Second, the approach bridge capping beam construction
During pier construction, a through passage shall be reserved along the longitudinal direction at a distance of about 1 m from the pier top. During capping beam construction, a steel bar passes through the tunnel, and two I-beams are supported on the steel bar as the support of capping beam formwork. The bottom formwork and side formwork of capping beam adopt large steel formwork, and the steel skeleton is processed in the steel processing plant, transported to the pier top for welding and binding.
After the formwork is installed in place, check and reinforce it, and report it to the supervision engineer for inspection before pouring concrete. Concrete is mixed in a mixing station, transported by a concrete mixer, pumped into the mold, vibrated by an internal vibrator, once cast and molded, wrapped with plastic film, and maintained by sprinkling water.
Three, double thin-walled high pier construction method
The main piers 9# and 10# of Hanjiadian No.1 Bridge are double thin-walled piers with a thickness of 2.5m, a width of 12.6m and a clear distance of 7m. 9# pier is 73.66 1m high, 10# pier is 63.99 1m high, and there are two10m× 7m×1. 8# transition pier is a single thin-walled pier, with a thickness of 3.0m, a width of 12.2m and a height of 41.798m. The main pier body is constructed by large turnover formwork. The scheme has the characteristics of simple construction technology and fast construction speed.
1, construction of turnover system
The turnover mould system consists of a large section steel mould, a working platform and a lifting system. (See page 36 for the attached drawings).
(1) The pier formwork is a large composite steel formwork, and its size, stiffness and strength meet the design and specification requirements. Each set of pier formwork consists of three sections, each section is 2.5 meters high and the three sections are ***7.5 meters. The formwork is reinforced by adding horizontal back bars on the outside of each side formwork, and each back bar consists of two [12 channel steel. When the formwork is reinforced, it is anchored on the back ribbed channel steel by φ 16 round steel die-drawing reinforcement.
⑵ The template working platform consists of an internal working platform and an external working platform. The inner working platform is between two thin walls, and a bracket is set up with a bowl scaffold, and the bracket is paved with boards as the inner working platform. The whole scaffold is 0.4m away from the formwork as the formwork lifting space. The outer working platform is composed of wooden boards, in which triangular braces and handrails are welded with angle steel at the top of each outer die and round end die.
⑶ Lifting system: The lifting system consists of tower crane, construction elevator, concrete delivery pump and pump frame. Tower crane is the main lifting equipment for pier and beam construction, and also the formwork lifting equipment for formwork turnover; Construction elevator is used as lifting equipment for construction workers and small machinery; Concrete pump is the lifting equipment of concrete, and the pump frame is the auxiliary equipment of concrete pump pipe, cable and water pipe. In addition, a simple pedestrian ladder welded by steel bars is set in the pump frame as a passage for pipeline and cable maintenance personnel and an emergency passage in case of power failure.
2. Steel structure
The reinforcement construction of the main pier body is the same as that of the approach pier body, only the vertical main reinforcement is limited by the working platform, and the main reinforcement of the approach bridge is 4.5m
3, concrete construction
The concrete construction of the main pier pier is the same as that of the common pier of the approach bridge, except that the concrete grade is relatively high and the requirements for raw materials are higher. In addition, concrete is no longer poured into the mold with string tubes, but directly poured into the mold with pump tubes.
4, turnover formwork construction process
In the process of pier construction, the assembly of scaffold working platform, the binding of steel bars, the lifting of formwork and the pouring of concrete are carried out in cycles, and the three-section formwork of pier is also lifted from bottom to top. The whole construction process is uninterrupted and cyclic, so the construction speed is faster. See the next page for the process flow chart of turnover formwork construction:
(See the attachment for the picture)
5. Linear control of pier shaft in turnover formwork construction
The linear control of thin-walled pier is mainly carried out through construction survey. Construction survey control contents of thin-walled pier include: center positioning survey of thin-walled pier, elevation survey of thin-walled pier and verticality survey of thin-walled pier.
(1) control method
(1) Center Positioning Measurement of Thin-walled Pier
Adopt three-dimensional coordinate control method. Before the construction of each pier, the survey class of the project department will use the total station to locate the center. When positioning, more than one person should check it. After being checked and confirmed by the supervisor, horizontal and vertical piles should be set up, and disclosure should be made to the construction team. When rechecking the elevation, a precise level should be used for measurement.
