后张法简支箱梁预应力施工工艺（The prestress construction technology of the post-tensioned box girder）.doc

后张法简支箱梁预应力施工工艺（The prestress construction technology of the post-tensioned box girder）The prestress construction technology of the post-tensioned box girderChina railway 19 bureau group fifth engineering co. LTD. Xinxiang girder fieldKeywords: three control, strength, elasto, age, control stress, tension, periodic calibration, periodic calibration, before useAbstract: after the construction of the prestress construction of the box girder with the latter, the required tensioning equipment includes oil pumps, jacks and 0.25 class anti-shock oil pressure meters. The raw materials are used in a 1 x 7-15.2-1860mpa type low relaxation steel strand. According to the process construction of prestressed construction process, pull rod, clear hole, steel strand processing and production, steel strand wire transfer and so on. The prestressing stress is performed in the three stages of pre-tensioning, the initial tension and the final tension, and the pre-tensioned three control: when the concrete reaches 35.5 MPa, the pre-tensioning can be carried out. When the strength meets the design requirements of 43.5 MPa, the initial tensioning can be carried out. According to the situation, the preliminary and early tensile can be carried out simultaneously, and the precast and the first tensioning can be carried out with the die tensioning. When the concrete strength reaches 53.5 MPa and the elastic modulus reaches 35.5 GPa, the age is greater than 10 days. During the tensioning process, the prestressed values are mainly based on the oil gauge reading, and the elongation value is supplemented, and the "three concentric, two synchronization" is achieved. Prestressed equipment to do: periodic verification (jack use more than 1 months or 200 times), regular calibration (hydraulic table by collision or oil leakage, oil pointer cannot be returned to the zero point) and before using the check (tensioning, determine if the hydraulic table and jack is properly matched; make jack empty 2-3 times, determine the jacks and hydraulic pipe works) to ensure the construction process, the equipment can work normally. At the time of zhang, a warning sign and a police cordon were set on both sides of the beam. After the tensioning, we must finish the work.1. Project overviewProject name xinxiang dongmeng jiangnu river bridge (DK600 + 908.36 DK618 + 309.20); Section name: new shijiazhuang to wuhan railway passenger line (henan section). Beam field precast beam is 32m, 24 m, and post - tensioned prestressed concrete mono-chamber box girder. 32m beam length 32.6 m, span 31.5 m; 24m beam length 24.6 m, span 23.5 m. Box girder cross section type for single room and simply supported box girder, beam body of C50 concrete strength design level, the high strength and low relaxation prestressed reinforcement steel strand and anchorage system using the anchor wire drawing system, pipe forming adopts pull rubber rod into the hole.Time limit for a project goal: plan on November 11, 2008 began construction beam field, on January 25, 2009, trial production, in full scale production on May 30, 2008, on April 30, 2010 complete box girder prefabrication, total duration 18 months.2. Tensioning equipment2.1 tensioning jackThe tensioning jack USES the YD2500/200 and YD3000/200 jacks produced by the four-flat Rio tinto prestressing machinery co., LTD. According to the tensioning value of the tensioning stage, the precast box girder adopts YD2500/200 jack, and the final stretch is adopted YD3000/200 jack.2.2 tensioning oil pumpThe oil pump is the ZB2 * 2/55 electric high pressure oil pump which is produced by the siping prestress machinery co., LTD.2.3 tensioning tablesThe tensioned oil pressure gauge is selected for the shockproof type. The beam field is selected with a 0.25-stage shock-proof oil meter. The maximum range of oil meters is 60MPa, with a minimum scale of 0.2mpa, and the dial diameter is 150mm. Once a month,It must be calibrated once a week.2.4 the anchor deviceWhen it is found that the steel cable slip, broken wire and clip are not meet the requirements, the anchor is used to anchor the strand wire.Check the prestressing equipment2.5.1 the prestressing equipment shall be accomplished: periodic verification, periodic calibration, and pre - review2.5.2 to ensure the accuracy of tension, the calibration of "oil pressure value and output force" of tensioning equipment is regularly carried out. The equipment and instruments used by the prestressed shall be used and managed by the specialists, and maintained and calibrated regularly. The jacks are calibrated with the pressure gauge to determine the relationship curve between tension and pressure gauge as the basis of tension. The jacks and oil meters shall be calibrated before use, or they shall not be used. When the jacks are calibrated with the pressure gauges, the