1, preface
The construction technology of pier from one formwork to top is a new technology in railway bridge construction. It has the advantages of fast construction speed, no construction joints, high engineering quality, safe construction, low labor intensity, low material consumption and less overall investment. Practice has proved that it has great advantages over conventional construction. This method is based on the design and construction practice of pier one-mold-to-top construction in the construction of Weihe No.5 Bridge on Baolan Second Line.
2. The characteristics of the construction method
2. 1 The concrete of pier shaft and pallet top cap has good integrity, no construction joints and easy quality assurance.
2.2 Simple structure, convenient disassembly, high degree of construction mechanization and fast construction speed. The aerial work of assembling formwork is changed to plane work, which has high construction safety.
2.3 Using the embedded parts at the top of the base to control the template position is simple and convenient.
2.4 template in place accurately, easy to operate, small deviation.
3. Scope of application
This construction method is suitable for the construction of circular, round and rectangular piers of railways and highways, and the pier height is within 20 meters.
4. Construction technology; That is, the process principle.
4. 1 process principle:
The key to the construction technology of one-mold-to-top one-step molding of pier is the design scheme of formwork and the measures to dismantle the whole formwork after concrete pouring. In order to facilitate hoisting, the formwork is still made in sections, with the height of each section controlled at about 4.0M The circular pier is designed into two semicircles, and the longitudinal and transverse joints of the formwork are reinforced with channel steel or flat steel. The template of the tray top cover should be divided into four or six parts according to the design requirements, and the joints of the template should be bonded with steel plates and polished flat. The whole template has no support except the tray. Formwork can be dismantled by "sequential dismantling method" or "reverse dismantling method". No matter which method is adopted, the height of pier formwork must be shortened by 3-5CM when designing formwork. When the formwork is erected, the wooden blocks are symmetrically padded, and the gaps between the wooden blocks are filled with clay (this part belongs to the junction of the foundation and the pier, which will not affect the appearance). When the formwork is dismantled, the cushion block should be dismantled first, and then the connecting bolts of the formwork should be moved to reduce the dead weight of the formwork, and the rest can be dismantled as usual.
4.2 Process flow chart:
4.3 Construction technology:
4.3. 1 construction preparation
In order to fully ensure the continuity of construction and reflect the characteristics of fast construction speed, adequate preparations should be made before construction.
1. ILO
Before construction, technical training and safety education should be given to the labor force in the construction process, and the combination of the two should be optimized to ensure the construction progress. (e.g. table 1)
Table 1 Labor Organization of Terminal Operation Team
2. Machines and materials
(1) Adjust the template according to the drawing and install it in place.
(2) The formwork connecting components are assembled in place, and all the steel materials of the scaffold are assembled in place.
(3) steel binding and production, embedded components for inspection and assembly in place.
(4) Transportation equipment, mixers, lifting equipment and vibrating equipment are well prepared.
(4) Pay-off the pier, draw the position of its cross-section member and the height of the cushion block, and make technical disclosure.
Template hoisting
(1) Before the pier formwork is assembled, it shall be polished smooth and the inner surface of the formwork shall be free from corrosion.
(2) The formwork shall be connected in layers on the ground, and the joints shall be glued and polished with steel plates.
(3) When the formwork is connected at high altitude, the joint of the formwork should be well overlapped, and the inner surface should be trimmed and polished as a whole after connection.
(4) Tray, top cover and bracket shall be assembled on the ground and hoisted as a whole.
(5) Scaffolding shall be erected at the support to support and reinforce the support to prevent stress concentration and deformation at the support.
(6) Build a discharging platform, and determine the length of the discharging hopper according to the height of the pier.
Pouring concrete
(1) In strict accordance with the construction order, control the concrete mix ratio, slump (appropriate control in 1cm) and various additives.
(2) When tamping, it should be tamped evenly by layers, and the tamping should be dense. Don't miss, pound or pound too deep, and don't get close to the formwork when tamping.
(3) When the concrete is poured into the pier, it should be aligned with the string tube to prevent the staff from being injured outside.
(4) In the process of pouring concrete, the formwork should be checked frequently to prevent the formwork from being deformed due to unstable reinforcement or slurry leakage.
(5) Check the quantity and location of embedded parts and steel bars.
(6) Make test blocks and pay attention to data collection.
4.3.4 Dismantle the formwork
(1) When the formwork is dismantled, the formwork shall be loosened as a whole, the formwork cushion block of pier shaft shall be removed, and then the formwork top cap tray shall be removed.
(2) When the formwork is dismantled, there should be a special person to direct it to prevent the formwork from colliding with the pier and affecting the quality of the pier.
(3) The bracket formwork shall be removed subsequently to ensure that the concrete at the bracket has sufficient strength and does not affect the quality of the pier.
5. Machines and equipment (as shown in Table 3)
6. Quality management
6. 1 quality standard (as shown in table 4)
6.2 Quality control
1. Formwork lap seam is smooth.
2. The formwork support size error is 3.0MM, the formwork center error is 10MM, and the section size is accurate.
3. The formwork shall be brushed with release agent step by step, and the concrete that gradually reaches the formwork during vibrating shall be removed before pouring.
4. Strictly control the mixture ratio of concrete and the slump of concrete.
5. In order to prevent template deformation or slurry leakage, lap welding should be carried out at the joint of the template to strengthen the template.
6. When pouring concrete, there should be full-time technical personnel to conduct on-site command operation to ensure the quality of pier.
7. Carefully check the positions of reserved holes and embedded parts, and handle the problems in time when found.
8. Set up a QC team to solve the key and difficult problems in the construction, ensure the quality and progress of the project, and pay attention to collecting data.
6.3 means of quality inspection
1. Check the center position of pier with photoelectric rangefinder.
2. The surface flatness of the formwork shall be detected by 2.0M guiding rule.
3. Use a 5.0M tape measure and a two-way ruler to detect the position of embedded parts and steel bars.
4. The height of the cushion block is detected by leveling.
5. Concrete pouring should be visually inspected, and the internal vibrator does not bubble when vibrating, and the moving distance is 40-50CM at a time.
7, construction safety precautions
1. Conduct pre-job training for aerial workers to strengthen safety awareness.
2. Aerial work personnel should wear safety belts and helmets, and it is forbidden to throw objects at high altitude.
3. Check the line frequently to prevent the electric wire from leaking.
4. Always check the lifting equipment and feed hopper, check the warranty of wire rope and reinforce the warranty of various fasteners.
5. Hang danger signs, warning signs in accordance with the provisions. Send a special security officer to check at any time to eliminate potential safety hazards.
6. The specialist is responsible for the command of lifting equipment and strengthen communication.
7. Strengthen post responsibilities, with clear rewards and punishments.
8. Benefit analysis
The benefits of this method are mainly manifested in the following aspects:
1. Reasonable and compact working procedure shortens the construction period by 30%.
2. Save 20% of the labor force10.5 million yuan, creating good benefits for enterprises and society.
3. The template procurement cost is lower, which is 50% lower than that of sliding mode and climbing mode, and the turnover times are more.
9, engineering examples
In the construction of No.5 extra-large bridge on Weihe River in Baolan Second Line, one-die jacking method was adopted, and good results were obtained. There are 2 1 piers with an average height of about 10M. It takes only 60 days to complete the cyclic construction with two sets of formwork. All piers were of good quality and no safety accidents occurred. The whole bridge was rated as "high-quality project" by the construction unit, which saved a lot of steel and labor, and created for the enterprise.
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