CN115305836A - Bridge stay cable lag tensioning construction process - Google Patents

Abstract

The invention relates to the field of constructional engineering, in particular to a construction process for lagging and tensioning a stay cable of a bridge, which comprises the following steps: a) Mounting a hanging basket; b) Prepressing the hanging basket; c) Mounting a bottom die and an outer die, mounting a steel bar in a prestressed manner, and mounting a similar template; d) Pouring and maintaining concrete; e) Stretching the three-way prestressed tendons; f) Grouting and sealing the anchor; g) The next section of forward construction of the hanging basket; h) Although the stress of the main beam is different from the original process in the bridge forming state, the tension force of the stay cable is not changed correspondingly, the stress in the bridge forming state is basically the same as the original process, and the construction progress is accelerated compared with the original process.

Description

A Construction Technology of Bridge Stay Cable Lag Tension

technical field

The invention relates to the technical field of construction engineering, in particular to a bridge stay cable hysteresis tensioning construction technology.

Background technique

With the progress of urbanization in my country and the acceleration of traffic construction, domestic bridge construction has also entered a new stage of development. Large-scale cross-river and cross-river bridge projects continue to appear. Segmental beams, longitudinal prestressing in the tension box, cable stay installation, and hanging basket moving forward to the next section. After the stay cable is installed, the hanging basket is moved forward to the next section, which is easily affected by the stay cable , it is more difficult to move the hanging basket forward, so the construction time is longer. In order to speed up the construction progress, a construction technology of lagging tension of the cable is proposed.

Contents of the invention

The object of the present invention is to provide a bridge stay cable hysteresis tensioning construction process which can speed up the construction progress.

To achieve the above object, the technical scheme of the present invention is as follows:

A kind of bridge stay cable hysteresis stretching construction technology, it is characterized in that: described construction technology step is as follows: a), install hanging basket; b), hang basket preload; Stress installation, similar formwork installation; d), concrete pouring and maintenance; e), tensioning three-way prestressed beams; f), grouting, anchor sealing; g), the next section of the hanging basket moving forward construction; h ), the beam ends are installed with stay cables for tensioning.

Preferably, in the step a), all structural parts of the hanging basket in the installation of the hanging basket are installed by tower cranes and crawler cranes, and the main girder is assembled on the ground and hoisted as a whole, and then the bottom basket system and the side system are installed; the specific steps are: Track system installation, overall hoisting after splicing the main truss system on the ground, installation of anchor system, installation of front upper beam, installation of hanging basket front and rear suspension, installation of hanging basket bottom basket system, installation of hanging basket platform system, installation of hanging basket hydraulic system .

Preferably, the step b), the loading method of the preloading of the hanging basket is to divide the loading into four times: 0%, 80%, 100%, and 110%. After each loading, the hanging basket is subjected to settlement observation. When the average settlement of 24h is less than 2mm, the next loading is carried out, and the last level of stabilization time is 72 hours. If the settlement is not stable, the preload should be continued until the bracket deformation tends to be stable and stop;

The loading sequence is from the center of the pier to both sides, from near to far, front to back, left to right, symmetrically, and the bottom plate and web are first ballasted;

The pre-compression measuring points are arranged at the main truss, guide beam, front and rear lower beams, and longitudinal beams;

The observation method is to carry out elevation measurement before preloading, step-by-step loading, and after all preloading loads are loaded and unloaded, and record the measurement results of all the above measuring points, and calculate their elastic deformation, that is, measure the measuring points before loading Elevation, as the initial data, after the stage loading is completed, the settlement of the support should be monitored every 12 hours. When the average settlement difference of the support measuring points for 12 hours is less than 2mm, the next stage of loading can be carried out. When the loading is 110% If the average settlement of the adjacent 24 hours is less than 1mm or the average settlement of each monitoring point for the first 72 hours is less than 5mm, it can be unloaded. When unloading, it should be unloaded symmetrically on both sides. The order of unloading is opposite to that of loading. , after loading, unload first, observe once after unloading is completed, observe the elevation of each measuring point after unloading 6h, preloading time is not less than three days, after preloading is completed, calculate the elastic and non-elastic deformation values of the hanging basket according to the obtained data, The calculation formula is: inelastic deformation value = height before loading - height after unloading, elastic deformation value = height after unloading - height before unloading;

After the loading is complete, after confirming that the hanging basket is stable and completing various data observations, it can be unloaded.