calibration method of the top pressure test machine or pressure sensor should be adopted, and the amount of the external dew of the piston is approximately equal to the amount of exposure when the maximum load is tested. The dial reading of the pressure machine with the gauge of pressure gauge at all levels. Form a complete set of calibration data from linear regression, regression equation is: y = a + bx, linear regression correlation coefficient is not smaller than 0.9999, the coefficient of inspection is not greater than 1.05, and according to the load level at all levels under the load of said.2.5.3 the jacks should be checked in the following situations: first use after delivery; Serious oil leakage; Replacing oil pressure gauge with jack; The oil pressure gauge is subject to collision or malfunction, and the oil gauge pointer cannot be returned to zero; After each overhaul; The jack is used for more than 1 month or 200 times.3. Requirements and selection of raw materialsPrior to the purchase of raw materials, the qualified supplier shall be evaluated according to the requirements of ISO9000. The supplier must be in the qualified supplier directory. All raw materials shall be provided by the supplier with the factory inspection certificate, and shall strictly implement the entry inspection according to the relevant inspection items and batches.3.1 prestressed steel wiresThe 3.1.1 prestressed steel wire line is a low-slack steel wire with 1 x 7-15.2-1860mpa. According to the requirements of GB/T5224-2003 of prestressed concrete steel wire, the steel wire line manufacturer shall provide the elastic modulus of each batch line.3.1.2 steel wire shall be stored in a dry place to avoid dampness corrosion. The site is stored in a special area and is well covered in time by 200mm. Each batch of steel wire shall consist of the same batch number and the same strength of the steel strand.3.1.3 inspection of the steel winch: the surface quality of the steel strand shall not have cracks, spines and oil stains, and it shall not be allowed to have any pitting, which can be seen with rust or visible; There should not be broken, broken, and crossed wires; At the same time, the test chamber shall be inspected according to the requirements of the inspection approval, and the performance will be put into production after the performance is qualified.3.2 anchor and clip3.2.1 the anchor and fixture adopts the ym15-7, ym15-7, ym15-8 ym15-9, ym15-8, ym15-12 and the corresponding donor-j clips.3.5.2 shall be approved by the same manufacturer, the same variety, the same specifications, and the same number of anchors. When selecting the manufacturer for the first time, the inspection should be carried out on the appearance, the anchorage efficiency coefficient, the ultimate tensile strain, the anchor port friction, and the horn friction resistance. The appearance inspection of each batch of entry anchors shall be 10% of the total quantity, and no less than 10 sets. The appearance inspection shall have no cracks on the surface, and the dimensions shall conform to the design requirements.3.2.All the anchors shall be protected, stored and transported properly to avoid rust, stain, mechanical damage or loss. Temporary protective measures should not affect the effect of installation and the implementation of permanent anti-rust measures. Make a mark to prevent mixing. Verification requirements for metrological verification instruments: periodic verification, periodic calibration, pre-check.3.2.4 anchor, fixtures should be consistent with TB/T3193-2008 with the prestressed anchor, fixtures and connectors "the relevant provisions and the inspection qualified rear can use, the anchorage should be passed the provincial, ministerial appraisal, and meets the design requirements. The anchor plate shall be sealed and capped.3.2.5 the surface of the anchor and fixture shall have no crack, interlayer, burr, air bubble and rust, and the size shall conform to the design requirements and shall be deemed as qualified; Instead, double the number of tests should be taken. If there is still a set of non-conformance requirements, it should be tested and qualified.3.2.6 production such as found in some use of anchorage performance is bad (such as broken wire, slippery silk, shrank back) or doubt about the quality of the anchorage, shall be immediately to the anchorage of a performance test in turn according to the above requirements, because of poor quality may affect production or prestressed quality truly, a stable and reliable quality products (manufacturer) should be replaced.3.2.7 draw the rubber barAccording to economic planning institute of the ministry of railways issued "speed of 350 km railway passenger dedicated lines have a frantic jumble orbit after tensioning prestressed concrete simply supported box girder (double) drawings, can use pull pipe into the hole. This project adopts the suction