures have been used, the duration before application of the steam shall be increased to four to six hours c) Water curing methods shall be used from the time the concrete is placed until steam is first applied d) The steam shall have a relative humidity of 100% to prevent loss of moisture and to provide moisture for proper hydration of the cement e) Steam shall not be directly applied to the concrete During the application of the steam, the ambient air temperature shall increase at a rate not exceeding 22°C per hour until the maximum temperature is reached and shall be held until the concrete has reached the desired strength f) In discontinuing the steam application, the ambient air temperature shall not decrease at a rate exceeding 22°C per hour until the temperature has reached 10°C above the temperature of the air to which the concrete will be exposed g) The maximum curing temperature shall be from 60° to 67°C HANDLING, TRANSPORT AND STORAGE Pre-cast pre-stressed concrete shall not be moved from the casting position, or transported, until the concrete has attained a compressive strength of 90% of the specified 28-day strength Extreme care shall be exercised in handling and moving concrete members Pre-cast girders and slabs shall be transported in an upright position, shock shall be avoided and the points of support and directions of the reactions with respect to the members shall be approximately the same during transport and storage as when the members is in its final position If the Contractor deems it expedient to transport or store pre-cast pre-stressed units in other positions than this, it shall be done at his own risk after notifying the Engineer of his intention to so Any unit considered by the Engineer to have become substandard shall be rejected and replaced by an acceptable unit at the Contractor’s expense MARKING OF PRECAST PRESTRESSED MEMBERS Each pre-cast pre-stressed member shall be uniquely and permanently marked so as to show its type and date of casting ERECTION OF PRE-CAST BEAMS CONFIRMATION OF POSITION Prior to the erection of the beams the Contractor shall survey the positions of the supporting columns and confirm with the Engineer on the positions, both horizontal and vertical, of the supports The Contractor shall, at his own expense, make all necessary adjustments to the bearing seating and beam length to ensure that completed decks are true to line and level Any proposed deviation of beam length from that given in the drawings shall be agreed by the Engineer before the beam is cast 9/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 ERECTION The method statement shall be submitted to the Engineer for his approval within one month of the commencement date The statement shall particularly include but not be limited to the use of lifting and transfer gantries supported on the new structure and particular locations The statement shall include full details of the equipment to be used to handle beams and to incorporate them into the structure The method statement shall be accompanied by full structural calculations and appropriate workshop drawings for each stage of the procedure The calculations shall be appropriate for such temporary works and shall take into full consideration all temporary loading cases arising from the procedures, the prevailing conditions at the site, in particular likely wind loading, and the nature of the existing ground The Contractor shall carry out all additional soils investigation necessary to confirm his assumptions concerning the nature of the existing ground The calculations and drawings shall be certified and stamped by a qualified structural engineer experienced in the preparation of such details The details shall include consideration of the effect of each stage of the procedure on the completed permanent works on which the gantry is to be mounted and operated The procedures for lifting and transferring the beams into position and the order of erection of the beams shall be such that the eccentricity of loading on the completed permanent works (supporting piers and the foundations) is minimized When beams are being placed in position they shall be braced against overturning before being released by the crane or other lifting devices Beams shall be prevented from moving laterally during the placing of in-situ concrete The lifting and placing of beams will not be permitted to commence until such time as the Contractor’s method statement, calculations and shop drawings have been reviewed and approved by the Engineer II Construction Method for Super Tee girders Number of Tensioning pedestals and formwork SUPER-TEE beams are the pre-stressed concrete beams The prestressing strand will stressed released on the tensioning pedestals When the concrete beam has reached 85% required strength to conduct cutting prestressing strand so as to produce stress in the prestressing strands and concrete of beams External and inner formworks and shuttering of steel hangers, steel beams and inner formwork shall be fabricated in two sets for each Design of tensioning pedestals and formworks 2.1 Pre-stressed tensioning pedestals Structure of tensioning pedestals to ensure convenience for placing reinforcing steel and pre-stressing steel to ensure adequate and convenient space for the erection and removal of formwork, concrete supply, placing concrete and lifting casted beams then promptly transport to the storage platform The position of the tensioning pedestal must be in high places to ensure good drainage, the tensioning pedestal to ensure absolutely no settlement 2.2 Formwork