Cable-stayed bridge, also known as inclined Zhang Qiao, is a kind of bridge with many cables and the main girder directly pulled on the tower. It is a structural system composed of pressure-bearing tower, tension cables and curved beams. The following is the construction technology case of the main tower of cable-stayed bridge that I compiled for you. Welcome to read and browse.
I. Overview of the Project
The Shangdi Railway Separation Interchange of Beijing-Xinjiang Expressway (5th-6th Ring Road Section) is a part of Beijing-Baotou Expressway Project, with a total length of 5 10 m, and is a 46+46+230+98+90 m five-span continuous single-tower single-cable plane prestressed reinforced concrete cable-stayed bridge. This bridge crosses the existing beijing-baotou railway and subway 13 line, and the intersection with the existing beijing-baotou railway with railway mileage K22+756, highway mileage K3+55.703 and intersection angle 19 degrees.
The main tower of stay cable is located in downtown area, with narrow site, subway station and dense residential area in front, gas station and dense residential area behind, underground passages on both sides, and 13 subway line and Beijing-Baotou line in the middle. The complex construction environment is the key and difficult point of the whole project construction.
Second, the tower column construction overall plan
1. Overview of the overall scheme
The height of the main tower column of this bridge is 99 m from the top of the pile cap, which is in the shape of a drop of water, and consists of three parts: lower tower column, middle tower column and upper tower column. Height of lower tower column11m. The middle tower column is 40 m high, which is a rectangular variable cross-section double inclined column with an internal inclination of 22? 43'08''。 The upper tower column is 48 m high, rectangular variable cross section with notch, straight line+circular curve.
The lower tower column is poured integrally at one time by conventional technology, and the middle and upper tower columns are constructed in 20 sections. After the first two sections are completed, hydraulic climbing formwork construction will be adopted from the third section. Climbing formwork is 4.25 m in each section, and the construction period of each section is 5 ~ 7 d.
Aiming at the unique shape structure of tower column, combined with the previous experience of climbing formwork construction, the existing technology is improved from three aspects: the selection, assembly and construction of formwork system, which solves the problem of mutual conversion and adjustment between straight and curved structures in the construction process.
2. Template selection
All templates are steel templates. The steel die has great strength and rigidity, which can meet the requirements of multiple disassembly, reorganization and recycling of climbing die equipment. Secondly, the steel formwork technology is mature, the operation process is relatively simple and the assembly is convenient. At the same time, it can ensure that the concrete surface of the tower column is smooth and the appearance quality is good.
3. Processing and assembly of climbing formwork system
All components of climbing formwork system are prefabricated by professional manufacturers. According to the actual construction situation, determine the structural size and the most economical climbing formwork segment, and transport them to the site for structural assembly after inspection and acceptance.
The climbing frame system includes: suspension and embedded parts, climbing guide rail, hydraulic jacking equipment, two upper working platforms, 1 main working platform, two lower working platforms, etc.
The width of the main operating platform is 3.3 m, and the total height of the platform is15 m. The main operating platform is composed of triangular supports and section steel, which bears the weight and construction load of the whole climbing frame and transmits the load to the poured concrete entity through embedded parts.
There are two working platforms on the upper part of the main working platform, which are used for formwork support, mold closing and concrete pouring respectively.
Two working platforms are suspended below the main working platform for hydraulic climbing operation and concrete solid decoration.
All platform components are connected by section steel, and the components can be disassembled and transported. They are connected by bolts and pins, which is very convenient and quick to disassemble and assemble.
Three. Working principle and process of climbing formwork construction
1, climbing formwork construction working principle
The lifting movement of the climbing formwork is realized by the hydraulic cylinder alternately lifting the guide rail and the climbing frame. The guide rail and the climbing form are not related to each other and can move relatively. When the climbing formwork works, both the guide rail and the climbing formwork are supported on the embedded bracket, and there is no relative movement between them.
Immediately after demoulding, install bearing bolt and hook connection seat on the climbing cone left after demoulding, adjust the direction of upper and lower yoke claws, and jack up the guide rail. When the guide rail is jacked into place and located on the hook connection seat, the operator immediately goes to the lower platform to remove the hook connection seat and the climbing cone exposed on the lower platform after lifting the guide rail.
After all the knots on the climbing formwork are untied, the climbing formwork can be hoisted. At this point, the guide rail remains stationary. After adjusting the direction of the upper and lower pawls, start the oil cylinder and move the climbing die relative to the guide rail. By alternately attaching the guide rail and the climbing formwork, the climbing formwork can be lifted along the reserved climbing cone on the tower.
When climbing the track, the upper climbing box does not move, and the oil cylinder extends, so that the bearing seat in the lower climbing box is supported under the step block of the track. Retract the cylinder and raise the track.
After being in place, the bearing seat in the climbing box supports the track to complete a working cycle. This cycle until the track is in place.
