一、预应力桥梁施工预应力桥梁从施工程序上大致可分为处理路基，搭设支架、

A prestressed bridge construction <br>prestressing force from the handle construction procedure can be divided into the roadbed, the erection of the stent, the support stent provided camber, making installation template, preload bracket, mounting steel, corrugated pipe, steel cable, concrete, prestressed tension, duct grouting, sealing anchor, demolition, construction scaffold template such a step. <br>1, ground handling, erection bracket bearings and Camber bracket set: usually about to engage in ground handling covers the whole range of bridge construction across the width of the bridge. Thorough flat on the ground first of all to deal with the scope of bridge construction area, and rolled up to the required standard data. Then backfill ground elevation from the box beam bottom elevation of claim height, the elevation of each of the respective pier backfill predetermined high value, to ensure that the stent remains firmly in construction. After backfilling the foundation, excavation good drainage channels. Multi-layer structure using shaped brackets are arranged four-body products, stone and wood mat horizontal bottom and between the ground and leveling paved stone chips, between the steel support with the mast crisscross connecting up the interior of the outer steel pipes are made with scissors, Always, symmetrical oblique wire rope to be fixed, and the ribs of the box girder, the encryption diaphragm holder, in the cantilever plate number can be reduced appropriately. After the completion of the laying of the top frame bracket square timber, to further adjust the height of erection of the bracket, the bracket camber adjustment use, and then accurately detect the position of the center point of the carrier used in theodolite pier and to the platform, according to design requirements of the mounting bracket of FIG. . According camber formula: f = f1 + f2, the position of the beam cross-provided maximum, are assigned in the form of a parabola, after calculating camber value of each point on the stent by an adjustable screw base or jacking to further fine-tune the bottom mold. <br>2, making the mounting template, reinforced bracket mounting and preloading the bellows, strand: After complete bearing installation, in accordance with the drawing process and a predetermined size mounted box beam bottom template, a seam filling them sponge, disposed bracing presser foot. Before installation, requires careful examination template is not deformed or pollution, while ensuring compliance with the elevation of box girder design standards. After completion of the preload package unload sand, clean template brushing a releasing agent is measured again and elevation adjustment plate. After completion Scaffording, preloading the stent, a predetermined load is not less than 1.2 times the weight of the reinforced concrete beam body, to ensure that the load distribution is consistent with the casting box girder weight distribution, provision of adequate observation points, in strict accordance with three portions detachably loading requirements , squeeze time to ensure that, at each observation point during loading and unloading are to be observed to ensure that observations within a predetermined numerical technique, it can be considered substantially stable foundation settlement.<br>3, installation steel, corrugated pipe, concrete and strand: After adjusting plate, reinforced Anza twice accordance with the instructions, and then the bellows, the strand installation, after the completion of steel banding ribs. Steel, corrugated pipe, steel cable disposing of it into the concrete mixing, pouring and health sectors. The ingredients strict control, in accordance with the concrete mixture was stirred. Box twice pouring concrete, the floor, the ribs pouring concrete from low to high, a second layer of concrete from the middle to spread evenly on both sides to the design elevation by advancing a low to a high. Using plug-in vibrators vibrating compaction, mulching health. <br>4, duct grouting and prestressed tension: the design strength of the concrete strength of 95%, greater than 7 days of age and can be tensioned, under the protection of equipment without failure, tendon tension provided according to the design drawings tension tension stress sequence and for the detection process to cooperate with each other, serious operation and make relevant records. In order to avoid corrosion tendons, after prestressing, as early as possible duct grouting, cement grouting adopt provisions to ensure that age does not exceed, water-cement ratio compliance mud, cement slurry consistency suitable control. Grouting process should pay attention to the temperature and in strict accordance with operating procedures. <br>5, removal of the stent and anchor seal template: When the filling is completed, the exposed portion was washed anchor, the end face of the concrete steel banding cutting hair. After anchoring reinforcement steel mesh and spot welding integrally reservation, then install the template, pouring concrete, grouting the anchor seal, the strength to be 80% after grouting, disassembled roof support frame, in 90% strength grouting anchor seal and complete after removal of all brackets. When removing the holder from the start cross-symmetric uniformly to two detached, so that the weight bridge symmetrically evenly shared equally among the two supports, while simultaneously preventing the occurrence of cracks box girder due to uneven force.