Fabrication and erection of formwork shall be in the correct position.It should be easy to erect and remove the formwork The joints must be parallel or 10/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 III Construction Method for Voided Slab girders Cycle time of PC slab - Girders Fabrication Rebar and PC Installation ( R ) day Formwork ( F ) day Stressing and Concrete casting ( CC ) day Form Removal ( FR ) day Curing (C) day Cutting PC strand and side shifting (SS) day Total 20/ 34 6days PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 Description of work sequence a Preparation works  Construction of casting bed • Site preparation for production yard shall be carried out before mobilization of necessary materials and equipments for the production of PC slab – Girder • The location of casting bed shall be compacted to prevent settlement during the application of load • The working area shall be level as possible and stable for good mobility of equipments • For foundation of casting bed, existing unsuitable soil such as mud of organic soil shall be replaced to suitable soil and compacted adequately to prevent settlement of casting bed • • Order construction of casting bed is as follows: - Construction of sub-base - Installing formwork, rebar and pouring concrete bottom of casting bed - Installing formwork, rebar and pouring concrete of longitudinal beam - Curing concrete in the 14 days Stability of casting bed shall be confirmed by static loading test on representative some beds prior to commencement of production • Checking condition and elevation of casting bed shall be taken during production of PC slab –Girder even result of static load is satisfactory with criteria for acceptance  Mobilization • Material and equipment for the work shall be set up And required approval such as for material testing and calibration of stressing jack and pump shall be confirmed • Prior to commencement of work, all equipment and workers shall be inspected with attendance of the Engineer • Approval working drawing for PC slab- Girder shall be confirmed prior to commence production of PC slab- Girder 21/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 b Fabrication of reinforcing steel bar • Details of reinforcing steel bar such as arrangement, location, dimension and shapes shall be shown on working drawings in accordance with Contract Drawings • Rebar shall be fabricated in accordance with the shape and dimension as shown on approved working drawing • Material test of rebar shall be carried out in accordance with Special Specifications • Bar cutter equipment or other proper equipment shall be used for cutting rebar Bar bending equipment or manual bending shall be used for bending rebar to form the shape and dimension as shown on working drawing • Fabrication of rebar shall be carried out by cold cutting and cold bending Rebar fabrication by application of heat shall be in accordance with the Engineer’s instruction c Setting bottom form Formworks shall be in accordance with the shape, lines and dimension shown on working drawings Forms shall be constructed to prevent deformation due to applied load Tolerances Wrong number of dimensions ± mm False heart of formwork ± 5mm The length of produced girder shall be confirmed on approved working • drawings Bottom form shall be prefabricated metal form Elevation of bottom form • shall be inspected by survey in accordance with the designed pre-camber of PC slab-girders if any At that time, the condition of casting bed shall be visually checked such as gap between forms and foundation or damage on foundation Confirmation (calculation) of pre-camber will be submitted separately All forms shall be cleaned, free from dust, grease or other foreign matter • and shall be treated with approved form release agent before installation Gap between the forms joint may be in-filled by packing to prevent • 22/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 leakage of cement mortar during casting Bottom forms shall be set in accordance to specified length of PC slab-girders shown on approve working drawings d Installation of rebar Rebar including embedded rebar for diaphragm shall be installed in • accordance with approved working drawings Concrete blocks with whip shall be used as spacer Spacer shall be • installed at bottom and side of rebar in order to maintain the appropriate concrete covering Sample of concrete spacer shall be inspected and tested for approved by the Engineer Fixing and splicing of rebar shall be done by iron wire Splicing length and • location shall be in accordance with working drawing Ties at intersection of rebar shall be installed sufficiently to prevent dislocation during casting Rebar shall be tied at all intersections Fixing by welding shall only be carried out if shown on approved working drawing or as instructed by the Engineer Installed rebar shall be free from rust, dirt, oil or other material that might reduce the bond Temporary embedded materials shall be installed at proper locations • Details shall be shown on working drawings Location of temporary embedded materials shall be neatly finished with cement mortar after their role The mortar shall be mixture of cement and fine aggregates in the same proportion Typical procedure of finishing works is shown on ● Inspection and approval by the Engineer shall be carried out prior to setting of forms ● Rebar fabrication by application of heat shall be in accordance with the Engineer’s instruction Tolerances 23/ 34 The distance between the bars ± 10 mm Steel joints 35D ±20mm Length of steel ± 10mm PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 e Installation of side forms Pre-fabricated metal form panels shall be used for side forms Layout of • forms shall be installed in accordance with design of forms cased on approved working drawings Tolerances Wrong number of dimensions ± mm False heart of formwork ± mm Temporary support shall be installed properly in accordance with design of • form Details of forms including supporting system will be submitted separately All forms shall be cleaned, free from dust, grease or other foreign matter • and shall be treated with the approved form-release-agent before installation Triangular fillets not less than 10mm x 10mm to form smooth straight • chamfers shall be applied to all sharp edges of the exposed surface of PC slab-Girder Holes on side form for embedded rebar for diaphragm shall be made at • proper location with proper dimension in accordance with approved working drawings Clearance around embedded rebar on forms shall be closed by cotton waste or other proper material to prevent leakage of cement past during casting concrete as far as possible Gap at joints of forms shall be in-filled by packing to prevent leakage of • cement past of casting concrete The gap between metal form and supporting beam shall be also in-filled by suitable material such as cleat to prevent displacement of forms Before closure of forms, inside of forms shall be cleaned properly If • cleaning inside form is unsatisfactory for acceptance under inspection of the Engineer after closure of forms and before casting of concrete, some of form will be opened and cleaning shall be carried out again for acceptance After completion of installation of forms, inspection shall be held in • attendance with the Engineer for approval to cast concrete ● Design calculation of forms shall be submitted together with submission of form drawing Stressing PC Tendon 24/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 a Preparation works • Prior to commencement of works, all equipment and worker shall be inspected with attendance of the Engineer • Checking the technical certificate of high strength steel • Checking the technical certificate of anchor • Checking the error when setting high strength steel bunch • Checking and adjustment tensioning equipment (jack), pressure gauge will be used If the calibration term is over, new calibration should be done • Calibration of pre-stressed jack and pump shall be carried out by approved authorized laboratory with attendance of the Engineer • Certificate of above calibration shall be reported to the Engineer for approval, which shall show the relation of reading manometer and actual applied force by jack Combination of jack and pump shall be clarified • Determine coefficient of friction of jack and hooped anchor (separate determination should be done for every jack) • Checking practice on operation safety • Side forms and support have been installed prior to stressing b Installation of anchorages and wedges • Surface of casting of anchorage shall be clean from laitance of concrete to prevent the occurrence of gap between jack beam and end-anchor block prior setting End-Anchor Block • End-anchor block and wedge shall be check and clean from dirty and corrosion And it shall be kept properly at the time of installation and shall not put ground directly • Prior to install anchor blocks and wedges, lubricating grease or wax will be applied on surface of wedging hole on anchor blocks in order to ensure to draw in wedges properly during pre-stressed Grease shall be applied by with cotton waste for each hole one by one Grease shall not be applied to wedges and strand c Setting of jack and pump for pre-stressed 25/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 • Approved combination of stressing pump and jack shall only be used in carrying out pre-stressed Pre-stressed Jack shall be installed at both end of anchor location of girder • Jacks shall be installed on axis of PC cables in order to prevent non-uniform stressing on one tendon • Installation of jack shall be carried out using crane or chain block attached to a frame Jacks shall keep proper location with hanging prior to commencement of pre-stressed • After setting jacks, hydraulic pump shall be connected to jacks with confirmation of approved combination • Required actual reading manometer for each step of pre-stressed in accordance with calibration result of jack and pump shall be summarized on table and shown at site • Persons who in charge pre-stressed works No Person Chief Site Engineer Description of Role Control Pre- stressed Site Engineer Making Control Chart Operator Operation Pump Skilled Worker Checking Elongation 26/ 34 Skilled Worker for General work Surveyor Check EL of girders PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 • Protection board shall be set behind jack for safety And notice to keep off behind jack during pre-stressed shall be got across all relative persons working on site And pre-stressed area shall be enclosed by safety tape to prevent unauthorized persons go into pre-stressed area d Stressing of PC tendon • Prior to stressing, all side forms and support shall be installed • Stressing shall be carried out with the attendance of the Engineer • Procedure of pre-stressed is implemented by periods According to the following chart:  Initial pre-stressing • Pre-stressed shall be applied by both jacks • Marking by splay color shall be provided on PC cables at end of anchor block in order check visually slipping strand in jack during pre-stressed or slipping wedging strand after pre-stressed • And pre-stressed shall be applied up to 0.1Pk again and marking on strands shall be provided in order to measure elongation during pre-stressed as shown figure • Contacting condition between anchor block and jack beam and between surface of jack and anchor block shall be checked • If there are some gaps for the above checking or eccentric of jack on axis of PC cables visually, pressure on jack shall be released to again and initial prestressed shall be applied again with 0.1Pk  Pre-stressing up to final - Step 1: Jacks stretch to 0.1 PK, mark to measure elongation 27/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 - Step 2: Jack stretch to 0.2 PK and stop Measure elongation of cable - Step 3: Jack stretch to 0.4 PK and stop Measure elongation of cable - Step 4: Jack stretch to 0.6 PK and stop Measure elongation of cable - Step 5: Jack stretch to 0.8 PK and stop Measure elongation of cable - Step 6: Jack stretch to PKV (1÷1.05Pk) and stop Rest minutes Measure elongation of cable - Checking , comparing elongation actual with elongation calculations + If tolerance between elongation actual and elongation calculations from 0÷5% => stressing final + If the elongation actual is smaller than elongation calculation the new force will be added The additional force shall be provided by the supervision consultant engineer decided at site construction - During stretching, continue to measure expansion factor and deformation of girder Compared with design number  Calculation elongation actual of cable 28/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 1.1.1.1.1.1 ∆L = ∆L1 + ∆L2 ( mm ) In which: : ∆L1: Value cable elongation to measure stress from tune cable up 0.1P to maxximum stress ∆L2 : Value cable elongation alowable stress design to tune cable up stress 0.1P  Technical requirements of high strength bunched cables stretching process • Pk not exceed the maximum tensile stress exceeds specified in the 5.3• 22TCN247-98 (80% stress criteria) The difference in the actual value of elongation compared with calculations to • ≤ 5% Check stretching force by chronometer with accuracy 2% Elongation is • measured with accuracy 1mm Remedial measure of works in case problem occur during stressing During stressing, when the problem occurs, the contractor shall be immediately informed to the consultant engineer Problem Remedial measure 1.When one or more wire is suddenly cut - wire shall be cut, may consider accepting during stressing - More wire or one strand shall be cut, contractor shall be replaced the bunched cable 2.After stressing, if one or more strands Additional pre-stressing were succeeding anchorage already stressed and after minute the strand drew back its length 30 force to be for stress compensate its losses e Decrease stressing pressure and removal of jack 29/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE the to CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 • After measure elongation at final pre-stressed force, pressure on jacks shall be released up to 0.1Pk And pull-in shall be measured and calculated in consideration of residual elongation of PC cable in jacks under pressure 0.1Pk • It shall be confirmed that actual pull-in is less than allowable pull – in • After measuring pull-in, pressure on jacks shall be release all And jacks shall be removed • Jack shall be set on next PC cable and continue same sequence of prestressed as above mentioned • After pre-stressed all PC cable per girder, elevation of top of girder shall be surveyed at same locations of initial survey in order to check camber due to pre-stressed Concrete casting for PC slab girder • Casting shall be carried out layer by layer of approximately 40cm and casting concrete shall be proceeded from one end going to the opposite end • The vibrators shall be of type with proper frequency The number of vibrators shall be sufficient to consolidate the concrete properly within 10 minutes after it is deposited in the forms At least spare vibrators shall be available on standby at site to maintain immediate continuity in case of breakdown • Vibrator shall be penetrated into the previously cast layer through the new casting layer • Operation of vibrator shall be taken care not to damage strand tendon • Concrete vibrators will not be used to transport concrete inside the formwork during casting • Concrete condition shall be closely monitored to avoid concrete to harden before casting the next layer The new concrete shall be placed within maximum hours after placing the previous below contact layer • Splattered and loose concrete on surface of form shall be removed before placing concrete • Tightness of the formworks shall be inspected and monitored regularly during casting to prevent deformation or displacement of forms and leaks at the formworks In case displacement occurs, they shall be immediate adjusted to before concrete placing continues 30/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 • Installed rebar shall be taken with care to prevent dislocation during casting concrete In case dislocation occurs, they shall be immediate adjusted to before concrete placing continues • Casting speed shall be monitored not to exceed the designed pressure considered on the design of formwork • After placing concrete, splattered concrete on rebar shear connectors shall be cleaned Concrete surface shall be hand finished using steel trowel at least times including the final finishing Tolerance in casting height shall be ±5mm In case of emergency and it is necessary to stop placing concrete before a section is completed, following measure shall be