② Height measurement of thin-walled pier
There are three methods for elevation measurement. One is to directly carry out elevation measurement with total station; The second is to measure the pier top with a steel ruler from the leveling point at the bottom of the pier; The third is to observe the top elevation of No.9 pier near No.7 pier with a level, and observe the top elevation of 1 10 pier on the subgrade behind No.0 abutment. In the end, the level measurement shall prevail, and the other two methods shall be used as rechecking means.
③ verticality measurement of thin-walled pier
The verticality of pier shaft is measured by automatic leveling laser plumb calibrator, and each thin wall is measured at four angles. During the measurement, the laser plumb calibrator is placed on the control point of the pier cap, and the control point is obtained through precise positioning measurement. The laser receiving target is installed on the pier top working platform, which can display the light spot and capture the center of the light spot. The plane position and verticality of each template of a single thin wall are controlled by four laser spot centers, and the verticality of the pier is controlled accordingly.
(2) Control measures
(1) Set up a capable survey team to be responsible for the survey of pier shafts, equipped with advanced measuring instruments to ensure the linear control of pier shafts;
(2) In order to prevent the deviation of pier shaft caused by instrument error, check the center point with traverse calibrator with total station every 10m, and retest the pier shaft size to ensure the linear control of pier shaft;
(3) Implement the system of changing hands to check the measurement data, and report it to the supervision engineer for examination and approval before it can be used for construction;
(4) In order to ensure the appearance quality of pier concrete, formwork processing shall conform to the basic provisions of Code for Construction and Acceptance of Steel Structure Engineering, and its surface shall be free of holes (except lacing holes), burrs, cracks and slag; Template assembly welding must be polished smooth; The upper and lower openings of the template should be trimmed; Formwork joints shall be laid with double-sided adhesive tape; Template assembly should meet the requirements of assembly accuracy.
The fourth quarter continuous rigid frame cantilever pouring construction method and technology
I. Overview
The upper part of the main bridge of Hanjiadian No.1 Bridge is a three-span prestressed concrete continuous rigid frame box girder bridge with a span of122+210+122m. Box girder is 0# long 15m, and each T-beam is longitudinally divided into 36 symmetrical beam segments. The number and length of beam segments are 10×2.2m, 10×2.5m, 13×3.0m and 3×3.5m respectively, and the total cantilever length is 98m. The whole bridge has three closure sections, namely, two side span closure sections and one middle span closure section. The length of closure section is 2m, and the cast-in-place section of side span is 16m.
The box girder is a three-dimensional prestressed structure with single box and single room section. The width of the box girder top plate is 22.5m, the width of the bottom plate is 1 1 m, the cantilever length of the outer wing plate is 5.75m, the height of the box girder root beam is1.2m, and the height of the mid-span beam is 3.5m .. The thickness of the box girder web in the pier top is 170cm, and the box girder root is/kloc. The bottom plate gradually transits from the box girder root 120cm to the span.
Second, the continuous rigid frame cantilever pouring construction scheme
1 construction organization arrangement of continuous rigid frame
Continuous rigid frame construction is the key and difficult point of the bridge construction. Therefore, in addition to the normal organization and leadership of the project department, the project department also set up a scientific and technological research team for Hanjiadian No.1 Bridge to focus on the construction of the beam. Regarding the arrangement of the construction team, the 11th Engineering Team of our company with rich experience in bridge construction will undertake the construction of the bridge. The eleventh engineering team has five classes, with 30 people in the first class, and is responsible for the construction of the remaining piers of the approach bridge, the 8# transition pier of the main bridge, 1 1# abutment and the cast-in-place sections on both sides of the main bridge. Class II and Class III are responsible for the construction of pier shafts of main piers 9# and 10# and their T-shaped structures. Class 2 and Class 3 are all made up of 80 coolies, such as reinforced class, concrete class, hanging basket class, formwork class and prestressed tensioning class. The fourth and fifth classes are all concrete production classes, each class has 15 people, who are responsible for the concrete production of Pier 7 and Pier 10 respectively. Another 50 people from the bridge company are responsible for the prefabrication and erection of the T-beam of the approach bridge.
2, continuous rigid frame construction period arrangement
The commencement date of the bridge is July 2002 1 day, and the expected completion date is April 30, 2005, with a total construction period of 34 months. For the specific construction progress plan, please refer to Annex 6: Hanjiadian 1 Construction Network Plan of Extra Large Bridge.