Preferably, the step g), the next section of the construction of the hanging basket moving forward, is to carry out the hanging basket walking, the hanging basket is walking for the first time or the track is designed to be used in reverse, it is necessary to accurately measure and release the hanging basket forward track position, Lay or reverse the track pad beam and track according to the design drawings. If the track needs to be extended, use bolts and two connecting plates to connect the two tracks into a whole, use the vertical fine-tie rebar of the box girder, and anchor the track through the track pressure beam , complete the track installation, ensure that the top surface of the track is level, move the track forward and place it in place, and then lower the jack slowly so that the front support acts on the track to complete the track forward operation, and then install a crane on both sides of the parallel truss The rod hangs the rear lower beam, and the suspender pad beams on both sides of the parallel truss should be temporarily spot-welded on the lower or upper flat rod of the parallel truss, and then remove the suspenders on the other rear lower beams anchored on the box girder At the same time, the lower crossbeam of the bottom basket is suspended on the sliding guide beam on the side formwork with wire ropes and gourds for protection, and the screw jack is used to slowly loosen the rear anchor rod of the main truss on the rear anchor beam, so that the buckle pulley buckles the track, and reverse After the pulley is fully stressed, retract the jack, loosen the rear anchor rod, remove the rear anchor rod in the rear end platform of the outer sliding beam and the box, and then install a pad beam at the front end of the track, and pass a piece of fine-rolled steel through the pad beam to the front support. Install a through-type jack at the rear end of the front support, use a nut to connect with the precision-rolled steel, and connect the jack to the oil pump at the same time;

Finally, carry out the walking of the hanging basket. When walking on the hanging basket, it is necessary to keep the main truss moving forward synchronously. After the front pressure beam is removed and the main truss is moved forward, wait until the reserved holes in the box chamber of the lower beam and the rear anchor are aligned with the beam spreader and the rear anchor node box, and then immediately anchor the rear anchor point of the hanging basket, and then After installing the bottom basket boom and wing boom, loosen the boom after walking, adjust the position and elevation of the formwork, then move the rolling spreader to the reserved hole, put the boom again, and wait for the next walk.

Preferably, the step c), bottom formwork, external formwork installation, reinforcement prestressed installation, similar formwork installation;

Preferably, the concrete in d), concrete pouring and curing adopts centralized mixing, and the two cantilever ends are poured symmetrically, and the webs on both sides of the same cantilever are also poured symmetrically, and the unbalanced weight of the concrete in the warehouse must not exceed 1% of the weight of the beam section. /4. When pouring concrete, the bottom plate, the rear web, and then the top plate should be poured first, and the sequence of pouring concrete symmetrically to the front, rear, and two webs should be followed.

Preferably, said e), the tensioning three-way prestressed beam is to arrange longitudinal, horizontal and vertical steel beams, and the prestressed steel beams are all steel strands, and the steel strands are low-relaxation high-strength prestressed steel strands, and the control Stress is double controlled by tensile stress and elongation, and it should be symmetrically and evenly stretched during tension;

Tensioning sequence: longitudinal prestressed beam→transverse prestressed beam, diaphragm prestressed beam with cable area→vertical prestressed beam, vertical prestressed beam lags behind one beam section tension, box girder roof cantilever twice Tensile prestress and vertical prestress adopt low retraction secondary tension prestress anchor system.

Preferably, said d), concrete pouring and maintenance are covered and sprinkled for maintenance; said step f), grouting, and anchor sealing adopt a secondary slurry collection process, and after the slurry collection and plastering is completed, immediately use geotextiles to cover, Sprinkle water on the top of the geotextile to keep it moisturized. Both the web and the bottom plate are sprinkled with water for curing. After the prestressed tension and grouting are completed, when the hanging basket moves forward, the formwork is removed. The curing time should not be less than 7 days.