taken - To make the surface level until the last available mix of concrete and joint shall be treated and considered as construction joint - Extra specimens for concrete compressive test shall be taken from emergency stopped concreting area in order to confirm the strength of concrete at the corresponding section - In case of rainfall, pooling water shall be removed on the surface of concrete before making the surface level And plastic vinyl sheet shall be installed covering all areas of concreting - In emergency case due to crane or bucket breakdown, broken crane or bucket shall be replaced with standby one Another one set of crane and bucket shall be prepared for stand-by - However, it is subject to rejection of girder which has such construction joint with inspection and evaluation by the Engineer Detailed report on nonconformance shall be made if such emergency case will be occurred Removal of forms and curing of concrete • Exposed surface of girder (top surface of girder) shall be covered by vinyl sheet immediately after final finishing of concrete surface • After one day of casting concrete, side forms shall be dismantled • Immmediately after forms have been removed and finishing completed, all concrete shall be cured by one of the following methods The Engineer will specify the concrete surface which may be cured by either method • In case of rainfall, plastic vinyl sheet shall be installed covering all area of concreting 31/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 • Water method – the entire exposed surfaces other than slabs shall be protected from the sun and the whole structure shall be covered with the burlap, cotton mats, or other suitable fabric for a period of at least days • Removal of forms shall be taken care not to damage or injure concrete surface and embedded rebar of girder • In case that the girders will be stocked for a long time after casting, surface of embedded exposed rebar such as for diaphragm and deck slab shall be covered by cement paste to prevent corrosion and rust • After removal of forms, surface of concrete where diaphragm will be constructed shall be treated with chipping as construction joint Cutting PC Tendon and measuring camber  Cutting of PC tendon • Checking the concrete strength, if 90% of design strength is achieved, tensioning is permitted to be execution • Side forms and support have been removed prior to cutting • The strand cutting sequence is the same as that of tensioning • The strands will be cut carefully, separately and simultaneously at both ends with oxyacetylene fire at distance of 40 cm from internal face of jacking beam Oxy-acetylene fire shall be moved back and forth in a distance of 30 cm to heat up the strand until it is broken The heating period of time for each strand shall be from to minutes The total cutting time for each girder shall last about 40 minutes • Cutting of PC tendon results have been approved by the Engineer  • Measuring deflection of girder Three points shall be marked to monitored deflection of girder: One point at middle, other points at two heads of PC girder Three points shall be the same elevation • After each step of loading force the elevation of checked points shall be measured by leveling machine • The final pre-camber of the girder shall be approved by the Engineer 32/ 34 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 Side shifting girder to stock • After prestressing is completed, PC slab-girders shall be shifted to stock from casting bed by tow crane Treatment of End of PC I girder • Re- cutting prestressing strand by machine The Ends of prestressing strands are protected with a layer of epoxy (Sikadur732 or conresive 2525) gel with minimum thickness of mm Main construction equipment: Names of construction equipment 33/ 34 Unit Quantities Concrete Batching Plant 30 - 60m3/h set Concrete Pumping machine 60m3/h set Mix Truck ≥6m3 car Concrete Mixing machine ≥750l set Front Loader ≥2,4m3 set Barge ≥ 250T set Barge ≥ 30T set Crawler or Moblie Cranes ≥80T set Crawler or Moblie Cranes ≥50T set Crawler or Mobile Cranes ≥25T set Vibration hammer machine 60KW set Bulldozer ≥110 HP set Excavator with bucket capacity ≥ 0.7m3 set Generator ≥ 200KVA set Welding machine set 10 Cutting machine set 10 Bending Machine set 10 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 Names of construction equipment Quantities Surface Vibration set 10 Rod Vibration D40-70 set 10 Concrete Bucket ≥1m3 set set Hydraulic Jack ≥60T set Mono Hydraulic Jack ≥24T set Prestressing cable Jack 250T-500T set Formwork of Super T Girder L=38.10 38.30 m set Formwork of Super T Girder L=28.70 m set Formwork of Voided Slab Girder - L=24 m set Formwork of Voided Slab Girder - L=21 m set Water pumping 60m3/h set 10 Formwork traveller for box girder bridge construction by balanced cantilever method set Gantry Crane 100T set Transformer Station ≥250KVA set Mortar 9m3/h 34/ 34 Unit Concrete Pumping machine PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE ... 250T-500T set Formwork of Super T Girder L=38.10 38.30 m set Formwork of Super T Girder L=28.70 m set Formwork of Voided Slab Girder - L=24 m set Formwork of Voided Slab Girder - L=21 m set Water pumping... on next PC cable and continue same sequence of prestressed as above mentioned • After pre-stressed all PC cable per girder, elevation of top of girder shall be surveyed at same locations of initial... KM 18+200 – KM 23+450 TABLE OF CONTENTS I PRESTRESSED CONCRETE II CONSTRUCTION METHOD FOR SUPER TEE GIRDERS III CONSTRUCTION METHOD FOR VOIDED SLAB GIRDERS 2/ 34 PHUONG THANH - QUYET TIEN - ANH