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
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1、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, te
2、nsion, 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
3、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
4、, 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 prelimi
5、nary 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 pre
6、stressed 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 colli
7、sion 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
8、 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 r
9、ailway 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, bea
10、m 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 constr
11、uction 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 fo
12、ur-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
13、 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 d
14、iameter 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
15、 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 manage
16、d 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
17、 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 pre
18、ssure 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 accordin
19、g 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 cann
20、ot 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 quali
21、fied 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-sla
22、ck 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 sto
23、red 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 shal
24、l 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 t
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