Advantages of the present invention: By changing the construction process, the present invention changes the installation order of the cable stays in the construction sequence of the general suspension cast section of the bridge. It is more difficult to move the basket forward. Through the installation steps and structural characteristics of the hanging basket, the stress of the bridge after the lagging of the cables is guaranteed to be within a safe range. Although the stress of the main girder in the bridge state is different from the original process, the There is no corresponding change in tension cable force, so that the stress in the bridge state is basically the same as the original process, and the construction progress is accelerated compared with the original process.

Description of drawings

Fig. 1 is the overall construction process flow chart of the present embodiment.

Fig. 2 is a flow chart of the suspension casting construction process of the hanging basket in this embodiment.

Fig. 3 is the installation and construction process flow of the hanging basket in this embodiment.

Fig. 4 is a comparison diagram of the original process of this embodiment and the hysteresis tensioning process of the stay cables.

Fig. 5 is a diagram of the calculation results of the maximum and minimum stresses after the beam section is moved to the hanging basket in this embodiment.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings.

Example 1

As shown in Fig. 1-3, a kind of bridge stay cable hysteresis stretching construction process, described construction process steps are as follows: a), installation hanging basket; b), hanging basket preloading; c), bottom formwork, outer formwork Installation, steel prestressed installation, similar formwork installation; d), concrete pouring and maintenance; e), tensioning three-way prestressed beams; f), grouting, anchor sealing; g), hanging basket forward construction next step Segment; h), the beam ends are installed with stay cables for tension.

Preferably, in the step a), all structural parts of the hanging basket in the installation of the hanging basket are installed by tower cranes and crawler cranes, and the main girder is assembled on the ground and hoisted as a whole, and then the bottom basket system and the side system are installed; the specific steps are: Track system installation, overall hoisting after splicing the main truss system on the ground, installation of anchor system, installation of front upper beam, installation of hanging basket front and rear suspension, installation of hanging basket bottom basket system, installation of hanging basket platform system, installation of hanging basket hydraulic system .

Preferably, the step b), the loading method of the preloading of the hanging basket is to divide the loading into four times: 0%, 80%, 100%, and 110%. After each loading, the hanging basket is subjected to settlement observation. When the average settlement of 24h is less than 2mm, the next loading is carried out, and the last level of stabilization time is 72 hours. If the settlement is not stable, the preload should be continued until the bracket deformation tends to be stable and stop;

The loading sequence is from the center of the pier to both sides, from near to far, front to back, left to right, symmetrically, and the bottom plate and web are first ballasted;

The pre-compression measuring points are arranged at the main truss, guide beam, front and rear lower beams, and longitudinal beams;

The observation method is to carry out elevation measurement before preloading, step-by-step loading, and after all preloading loads are loaded and unloaded, and record the measurement results of all the above measuring points, and calculate their elastic deformation, that is, measure the measuring points before loading Elevation, as the initial data, after the stage loading is completed, the settlement of the support should be monitored every 12 hours. When the average settlement difference of the support measuring points for 12 hours is less than 2mm, the next stage of loading can be carried out. When the loading is 110% If the average settlement of the adjacent 24 hours is less than 1mm or the average settlement of each monitoring point for the first 72 hours is less than 5mm, it can be unloaded. When unloading, it should be unloaded symmetrically on both sides. The order of unloading is opposite to that of loading. , after loading, unload first, observe once after unloading is completed, observe the elevation of each measuring point after unloading 6h, preloading time is not less than three days, after preloading is completed, calculate the elastic and non-elastic deformation values of the hanging basket according to the obtained data, The calculation formula is: inelastic deformation value = height before loading - height after unloading, elastic deformation value = height after unloading - height before unloading;

After the loading is complete, after confirming that the hanging basket is stable and completing various data observations, it can be unloaded.