rubber rod, the diameter of the rubber rod is 70mm, 80mm and 90mm respectively.Pull rubber bar shall comply with the interim technical conditions of passenger railway prestressed concrete precast beam iron technology 2004 no. 2004 provision: the rubber hose should be no surface crack, surface heat granule, rubber sponge. The trace length should not be greater than 3mm, the depth should not be greater than 1.5mm, and not more than one place per meter. The outer diameter deviation is plus or minus 4mm; The non-circular rate should be less than 20%; Hardness (shao's type A) is 65 plus or minus 5; The tensile strength is not less than 12Mpa, the elongation rate is not less than 350%, and the stretching strength of 300% is not less than 6Mpa.4. Prestressed construction process4.1 prestress construction processPrestressed construction process flow chart4.2 construction operation key points4.2.1 production and wearing of steel strandBlanking and weaving beam: yard ground flat steel strand, the grinding wheel cutting machine cutting, weaving beam with 22, binding wire, spacing of 1.5 m, should first when weaving beam steel strand with comb carrige straighten out, and try to make each root steel strand tightness. The length of material under the steel wire is equal to the length of the design and 1640mm. The steel bundles are strictly according to the length of the construction drawing.Beam method: a 3t winder is used, and the front of the steel beam is equipped with a bundle ring and a traction head. The ring is made of seamless steel tube, phi 70mm. Drawing head conical, front end with TAB which will end when using the end wear into the lantern ring of steel strand, pulling out from thimble steel strand the middle, make steel strand and socket set of tight, USES the winch to pull TAB to wear line traction head.Construction technical requirements: the steel cable shall be kept dry and clean, and the steel cable shall be no less than 20cm from the ground.Add cover to prevent rain and oil erosion. The opening is drawn by winch, measured by steel ruler. The material is cut by grinding machine, it is strictly forbidden that the steel strand is damaged by spark, and the end of the steel cable is bound tightly with wire to avoid the loose. Every beam of steel, as far as possible, USES the steel strand on the same plate to achieve the same mechanical properties, so as to avoid the phenomenon that the elastic modulus is not equal to each other. If encounter in different cases to use different batches of steel strand, the two batch of steel strand of the difference of the modulus of elasticity to between 0.02 GPa (when calculating the average of the two batches of steel strand elastic modulus), if does not meet the above conditions, are not allowed to use. Straighter, and tie the thread at each interval of 1.5 m to tie together, make the bundle straight and untwisting. When the steel strand is classified according to the number, the distance of the fulcrum shall be no greater than 3m and the end of the cable shall be 1.5m.During transportation, the minimum bending radius must not be less than 1m. To hole in beam method can adopt the method of human push, when wearing a bouquet of difficulties, the channel prior to wear beam with a through hole opener by again all the way, in order to make sure on the steel beam, and check the channel and the serial number of the steel beam. The drag direction and the direction of the steel beam are perpendicular to the anchor pad.When the steel wire is inserted, the exposed part should be sealed with canvas bag to prevent water and water from damming and rusting.4.2.2 prestressed tensioningPreliminary applied stress at both ends on both sides of the four symmetric tensioning jack at the same time, according to the test when tensioning pipe friction and friction test data, a circle to adjust the tension, the tension and the double control elongation indicators, tension to tension control is given priority to, with steel beam elongation for checking.4.2.3 steel strand cutting and process handoverAfter completing 24h, zhang drew the check to confirm the non-slip wire phenomenon and check the retracting of the steel wire, the cutting of the steel wire head can be carried out in accordance with the requirement, and the cutting distance is 35 45mm from the surface of the anchor. Steel strand cutting is cut with grinding wheel saws. After the steel strand is cut and the process is transferred, the next process (grouting) construction can be carried out.5. Prestress tensioning process5.1 conditions for the prestressed concrete tensioning process to begin operation5.1.1 materials and accessories have been tested and confirmed.5.1.2 the equipment is in good condition.5.1.3 the measuring instrument has been calibrated (including self - school) and within the validity period.5.1.4 receive a note from the technical department of beam field technology departm