3. Main equipment for cantilever casting construction
Continuous rigid frame construction is the biggest difficulty of this bridge, which belongs to aerial work. Narrow and concentrated working face, tight construction period, complete and sufficient construction equipment play a vital role in construction speed, quality and safety. The main equipment supporting scheme of continuous rigid frame construction is: mixing concrete in mixing station, transporting concrete by car and pumping concrete to working face; The tower crane undertakes the vertical transportation of hanging basket installation, steel bars, templates and other materials; Industrial elevators take workers and small machines up and down; Hanging basket bears the main load of hanging irrigation, and is equipped with prestress equipment, grouting equipment and winch.
4, beam construction technology
(1) construction method
① Construction of Block 0: The corbel is embedded in the concrete at the pier top, then the universal bar is assembled to form the overhead support, the strength of the support is strictly checked, the elastic deformation is calculated, the inelastic deformation is eliminated by preloading the precast concrete block, and the elastic deformation is measured. Laying vertical and horizontal channel steel on the support as distribution beam, then installing square timber on it, finally laying formwork, binding steel bar and pouring 0 # block. The bottom formwork adopts hanging basket bottom formwork, the two ends of the side formwork adopt hanging basket formwork, the middle adopts pier formwork and flange-processing steel formwork, and the internal formwork consists of large steel formwork for bearing platform and some small assembled steel formwork, supplemented by some special-shaped steel formwork.
Block 0 is poured in three times, the first time to the lower edge of diaphragm hole (height 3.0m, concrete 380m3), the second time to the lower side of reserved channel of longitudinal prestressed steel strand (height 0.43m, concrete 580m3), and the third time to the top plate (height 3. 1m, concrete 320m3).
(2) 1 ~ 36 cantilever casting
Triangular hanging basket is used for hanging basket, and the weight is controlled within 120t. The construction procedures are: hanging basket installation → preloading and detection of hanging basket → adjustment of elevation and center line → positioning of external formwork → binding of bottom plate and web reinforcement and prestressed pipe → positioning of internal formwork → binding of top plate reinforcement and prestressed pipe → pouring concrete with equal strength → tensioning and grouting of prestress, and moving the hanging basket for the next cycle. According to the linear control data, the template placement of each beam section is adjusted, the concrete pouring is carried out symmetrically on both sides of the T-shaped structure, the concrete is lifted by the pump, other materials are lifted by the tower crane, the personnel are lifted up and down by the construction elevator, the prestressed tensioning is carried out in strict accordance with the specifications, and the linear control and stress monitoring of the cantilever beam body are implemented by the monitoring unit.
③ Construction of side span cast-in-place section
The cast-in-place section of the side span of Hanjiadian No.1 Bridge is 16m long, the pier No.8 is 42m high, and the outer side of abutment No.0 is1/6m high. The ground longitudinal slope is steep and the construction is difficult. In view of this situation, it is decided to adopt scaffolding method for construction. Scaffolding is set up with military equipment, with type 83 military pier as scaffold pier and type 64 military beam as scaffold beam. Large steel formwork is used for the outer die and bottom die, and combined steel formwork is used for the inner die.
(4) Construction of closed section
The closed parts of side spans A and B shall be built directly on scaffolding. C, across the closed section using hanging basket template system. Before construction, the two beams should be consolidated and the method of internal consolidation should be adopted. The pouring time should be in the middle-low temperature constant temperature period, and the temperature should be controlled at 10 ~ 15℃.
⑤ Prestressed construction
The beam part is designed as three-dimensional prestress, that is, longitudinal, vertical and transverse. Pre-stressed tendons shall be laid with a special blanking pedestal on the ground, which shall be laid, numbered and stored according to the construction sequence. The tower crane supplies materials, and the longitudinal and transverse prestressed channels are perforated with metal bellows. Tees or multi-pass pipes should be set for the long channel of longitudinal reinforcement to facilitate grouting, and special through holes and beam guiding tools should be worn for long beams. The tensioning sequence and tonnage are strictly controlled according to the design requirements. Prestressed tension has a great influence on the internal force of the beam, so the principle of symmetrical synchronous construction should be adhered to.
(2) Process flow
The beam construction technology includes 0# block construction, standard segment construction, closure segment construction, side span cast-in-place segment construction, prestress construction, etc. The process flow chart is as follows:
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