Preferably, the step g), the next section of the construction of the hanging basket moving forward, is to carry out the hanging basket walking, the hanging basket is walking for the first time or the track is designed to be used in reverse, it is necessary to accurately measure and release the hanging basket forward track position, Lay or reverse the track pad beam and track according to the design drawings. If the track needs to be extended, use bolts and two connecting plates to connect the two tracks into a whole, use the vertical fine-tie rebar of the box girder, and anchor the track through the track pressure beam , complete the track installation, ensure that the top surface of the track is level, move the track forward and place it in place, and then lower the jack slowly so that the front support acts on the track to complete the track forward operation, and then install a crane on both sides of the parallel truss The rod hangs the rear lower beam, and the suspender pad beams on both sides of the parallel truss should be temporarily spot-welded on the lower or upper flat rod of the parallel truss, and then remove the suspenders on the other rear lower beams anchored on the box girder At the same time, the lower crossbeam of the bottom basket is suspended on the sliding guide beam on the side formwork with wire ropes and gourds for protection, and the screw jack is used to slowly loosen the rear anchor rod of the main truss on the rear anchor beam, so that the buckle pulley buckles the track, and reverse After the pulley is fully stressed, retract the jack, loosen the rear anchor rod, remove the rear anchor rod in the rear end platform of the outer sliding beam and the box, and then install a pad beam at the front end of the track, and pass a piece of fine-rolled steel through the pad beam to the front support. Install a through-type jack at the rear end of the front support, use a nut to connect with the precision-rolled steel, and connect the jack to the oil pump at the same time;

Finally, carry out the walking of the hanging basket. When walking on the hanging basket, it is necessary to keep the main truss moving forward synchronously. After the front pressure beam is removed and the main truss is moved forward, wait until the reserved holes in the box chamber of the lower beam and the rear anchor are aligned with the beam spreader and the rear anchor node box, and then immediately anchor the rear anchor point of the hanging basket, and then After installing the bottom basket boom and wing boom, loosen the boom after walking, adjust the position and elevation of the formwork, then move the rolling spreader to the reserved hole, put the boom again, and wait for the next walk.

Preferably, the step c), bottom formwork, external formwork installation, reinforcement prestressed installation, similar formwork installation;

Preferably, the concrete in d), concrete pouring and curing adopts centralized mixing, and the two cantilever ends are poured symmetrically, and the webs on both sides of the same cantilever are also poured symmetrically, and the unbalanced weight of the concrete in the warehouse must not exceed 1% of the weight of the beam section. /4. When pouring concrete, the bottom plate, the rear web, and then the top plate should be poured first, and the sequence of pouring concrete symmetrically to the front, rear, and two webs should be followed.

Preferably, said e), the tensioning three-way prestressed beam is to arrange longitudinal, horizontal and vertical steel beams, and the prestressed steel beams are all steel strands, and the steel strands are low-relaxation high-strength prestressed steel strands, and the control Stress is double controlled by tensile stress and elongation, and it should be symmetrically and evenly stretched during tension;

Tensioning sequence: longitudinal prestressed beam→transverse prestressed beam, diaphragm prestressed beam with cable area→vertical prestressed beam, vertical prestressed beam lags behind one beam section tension, box girder roof cantilever twice Tensile prestress and vertical prestress adopt low retraction secondary tension prestress anchor system.

Preferably, said d), concrete pouring and maintenance are covered and sprinkled for maintenance; said step f), grouting, and anchor sealing adopt a secondary slurry collection process, and after the slurry collection and plastering is completed, immediately use geotextiles to cover, Sprinkle water on the top of the geotextile to keep it moist. Both the web and the bottom plate are sprinkled with water for maintenance. After the prestressed tension and grouting are completed, the formwork is removed when the hanging basket moves forward. The curing time shall not be less than 7 days.

In this embodiment, there are 17 segments (1~17#) in the cantilever casting of the main girder box girder, and the segments consist of (3×3.5+14×4) m. The main truss of the hanging basket is assembled in the back field. After the 0# block is poured, use the tower crane to hoist the hanging basket rods, and assemble the hanging basket above the 0# block. After the hanging basket is assembled, pre-press and record the deformation, and install the bottom form , Outer formwork, tying steel bars, installation of inner formwork, symmetrical pouring of 1~17# beam sections.

The stay cables are installed synchronously in the pouring 4~15# beam section, and the cable force is adjusted according to the construction monitoring on site. Cantilever casting of 15# beam section, installation of stay cables is completed.