First, pre-stressed bridge construction<br>Pre-stressed bridges can be broadly divided into treatment roadbeds from the construction procedures, set up brackets, mounts, bracket pre-archsetting settings, production installation templates, bracket pre-pressure, installation of steel, bellows, steel strands, concrete construction, pre-stressed pull, hole pulp, anchoring, demolition, bracket template such a construction step.<br>1, treatment of the foundation, set up bracket support and bracket pre-archsetting setting: the usual foundation treatment scope includes the upcoming construction of the bridge span and bridge width of the overall range. On the foundation treatment, the first step is to completely level the area of the construction bridge and crush it up to the prescribed data standard. Then backfilling the ground elevation from the box beam base elevation to the required height, backfilling bridge elevation each reached the corresponding high value, to ensure that the bracket in the construction remains firm. After the foundation is backfilled, the drainage channel is dug. Bracket more use four-body zigzag double structure arrangement, the bottom pad on the horizontal square stone wood and with the ground between the paving stone chips to level, between the bracket with steel pipe to cross the door frame, the inside and outside are used steel pipe as scissors support, at the same time to use the wire rope symmetrical pull to fix, and in the box beam ribs, cross-divider encryption bracket, At the cantilever plate, some can be reduced appropriately. After laying square wood on the top shelf, further adjust the height of the mounting bracket, adjust the pre-arching degree by using the upper support, and then accurately measure the center point position of the support with the meridian on the column and the table, and install the mount according to the design requirements. According to the pre-arching calculation formula: f-f1-f2, the beam's cross-middle position set the maximum value, according to the parabola form of distribution, calculate the pre-archvalue value of each point, through the adjustable wire rod top or base on the bracket to further fine-tune the bottom mold.<br>2, the production of installation template, bracket pre-pressing and installation of rebar, bellows, steel strands: after the completion of the mount installation, in accordance with the size of the drawings to process and install the box beam bottom template, template seam embedded sponge strip, set oblique support, pressure feet. Before installation, careful examination of the template for deformation or contamination, while ensuring that the height of the box beam sits conforms to the design standards. Remove the sandbag after the pre-pressure is complete, clean the template to paint the release agent, measure the elevation again and adjust the base plate. After the bracket is set up, the bracket is pre-pressured, the load regulation is not less than 1.2 times the weight of the beam reinforced concrete, to ensure that the load distribution is consistent with the weight distribution of the current pouring box beam, set up enough observation points, in strict accordance with the requirements of loading and unloading three times loading and unloading, pre-pressure time to ensure that each observation point in the process of adding and unloading to be observed, To ensure that the observation results are within the specified technical values, it can be considered that the foundation subsidence is basically stable.<br>3, the installation of rebar, bellows, steel strands and concrete construction: adjust the bottom plate, in accordance with the operating provisions of the reinforced steel twice, and then the bellows, steel strands installed, after completion of the rib plate steel. Rebar, bellows, steel strands are disposed of to enter the concrete mixing, pouring and health links. The ingredients are strictly controlled and stirred according to the ratio of the crucible. Box beam concrete is poured twice, the bottom plate, ribbed concrete is poured from low to high, the second layer of concrete from the middle to the two sides evenly paved to the design height, and from low to high. The use of plug-in vibrator stoicism, the use of covering health.<br>4, pre-stressed tensile and hole-way pressure pulp: concrete strength reached 95% of the design strength, and the age period is greater than 7 days after the tensile, in the case of ensuring that the equipment is not fault-free, the steel beam pull in accordance with the design drawings provided by the pull order and pull control stress, the detection process to cooperate with each other, serious operation and do a good job of the relevant records. In order to avoid pre-stressed rib rust, after applying pre-stress, as early as possible to carry out the hole-channel pulp, pulp using the specified cement, to ensure that the aging period is not exceeded, cement slurry than the standard, cement mud consistency control is appropriate. The temperature should be paid attention to during the pulping process and in strict accordance with the operating procedures.<br>5, anchor and bracket, template removal: when the grouting is completed, the exposed part of the anchor to clean, the end of the concrete chisel tied to the steel. Anchor after the steel mesh and reserved rebar spot welding, and then install the template, pouring concrete, pulp seal anchor, to be pressed to 80% of the strength, remove the top frame, in the pulp strength of 90% and after the completion of the anchor to remove all brackets. When removing the bracket, the weigh-in is evenly removed from the middle, so that the weight of the bridge is symmetrical, evenly borne by the two ends of the support average, while preventing the box beam due to uneven force cracks.

