I. Basis for compilation
1, Design of South Canal Bridge
2. Technical Specification for Construction of Highway Bridges and Culverts
Second, the project overview
1, natural geographical environment
South Canal Bridge is located in Qingxian-Wuqiao section of Beijing-Shanghai Expressway, with the central pile number K64+036, which spans the South Canal. The South Canal is a three-level navigable river, with flat terrain on both sides of the bridge and hilly areas.
2. Design overview
The South Canal Bridge is 335 meters long. The main bridge is a three-hole prestressed continuous rigid frame (V-shaped pier) with a span of 60m, 35m on each side and a length of130m. The approach bridge at the north end is a 2-hole prestressed simply supported and then continuous hollow slab, and the approach bridge at the south end is a 6-hole prestressed simply supported and then continuous hollow slab. The whole bridge is located on the horizontal curve with the radius r = 5,500m of the road centerline. The bridge is horizontally divided into two bridges, each with a width of 13.5m, a drop of 1m and a total width of 28m. The main bridge adopts No.50 concrete, and the concrete quantity of each frame is 1205m 3.
3. Hydrological and geological conditions
The design flow of the bridge site is 120m3/s, and the corresponding design water level 13.5m (Yellow Sea elevation) is also the highest navigable water level, with a navigable clearance of 7m and a navigable clearance of 50m.
According to the geological histogram at the bridge site, about 4m below the surface is yellow medium liquid clay or yellow clayey silt, which loosely contains plant roots and wormholes. Bearing capacity 180kpa, the second layer is below it, with a thickness of about 3m, yellow-brown sandy soil, and the bearing capacity of dense hard plastic is 200 kPa. The third layer is white silt, with a thickness of about 5m, uniform particles, horizontal layers and sufficient water content.
Bearing capacity is 150 kpa. Further down are three layers of soil, which are basically muddy clay and grayish yellow silty sand, containing timely and feldspar, with a relatively dense structure and bearing capacity of 180-200 kPa.
Third, the overall construction plan
The superstructure of the main bridge of NanYunhe Bridge is a cast-in-place prestressed continuous box girder structure. Because there is water in the main river, in order to avoid setting more temporary piers in the water, the pier beam structure is adopted for the main span of the 60-meter main bridge. The temporary pier built in the water is the foundation of the pier, the military pier of the 65-year railway is the pier, and the military beam of the 64-year railway is the beam. However, on the bridge with a span of 35 meters on both sides, the terrain is relatively flat and there is no water accumulation, so the full-house steel pipe bent is used as the support, and the support is located on the treated foundation. The above construction scheme is adopted to construct the superstructure of the main bridge of the bridge.
Because the bridge is on a horizontal curve, the span and beam height are inconsistent. In order to increase the utilization rate of formwork and improve the appearance quality of beam concrete, the bottom formwork, outer formwork and inner formwork are all made of bamboo plywood with double-sided film covering, which is convenient for assembly. The inner and outer formwork frames are made of wood.
According to the design requirements, the main bridge is cast in two sections with integral cast-in-place support, and the length is 130m. First, the first section is 86m long, including 60m middle hole and 13m side hole. After the concrete reaches the design strength, the prestressed tendons are tensioned, and then the remaining 22m long beam sections on both sides are poured.
Four. Main construction methods and technological process of superstructure
The superstructure of the main bridge is a prestressed reinforced concrete box continuous beam with three spans cast-in-place on bearings.
1, construction preparation
1 Before the cast-in-place construction of the support, the preparatory work for the superstructure construction should be started.
Its main contents are as follows:
A, according to the process requirements for beam concrete mixture ratio test;
B, preparing materials according to the construction technical requirements and processing the template;
C, overhaul and purchase the main machines and tools used for beam construction;
D, rational allocation of labor, especially the personnel of various professional jobs; E, technical cadres familiar with drawings, steel cutting processing in advance.
F, the superstructure construction personnel shall receive pre-job training in the form of technical beams above.
2. Supporting structure
(1) Structure of the support
See the bracket design drawing for the bracket form of the middle span and side span of the main bridge.
The support mainly includes buttress foundation, buttress, cross beam, longitudinal beam and cross beam supporting formwork. The pier foundation adopts concrete expansion foundation, the pier adopts steel pipe bent and 65-type railway military pier, the cross beam adopts section steel, and the longitudinal beam adopts section steel and 64-type railway military beam. In order to enhance the integrity, steel beams are used as diagonal braces in the transverse connection between military beams of June 4th Railway. Square timber or section steel is placed on the longitudinal beam to support the formwork.
② Force analysis and calculation
The support is designed as a simple-supported and continuous structural system, and the stress analysis and calculation mainly consider the bearing capacity of foundation, internal force of pier and internal force of longitudinal beam (detailed calculation is omitted).
The vertical load includes beam section weight, formwork weight, vertical and horizontal beam weight, crowd and working load, and horizontal wind load.