In this embodiment: the hanging basket is composed of a main truss system, a walking system, an anchoring system, a suspension system, a bottom basket system, a formwork system and an operating platform protection system; the main truss system is the main force-bearing component of the hanging basket, and is composed of The rhombus truss, pin shaft, horizontal parallel truss, front upper beam and other components, the rhombus truss is composed of force-bearing members and boxes with pins, which is easy to disassemble and transport, and the rhombus truss is vertically placed on the web of the box girder , two trusses are used, and the two trusses are connected horizontally through parallel trusses to form a whole. The front upper beam is erected on the front node of the diamond-shaped truss, and a lifting point is set on it, which is used as the suspension bottom basket system and the sliding beam of the inner and outer molds. The beam is at the same time It plays the role of connecting the main trusses into a whole. The main truss system is composed of 3 rhombus-shaped main trusses and horizontal connecting systems. 3 The center distance of the main truss is 8.4/8.6m, the center height is 3.5m, the distance between the front and rear nodes of each truss is 4.2m, and the total length is 12.2m. The main member of the truss adopts a lattice structure welded by []40a channel steel, and the nodes are connected by pins through the box. The horizontal connection system is welded by []14 channel steel, and it is set on the vertical rods of the two main trusses. Its function is to ensure the lateral stability of the main truss, and to suspend the rear beam of the bottom formwork platform in the running state. The main truss of the hanging basket adopts steel pads to adjust the level to ensure that the main truss is vertical;

The walking system is mainly composed of walking track, sliding seat, hanging roller, track pressure beam, track pad beam and other parts. The track is mainly used for the forward movement of the hanging basket without load. When the hanging basket moves forward, the main jack lifts the front support, the sliding seat is disengaged from the track, the whole track is dragged forward and then anchored, then the hanging rollers are reversed on the track, and the main truss is placed on the track under the front support Finally, two 32t hydraulic jacks are used as power. When walking, one end of a longer Φ32mm fine-rolled rebar is anchored to the front end of the track, and the other end is anchored to the 32t jack at the front fulcrum of the hanging basket. Oil is supplied by an electric oil pump, and the jack pushes forward The sliding of the fulcrum drives the entire hanging basket to move forward. After reaching a stroke, the hydraulic pump returns oil, and the cycle is repeated until it is pushed to the anchoring position;

Among them, the anchorage system is the self-anchor balancing device of the main truss system, which is composed of pole beams, precision-rolled rebar, connector nuts, pads and other parts. When the hanging basket is pouring concrete, the rear end uses Φ32mm fine-rolled threaded steel bar (coated with PVC protection pipe) to pass through the pre-buried hole and pull it on the top plate of the poured beam section. The rear anchor beam adopts double channel steel, single-piece diamond 3 rear anchor beams and 6 rear anchor suspenders are installed in the frame, and the rear anchor suspenders are anchored through the pre-embedded fine-rolled threaded steel bars on the side webs of the beams and the reserved holes on the top plate. Ensure that the rear anchor rod bears vertical force.

Among them, the bottom basket system directly bears the concrete weight of the beam section, and provides an operating site for forming forms, steel bar binding, concrete pouring and other processes. It consists of bottom formwork, longitudinal beams and front and rear beams, and the bottom formwork adopts large steel formwork. Among them, the longitudinal beam is made of H350×175 steel, and the front and rear lower beams are assembled and welded with 2HN400×200 steel. The distance between the centers of the front and rear beams is 5.5m. The longitudinal beams are connected to the beams with bolts;

Among them, the suspension system is used to suspend the bottom mold platform and the outer mold. And transfer the self-weight of the bottom formwork platform, side formwork, beam section concrete weight and other construction loads to the main frame and the finished beam section. The suspension system includes the front upper beam, the front and rear suspenders of the bottom form platform, the front and rear suspenders of the side form guide beam, the slideway beam suspender, the pad beam, the pole beam and the screw jack.

The formwork system is mainly composed of four parts: outer mold, inner mold, bottom mold and end mold. The outer formwork is a steel formwork, which is composed of panels, transverse ribs, vertical ribs and skeletons. The formwork is processed in blocks according to the box girder structure and connected by bolts. Skeleton and formwork are generally transported separately and assembled on site. The bottom formwork is composed of panels and transverse ribs, and the formwork is processed in blocks according to the box girder structure and connected by bolts.