When climbing the scaffold, the bearing block in the climbing box is pressed on the step block of the track, and the oil cylinder extends out to jack up the formwork. After being in place, the bearing block in the climbing box is pressed on the step block of the track, and the formwork rises to a height. The oil cylinder contracts, and the lower climbing box is lifted to the top of the previous step block to complete a working cycle. This cycle until the frame is in place.
2, climbing formwork construction process
Trial assembly of climbing formwork system? Steel binding, embedded parts installation? Site installation of climbing formwork system? Climbing formwork system? Is the formwork used for reinforcement in place? Climbing formwork system for concrete demolition
Four, climbing formwork construction key control points
1, adjustable template system
The upper part of the middle tower column starts from 7 sections, and the structure changes from straight section to circular section. Because the thickness error of protective layer of tower column can't exceed 5 mm, it can't be replaced by straight section, which requires that the template can be adjusted.
Due to the change of structural modeling, in the process of formwork system climbing, it is necessary to transform the structural characteristics of formwork according to the structural characteristics to meet the construction requirements. In the construction process, the hydraulic steel climbing formwork completes the construction of straight and curved sections of the whole structure through the structural transformation of small components.
In the structural transformation of straight-curve conversion construction, the original straight-line climbing is changed into curve climbing, and the opposite curve climbing is changed into straight-line climbing. By adjusting the template design modification device, the template is adjusted from a straight line to a curved line, the positioning block of the track climbing kit is adjusted to meet the straight line requirements of the curved track, the distance between the track climbing step blocks is changed, and the height of each lifting is adjusted.
With the construction progress of the project, after each stage of structural construction is completed, the spatial position of the whole frame structure members should be adjusted to meet the spatial position and safety requirements of the construction platform.
After pouring the previous section of concrete, if it is necessary to adjust the curvature of the cambered surface, it is not necessary to dismantle the formwork, just use the adjusting bolt.
Because the steel plate has a certain toughness, it will be deformed without being destroyed after an appropriate external force is applied. Using this feature, through the principle of geometry, when using, if the curvature needs to be changed, just loosen the bolts, which can be accurate to every thread and bend the panel into the radian required by the design.
Moreover, the steel formwork has high turnover rate, convenient installation and disassembly, and good concrete molding appearance, which can greatly speed up the construction progress and meet the quality requirements of concrete pouring.
In the process of construction, the change of radian leads to different adjustment angles every time. This requires that the interface should be disconnected in the process of adjusting the template. The gap at the interface can be sealed with glass glue or filled with putty.
Because of the transition from straight section to circular section, and the linear guide rail can only move along the straight line, in order to meet the needs of climbing and saving materials, the track removed from the inner side can be pressed to be parallel to the solid arc on site, so that the guide rail can travel along the solid arc.
Because the angle of each climb is different, it is necessary to use tower crane to adjust the angle during the climb to ensure that the guide rail can be positioned on the wall-attached device smoothly.
2. Installation of steel bars and embedded parts
The steel bar of tower column is mainly connected by straight thread joints, and the steel bar connection is carried out after the rigid skeleton is installed in place, relying on the rigid skeleton for positioning.
The connection method is as follows: measure the vertical and horizontal axes of the discharge tower column on the extended rigid frame with total station; Steel bar construction personnel set out the installation position line of steel bars on the rigid frame according to the longitudinal and transverse axes of the tower column; The tower crane lifts the main reinforcement and connects it with the main reinforcement in the next section; Connect two steel bars by rotating the sleeve with a pipe wrench; Then locate and fix the main reinforcement according to the position of the main reinforcement released from the rigid frame.
When setting embedded parts, we should not only pay attention to the correct position and quantity, but also pay attention to the surrounding steel bars and templates to prevent the dislocation of concrete pouring. The allowable deviation of the positioning center of the climbing cone should be? Five millimeters.
For the exposed permanent embedded parts, do a good job of anticorrosion and pollution prevention, and remove the temporary embedded parts in time after the project is completed and the concrete surface is repaired.
3, climbing formwork site installation
First, assemble the platform of the main load-bearing structure and the operating platform of the auxiliary structure. After the platform is assembled, the platform of the main load-bearing structure is hoisted to the positioning embedded parts of the embedded climbing formwork construction, and the support legs of the frame and the positioning pin bolts are adjusted for fixing. After the main platform is installed, the attached light operating platform should be installed from top to bottom, and the installation position should correspond to the internal and external positions of the main platform.
After the tower column is poured to the foundation height required for the installation of climbing frame, the installation of climbing frame and formwork is started. The installation sequence of climbing frame is platform 0, platform-1, platform+1, platform +2 and platform -2. Each unit is assembled on the assembly platform respectively, and then hoisted and installed on the embedded parts of the tower column as a whole.
After the installation of the main attachment platform is completed, hoist the guide rail and template with tower crane. The guide rail and the template are installed downwards from the upper part of the frame body. In the process of inserting the guide rail, attention should be paid to the position of the track axis to meet the construction requirements. After all the components are installed, the positioning adjustment of the frame components shall be carried out to meet the requirements of construction operation.