③ Setting of pre-camber
The setting of pre-camber is closely related to the deformation of longitudinal beam, and both section steel and military beam are rigid members. Because the supporting foundation is an enlarged concrete foundation, and the buttress is also a rigid military pier and steel pipe bent, the deformation is very small. The deformation of the joint with the cushion beam can be based on the gauge.
Fan "value, so the military beam is the longitudinal beam of the support, and its camber is only the deflection of the pin hole and the elastic deformation of the support beam under the common load. The deflection of the pin hole has already occurred after the support beam is erected. Elastic deformation can be calculated accurately, steel pipe bent as the support of pier has good integrity, and the settlement of deformation can also be determined by combining theoretical calculation with empirical estimation. Therefore, in the construction process, the setting amount of pre-camber can be accurately set according to the calculated value.
3, template construction
① Template design
Because the box-shaped continuous beam of the bridge is located on the plane curve, and the transverse slope is set in rigid rotation, the beam height is constantly changing, which brings difficulties to the formwork design. In addition, the construction period of this bridge is tight, and a single template cannot be reused, so one-time use is considered in the design. Both internal and external formwork and bottom formwork are made of large double-sided coated bamboo plywood, formwork frame is made of wooden frame, and the cross slope of box girder is adjusted with wooden wedge. See template design for details.
(2) Template production and installation
ⅰ, template production
A, template production, outer frame and inner frame can be prefabricated on the ground in advance, and other parts can be made and installed on the bracket.
B, making bar size should comply with the drawing design requirements.
C, to ensure the quality of wood, damaged and rotten wood shall not be used.
Ⅱ. Formwork fabrication and installation process: placing stow wood, longitudinal wood → wooden wedge → transverse wood → detecting vertical and horizontal elevation and determining the center line of the line → releasing the size details of beam bottom plate → laying nail bottom formwork → binding beam bottom plate reinforcement → placing internal formwork → binding top plate reinforcement → pouring concrete. Ⅲ. Technical Requirements and Precautions for Template Fabrication and Installation
A, template production before installation, must again check whether the support center and elevation meet the design requirements. Only after passing the inspection can production and installation be carried out.
B, adjust the height of each wedge, should according to the provided construction camber height, with the midpoint of the beam span as the highest, according to the quadratic parabola adjustment.
C, the thickness of each point stow-wood should be determined according to the design size of box girder transverse slope, and should be further checked and rechecked after placement.
D, after the crossbar is placed, except the cloth is 50cm away from the center, the crossbar center is orthogonal to the center line of the line.
E, stow-wood, longitudinal wood, wedge, crossbar put in place, the interconnection position should be locked with nails to prevent loosening.
F, vertical and horizontal wood can be made of long, when need to extend, the joint must be in the position of stow-wood and wedge.
G, carefully determine the center line and put away the beam bottom size details to ensure the quality of template installation.
H, bamboo veneer panel joint template, nail shop after application of white lime paste filling screeding, seam residual lime slag should be removed.
I, before steel binding, bamboo veneer surface should be coated with release agent, before pouring concrete, the construction waste on the board surface should be removed and rinsed with water.
4, prestressed concrete box girder construction
The prestressed concrete box continuous beam of the main bridge has a length of130m, a span combination of 35+60+35m, a height of1.3m at both ends, a height of1.3m at the middle span, a height of 2.5m at the pier top beam and a width of13.5m at the top and bottom. ..
Process flow chart of cast-in-place construction of prestressed box girder
Military beam assembly, formwork processing → preparation → temporary pier foundation construction ↓
Measure the elevation → Assemble the support ← Install the beam dropping equipment ↓
Check the elevation → install the bottom die ← preset camber.
cheque
Binding positioning steel bar
Steel strand blanking, bundling and numbering
↓ Install the external formwork ↓ Check the size, position and elevation ↓→ Tie the bottom and web reinforcement ↓→ Install the corrugated pipe → Check the joint ↓→ Wear the steel strand ↓ Install the internal formwork ↓ Tie the roof reinforcement ↓ Pour the concrete in sections in sequence → Make the specimen ↓ Maintain ↓ Remove the formwork ↓
stretching
↓
Mud jacking pump
↓
Anchor seal
↓
Unloading bracket
? Preparatory work/about to start work
Because the middle span of the main bridge is in the water, the temporary pier foundation construction of the support can be completed in advance by using the trestle according to the support design drawing. Carry out pier fabrication, military beam assembly and template processing.
? Installing support
According to the construction design drawings, scaffolding is set up on the trestle and waterless land by crane.
? Installation template
Install the bottom formwork first, and then install the side formwork, all of which are hoisted by crane. The bottom die is directly fixed on the bracket with square wood, and the elevation of the bottom die is adjusted with wooden wedge. The side formwork shall be hoisted in sections according to the number, and the side formwork on both sides shall be wedged into wooden wedges, and the elevation shall be adjusted with wooden wedges. The amount of wooden wedge is large during construction, so attention should be paid to the accuracy and stability of position and elevation when installing formwork to ensure the overall size of the structure and the linear shape of the beam.