The construction platform is divided into bottom construction platform, side form work platform and bottom form front work platform. The bottom construction platform is mainly used for the disassembly and assembly of the bottom anchor and the concrete surface treatment of the bottom surface of the box girder, and is located at the rear of the bottom formwork. The side working platform is mainly used to disassemble the side concrete and the sliding beam suspension wheel, and is located at both ends of the bottom form. The working platform in front of the bottom mold is mainly used for sealing and tensioning the front end of the box girder, and is located at the front of the bottom mold.

The overall construction is:

Step 1: The construction of the lower structure of the main bridge and Block 0 is completed;

Step 2: After the construction of Block 0 is completed, install the hanging basket.

Step 3: (1) Utilize the hanging basket to hang and pour the No. 1 block symmetrically; (2) Tension the prestressed force of the No. 1 block; (3) Move the hanging basket forward; (4) Repeat steps 1 to 3 to complete the No. 2 to 3 blocks pouring;

Step 4: (1) Utilize the hanging basket to cast No. 4 block symmetrically; (2) Stretch the prestress of No. 4 block; (3) Erect and stretch the stay cable; (4) Move the hanging basket forward; (5) Repeat Steps 1 to 4, complete the tensioning of blocks No. 5 to No. 15 and stay cables; (6) Set up the support of the cast-in-place section of the side span;

Step 5: (1) Use the hanging basket to symmetrically cast No. 16 and No. 17 blocks; (2) Stretch the corresponding prestress; (3) Use the bracket method to complete the cast-in-place section of the side span;

Step 6: (1) Close up according to the principle of side span first, then middle span; (2) Remove part of the side span support of 12# pier so that the side span side hanging basket formwork enters, and the 13# pier hanging basket moves forward 2m to the 18# beam section , the side-span hanging basket suspender intersects the 19# beam section by 50cm, and stops moving forward; (3) After the hanging basket is in place, install the suspender, and then install the side-span closing section formwork and steel bars, at the cantilever ends on both sides of 13# ( 17# end of the beam section) to place a re-weighting water tank, and add water to the weight of 54 tons; (4) Continuously measure the closing section, lock the closing section with strength during the low temperature period of the day, pour concrete, and unload and change the weight in the same amount as the concrete is being poured ( The middle span side is not unloaded), after the concrete reaches the qualified strength, stretch the prestressed steel tendons of part of the side span closing section, remove the stiff skeleton, and stretch all the prestressed steel tendons of the side span closing section according to the design; (5) Remove the side span Bracket and 13# pier hanging basket; (6) During the construction of the side span closure section of No. 12 pier, the buckle support is used to construct the side span closure section of No. 15 pier at the same time;

Step 7: (1) The main span closure adopts the hanging method, the hanging basket is returned to the main pier for removal, and a 3000KN jacking force is applied longitudinally before the mid-span closure; (2) Formwork and steel bars are installed at the mid-span closure section; (3) The mid-span closure The section beam section (the end of the 17# beam section) is placed to replace the heavy water tank, and the water weight of No. 13 and No. 14 piers is 54 tons;

(4) Continuously measure the closing section, lock the closing section with a stiff skeleton during the low temperature period of the day, pour concrete, and unload and change weight in equal amounts while pouring concrete; (5) After the concrete reaches the qualified strength, first partially stretch the prestress For steel tendons, remove the rigid frame and stretch all the mid-span closed steel tendons for prestress according to the design;

Step 8: Construction of bridge deck system.

Through the above process, the construction period is saved. The original tensioning condition of No. n stay cables is carried out after the prestressed tensioning condition of No. n beam section and before the No. After the No. 1 beam section is moved to the hanging basket, it is carried out before the concrete pouring of the n+1 beam section, that is, the lagging tension construction process of the bridge stay cable. Taking the No. 4 beam section and the No. 5 beam section as examples, the original process and The hysteresis tensioning process of the stay cables is shown in Figure 4.

In this calculation and analysis, the tension timing of the stay cables has changed, but the tension of the stay cables remains unchanged;

In the construction process of the standard beam section, when the stay cables are stretched behind, the most unfavorable working condition is the working condition after each beam section is moved to the hanging basket. The maximum and minimum stress calculation results of No. 5 to No. 16 beam sections after moving the hanging basket are shown in the table of attached drawing 5. It can be seen from the table that the maximum tensile stress of each working condition is 0.1MPa, and the maximum compressive stress is 13.6MPa. During the construction process Main girder stress safety;

From the above calculation results, it can be seen that it is feasible to change the tensioning timing of the stay cables of the nth beam section to after the n+1 beam section is moved to the hanging basket, and the stress of the main girder is safe during the construction process.