I. prestressed bridge construction<br>From the construction procedure, the prestressed bridge can be roughly divided into treatment of subgrade, erection of bracket, support, setting of bracket camber, fabrication and installation of formwork, pre pressing of bracket, installation of reinforcement, corrugated pipe, steel strand, concrete construction, pre-stressed tension, duct grouting, anchor sealing, removal and formwork of bracket.<br>1. Foundation treatment, support erection and pre camber setting of support: generally, the scope of foundation treatment includes the overall scope of bridge span and bridge width to be constructed. In the foundation treatment, first of all, the land area of the construction bridge shall be completely leveled and rolled to the specified data standard. Then the elevation of the backfill ground to the bottom of the box girder reaches the required height, and the elevation of the backfill pier reaches the corresponding specified high value, so as to ensure that the support remains firm in the construction. After the foundation is backfilled, the drainage channel shall be excavated. The supports are usually arranged in a four body double-layer structure, with horizontal square stone wood at the bottom and stone chips laid between the supports and the ground for leveling. Steel pipes are used between the supports to connect the portal frame vertically and horizontally. Steel pipes are used inside and outside as cross braces. At the same time, steel wire ropes are used to fix it symmetrically and diagonally, and supports are added at the ribs and diaphragms of the box girder, while those at the cantilever plate can be reduced appropriately. After the square timber is laid on the top bracket, the height of the bracket shall be further adjusted, and the camber shall be adjusted by the top bracket. Then, the center point of the support shall be accurately measured on the pier column and the abutment body with theodolite, and the support shall be installed according to the requirements of the design drawing. According to the calculation formula of camber: F = F1 + F2, the maximum value is set at the midspan position of the beam, which is distributed in the form of parabola. After the camber value of each point is calculated, the bottom formwork is further adjusted by the adjustable screw rod jacking or base on the support.<br>2. Fabrication and installation of formwork, pre pressing of support and installation of reinforcement, corrugated pipe and steel strand: after the installation of support, the formwork at the bottom of box girder shall be processed and installed according to the size specified in the drawing, and the formwork joints shall be embedded with sponge strips, and diagonal bracing and presser foot shall be set. Before installation, it is required to carefully check whether the formwork is deformed or polluted, and at the same time, ensure that the elevation of the box girder meets the requirements of the design standard. After preloading, remove the sand bag, clean the formwork and apply release agent, measure the elevation again and adjust the bottom plate. After the erection of the support, the support shall be preloaded. The load shall not be less than 1.2 times of the weight of the reinforced concrete of the beam body. The load distribution shall be consistent with the weight distribution of the cast-in-place box girder. Sufficient observation points shall be set. The loading and unloading shall be conducted in three times in strict accordance with the loading and unloading requirements. The preloading time shall be ensured. Each observation point shall be observed during the loading and unloading process to ensure that the observation results are within the specified technical values It can be considered that the foundation settlement is basically stable.<br>3. Installation of reinforcement, corrugated pipe, steel strand and concrete construction: after adjusting the bottom plate, install the reinforcement twice according to the operation regulations, then install the corrugated pipe and steel strand, and then bind the rib plate reinforcement. After the reinforcement, corrugated pipe and steel strand are disposed, they will enter into the concrete mixing, pouring and curing links. Strictly control the batching and mix according to the concrete mix proportion. The concrete of box girder is poured in two times, the concrete of bottom plate and rib plate is poured from low to high, the second layer of concrete is evenly spread from the middle to both sides to the design elevation, and is pushed from low to high. The immersion vibrator shall be used to vibrate and compact, and the cover curing shall be used.<br>4. Prestressed tensioning and duct grouting: after the concrete strength reaches 95% of the design strength and the age is more than 7 days, the tensioning can be carried out. Under the condition that the instrument and equipment are free of faults, the tensioning of steel strand shall be carried out according to the tensioning sequence and tensioning control stress provided in the design drawing. The testing process shall be coordinated with each other, operated carefully and recorded. In order to avoid the corrosion of prestressed reinforcement, the duct grouting shall be carried out as soon as possible after the application of prestress, and the specified cement shall be used for grouting to ensure that the age is not over, the water cement ratio of cement slurry reaches the standard, and the consistency of cement slurry is properly controlled. Pay attention to the temperature during the grouting process and strictly follow the operation procedures.<br>5. Removal of sealing anchor, support and formwork: after grouting, clean the exposed part of the anchorage and roughen the end face concrete to bind the reinforcement. After the anchor, the reinforcement mesh and the reserved reinforcement shall be spot welded together, then the formwork shall be installed, the concrete shall be poured, after the grouting and anchor sealing, after the grouting strength reaches 80%, the roof support shall be removed, and after the grouting strength reaches 90% and the anchor sealing is completed, all the supports shall be removed. When the support is removed, it shall be removed symmetrically from the middle of the span to both ends, so as to make the weight of the bridge body symmetrical and bear equally by the supports at both ends, and prevent the box girder from cracking due to uneven stress.<br>