The installation of formwork shall be carried out after the installation and adjustment of climbing frame is completed. When the formwork is assembled, it must be aligned block by block in sequence, temporarily fixed after being connected into a frame, and fine-tuned by hydraulic jack. It is forbidden to pull the hard top to deform the template.
Frame protection facilities shall be installed after the structure is assembled.
4. Climbing of climbing formwork system
(1) A special command and management organization and management system must be established for climbing construction. Console operators should receive professional training, and operate with certificates after passing the training. It is strictly forbidden for other personnel to operate.
(2) Before the guide rail climbs, its climbing contact surface shall be cleared of adhesive and coated with lubricant. Check whether the load-bearing block of the climbing box is in the state of lifting the guide rail, confirm that the frame body is fixed on the load-bearing body and structure, and confirm that the guide rail locking wedge and the bottom support are loose.
(3) The climbing of the guide rail is automatically completed by the oil cylinder and the upper and lower climbing boxes. In the process of climbing, there should be a special person to ensure that the guide rail is accurately inserted into the upper hook connection seat.
(4) After the guide rail enters the hook connection seat, it is necessary to insert the wedge to block the upper end of the guide rail in time, adjust the support at the bottom of the guide rail at the same time, and then switch the climbing function of the load-bearing block of the climbing box so that the frame body is supported on the guide rail step block.
(5) Before the frame body and formwork climb, all tie rods and obstacles hindering climbing on the formwork should be removed; Remove the surplus materials on the frame body, release the connection between the adjacent segmented frame bodies and between the frame body and the tower body, and confirm that the climbing box is in the climbing working state; Disconnect the four corners of the insulation shed and the pedal of the working platform. Check that the hydraulic equipment is in normal working condition, the concrete strength at the bearing body meets the climbing requirements of the frame body, and confirm that the legs of the frame body have been retracted and the safety bolts have been pulled out; Before the frame climbs, safety inspection must be organized, and it can only climb if it is qualified.
(6) Climbing should be under the unified command of the commander-in-chief, and each section should be equipped with enough monitoring personnel.
(7) When the frame climbs to the hook connection seat, the safety bolt shall be inserted in time. And screw out the adjusting leg of the frame body and push it against the tower body, so that the frame body can be transformed from climbing state to construction fixed state.
(8) If there is any deviation in the formwork climbing process, it shall be corrected immediately. For the overall deviation of the formwork climbing device, steel wire rope and manual hoist can be used to correct the deviation; For local deviation, the section and verticality of the formwork can be adjusted by the leg adjusting screw.
5, concrete pouring
After the formwork reinforcement is completed, concrete pouring construction will be carried out, and the concrete will be pumped and poured by car. Strengthen vibrating construction and maintenance construction after formwork removal to ensure the quality of concrete construction.
After concrete pouring, the internal and external joints of the top surface of concrete with a width of about 1.5 cm near the formwork shall be trimmed, compacted and smoothed based on the top line of the formwork. When the construction joint is chiseled, it is forbidden to destroy this joint to ensure that the upper and lower concrete joints are straight.
Chiseling is done by hand. When the concrete strength of the treatment layer reaches 2.5 mPa, the cement mortar and soft layer on the concrete surface are chiseled manually, and the chiseled concrete surface is cleaned with compressed air or high-pressure fresh water.
Because there is no interface formwork at the bottom of the bridge tower formwork, in order to prevent slurry leakage and excessive dislocation of the joint between the upper and lower sections of concrete during concrete pouring, the bottom of the formwork for the section to be poured should be close to the outer surface of the top of the poured section of concrete, and no gap can be left.
Before concrete pouring, check and clean the joint surface again; In the process of concrete pouring, the adhesion between the formwork and the concrete surface of the lower segment should be observed at any time. If there is slurry leakage, immediately tighten the pull rod nut and support screw at the corresponding position; Concrete on both sides of the joint should be fully vibrated to make the joint full and dense.
6. Dismantle the climbing formwork system
Demolition work follows the order from top to bottom. First, dismantle the overlay, then dismantle the formwork and upper frame, and finally dismantle the lower platform and load-bearing structure.
Verb (abbreviation of verb) abstract
The curved climbing formwork construction of hydraulic steel formwork can meet the construction requirements of tower columns with different inclination angles and different linear sizes. A set of construction equipment can complete the whole structural engineering construction, which can save manpower, material resources and equipment to the greatest extent, reduce the turnover of construction equipment, improve construction efficiency, and ensure construction safety and structural appearance quality.
In the construction of Shanghai-Shanghai railway separation interchange project, the whole formwork climbing system does not need external power, and only the electric hydraulic system is used to lift the formwork. The whole formwork system realizes zero emission, does not produce any pollution to the construction environment, creates a good living environment for the private enterprises in Beijing where the project is located, and meets the requirements of the project on time limit, quality, safety and economy.
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