Although the stress of the main girder in the completed bridge state is different from the original process, the stress in the completed bridge state can be basically the same as the original process by changing the tension force of the stay cables accordingly.

Therefore, after the steps of the present invention are changed, the construction period is accelerated without affecting the safety of the bridge.

The above is a detailed description of the present invention in conjunction with specific embodiments, and it cannot be assumed that the specific embodiments of the present invention are limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, several equivalent substitutions or obvious modifications are made without departing from the concept of the present invention, and the performance or use is the same, all should be regarded as belonging to the present invention by the submitted claims The scope of patent protection determined by the book.

Claims (7)

1. A bridge stay cable lag tensioning construction process is characterized in that: the construction process comprises the following steps:

a) Mounting a hanging basket; b) Prepressing the hanging basket; c) Mounting a bottom die and an outer die, mounting a steel bar in a prestressed manner, and mounting a similar template; d) Pouring and maintaining concrete; e) Stretching the three-way prestressed tendons; f) Grouting and sealing the anchor; g) The next section of forward construction of the hanging basket; h) And the beam end is provided with a stay cable for tensioning.

2. The bridge stay cable lag tensioning construction process according to claim 1, characterized in that: step a), mounting all structural members of a hanging basket in the hanging basket by using a tower crane and a crawler crane, integrally hoisting a main truss after the main truss is integrally assembled on the ground, and then mounting a bottom basket system and a side system; the method comprises the following specific steps: the method comprises the following steps of installing a track system, integrally hoisting the main truss system after splicing the main truss system on the ground, installing an anchoring system, installing a front upper crossbeam, installing a front suspension and a rear suspension of a cradle, installing a bottom basket system of the cradle, installing a cradle platform system and installing a cradle hydraulic system.

3. The bridge stay cable lag tensioning construction process according to claim 1, characterized in that: the loading mode of the step b) and the hanging basket prepressing is to divide the loading into four times: 0%, 80%, 100% and 110%, after each loading, carrying out settlement observation on the hanging basket, carrying out next loading when the average value of the settlement amount of 24 hours is less than 2mm, wherein the last stage of stabilization time is 72 hours, and if the settlement is not stable, continuing to carry out load pre-pressing until the deformation of the bracket tends to be stable and stops;

the loading sequence is that the loading is carried out from the center of the pier to two sides in sequence, and the loading is carried out from near to far, front to back and left to right symmetrically, and a bottom plate and a web plate are ballasted firstly;

the pre-pressing measuring points are arranged at the main truss, the guide beam, the front and rear lower cross beams and the longitudinal beam;

the observation method comprises the steps of carrying out elevation measurement before prepressing, step loading, after all loading of prepressing load and after unloading, recognizing and recording measurement results of all the measuring points, and calculating elastic deformation of the measurement results, namely measuring the elevation of the measuring points before loading to serve as initial data, monitoring the settlement of the support at intervals of 12 hours after step loading is finished, carrying out next-stage loading when the average value of the settlement difference of 12 hours of the measuring points of the support is smaller than 2mm, carrying out unloading when the average value of the settlement of 24 hours adjacent to each other after 110% of loading is smaller than 1mm or the average value of the settlement of the initial 72 hours of each monitoring point is smaller than 5mm, carrying out bilateral symmetry unloading when unloading is carried out, wherein the unloading sequence is opposite to the loading sequence, the first-stage unloading is carried out, the second-stage loading is carried out, the first-stage unloading is carried out after the second-stage loading is carried out, the elevation of each measuring point is observed once after the unloading is carried out for 6 hours, and after the prepressing is finished, calculating the elastic and inelastic values of the cradle according to the obtained data, and calculating formula is as follows: the inelastic deformation value = elevation before loading-elevation after unloading, and the elastic deformation value = elevation after unloading-elevation before unloading;

after the loading is finished, unloading can be carried out after the cradle is confirmed to be stable and various data observation is finished.

4. The bridge stay cable lag tensioning construction process according to claim 1, characterized in that: step g) the next section of the forward movement construction of the hanging basket, namely, the hanging basket is moved for the first time or the rail is designed to be used in a front-back reversing way, the position of the forward movement rail of the hanging basket needs to be accurately measured, a rail pad beam and the rail need to be laid or reversed according to the design drawing, the rail needs to be lengthened, the two rails are connected into a whole by using bolts and two connecting plates, the rail is anchored by using the vertical fine-rolled thread steel of a box girder and a rail pressing beam, the rail installation is completed, the rail ensures the top surface to be horizontal, a jack is slowly placed after the rail is moved forward in place, a front support is acted on the rail to complete the forward movement operation of the rail, then, 1 suspender is respectively arranged at the two sides of the parallel truss to suspend a rear lower cross beam, the suspension rod pad beams on two sides of the flat coupling are temporarily spot-welded on a lower flat rod or an upper flat rod of a flat coupling truss, then suspension rods anchored on other rear lower cross beams on a box girder are removed, a bottom basket rear lower cross beam is simultaneously suspended on a sliding guide beam on a side mold by using a steel wire rope and a hoist for protection, a main truss rear anchor rod is slowly loosened on a rear anchor pressing beam by using a screw jack, a left-hand fastening wheel fastens a track, the jack is withdrawn after the left-hand fastening wheel is completely stressed, the rear anchor rod is loosened, the rear anchor rod is removed in a platform at the rear end of an outer sliding beam and a box, then a pad beam is installed at the front end of the track, a piece of precision steel is threaded through the pad beam to a front support, a through type jack is installed at the rear end of the front support, the through type jack is connected with the precision steel by using a nut, and the jack is connected with an oil pump;

and finally, carrying out hanging basket walking, wherein the main truss needs to be kept to synchronously move forwards during hanging basket walking, when the left hand thread wheel walks to a rail pressing beam, firstly pressing a rail pressing beam behind the left hand thread wheel, then dismantling the front pressing beam of the left hand thread wheel, after the main truss moves forwards, waiting until a lower cross beam box indoor reserved hole, aligning a rear anchor reserved hole with a cross beam lifting appliance, a rear anchor node box and the like, then immediately anchoring a rear anchor point of the hanging basket, then installing a rear bottom basket lifting rod and a wing plate lifting rod, loosening the walking rear lifting rod, adjusting the position and the elevation of the template, then moving the rolling lifting appliance to the reserved hole, threading the lifting rod again, and waiting for next walking.

5. The bridge stay cable lag tensioning construction process according to claim 1, characterized in that: d) during concrete pouring and curing, the concrete is intensively mixed, the two cantilever ends are symmetrically poured, the webs on the two sides of the same cantilever are also symmetrically poured, the unbalanced weight of the concrete put into the warehouse cannot exceed 1/4 of the weight of the beam section, a bottom plate, a web plate and a top plate are firstly poured during concrete pouring, and the sequence of symmetrically pouring the concrete by the two webs, namely front, rear and tail parts, is followed.

6. The bridge stay cable lag tensioning construction process according to claim 1, characterized in that: the e) tensioning three-way prestressed strand is a longitudinal, transverse and vertical steel strand, the prestressed steel strands are all steel strands, the steel strands are low-relaxation high-strength prestressed steel strands, the stress is controlled by adopting tensioning stress and elongation for double control, and the tensioning is balanced and uniform;

the tensioning sequence is longitudinal prestressed beam → transverse prestressed beam, diaphragm prestressed beam → vertical prestressed beam containing cable area, the vertical prestressed beam lags behind one beam section for tensioning, and the box girder top plate cantilever secondary tensioning prestress and the vertical prestress adopt low retraction secondary tensioning prestress anchoring system.

7. The bridge stay cable lag tensioning construction process according to claim 1, characterized in that: d) pouring and curing the concrete by covering and watering; and f), grouting, wherein a secondary grouting process is adopted in anchor sealing, after grouting and plastering are finished, geotextile is immediately adopted for covering, water is sprayed above the geotextile for moisturizing, both the web plate and the bottom plate are subjected to watering maintenance with a die, after prestress tensioning and grouting are finished, when the hanging basket moves forwards, the die plate is removed, and the maintenance time is not less than 7 days.

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