? Fabrication and installation of steel skeleton
In order to speed up the construction progress, ordinary steel bars can be specially made under the bridge, and the pedestal can be made into skeleton or steel mesh, and the length depends on the stress and hoisting capacity of the beam. In the process of skeleton making, we should pay attention to the influence of beam plane curve, as well as the bottom plate skeleton and web bone made.
The frame is put into the bottom mold and the outer mold in turn, and then welded in sections, and then the inner mold is installed in sections, and finally the roof steel bar is bound.
? Install prestressed pipes and steel strands.
The longitudinal design of the main bridge is full-length prestressed tendons, and the middle is connected by fasteners. High-strength and low-relaxation steel strand with a diameter of 15.24mm is adopted, with standard tensile strength Ryb = 1860 MPa, σ k = 1302 MPa, and each strand is 9-7 φ 5 mm and 12-7 φ. When drilling the corrugated pipe, when binding the web reinforcement, place the corrugated pipe according to the design position and fix the corrugated pipe with the positioning net. After checking the position accurately, spot weld the positioning net with the steel skeleton, and the spacing between the positioning nets is not more than 50cm.
Steel strand threading adopts two ways: manual threading and winch threading, which cooperate with each other to thread steel strand from one end to the other.
? Installing internal mold
After binding the bottom formwork and web reinforcement, install the internal formwork in turn according to the number. ? Bonding roof reinforcement
? Sedimentary concrete
The concrete label of the prestressed box continuous beam of the main bridge is designed as C50, which is uniformly mixed and pumped in the concrete mixing station.
Concrete pouring shall be carried out by sections and layers in sequence. The beam section is divided into the first pouring section with a length of 86m, including 60m middle hole and 13m side hole. After the concrete reaches the design strength, pour the remaining 22m beam sections on both sides. The pouring sequence is from two sides to the middle. According to the Technical Specification for Construction of Highway Bridges and Culverts and the Manual for Construction of Highway Bridges and Culverts, when pouring continuous beam concrete on the supports, the piers and supports will have uneven settlement. In order to prevent the pier from cracking, this bridge adopts the method of setting construction joints to solve it.
The pier top beam is high, and a series of pouring cylinders are set, and the concrete of other beam sections can be directly poured into the formwork. Before pouring concrete, technical disclosure shall be made to the vibrating personnel, and the position of the bellows shall be clearly stated to prevent the vibrating rod from directly contacting the bellows. In the process of pouring concrete, the steel strand should be twitched in time to prevent the pipeline from being blocked.
The construction points are as follows:
A, bottom die, outer die and inner die are segmented discontinuously.
B, floor, web reinforcement continuously open, roof reinforcement disconnected.
C, each paragraph requires a perfusion molding.
D, pouring concrete on the pier top and bottom plate, with skylight on the top plate, which is convenient for direct pouring concrete.
Enter the floor.
E, using internal vibrator vibration, vibrating floor to homework in the box, pay attention to
Vibration mass.
F, control the concrete into the mold speed, try to reduce the impact.
G, after all the concrete pouring, clean up the site, strengthen the health preservation work, and ensure the maintenance.
Hygienic quality is qualified, and the curing time is generally not less than 7 days.
? Health maintenance
? stretching
I. Preparations
Before tensioning, the jack and oil gauge should be calibrated, and the steel strand and anchorage should be calibrated.
Testing.
B, tensioning construction
When the concrete strength reaches 100%, the prestressed tendons should be tensioned. Symmetry at both ends
In the tensioning method, the tensioning sequence is from bottom to top, from both sides to the middle, and the tensioning of steel beams adopts the method of two controls, that is, the tensioning is controlled by prestress and the elongation is taken as a reference.
Check each other. The tensioning procedure is as follows:
0→ 10%σk (initial tensioning) → 100%σk (holding load for 5 minutes) → anchoring.
The tensioning process is as shown in the figure.
Beam concrete strength inspection, tensioning equipment inspection → preparation ←
Check and deal with the concrete under the anchor pad ↓ Communication equipment is ready to install tensioning equipment.
Labor organization for stretching irrigation channels ↓
Anchorage, passage and jack are centered.
↓
Initial tension/measured elongation ↓
Tension for controlling tonnage/measuring elongation value ↓
anchor
↓
Hole grouting
↓
Anchor seal
(1) grouting
After tensioning, grouting shall be carried out in time. Because the pipeline is long, two grouting machines are used to grout from both ends to the middle at the same time, and a slurry hole (exhaust) is set at the top beam of the pier until the slurry hole discharges the slurry with the specified consistency. Attention should be paid to when grouting:
A, water cement ratio should be controlled in 0.4-0.5, consistency should be controlled between 14- 18s, and the maximum moisture content should not exceed 4%.
B, the maximum grouting pressure can be controlled in 0.5-0.7 μ Pa, and the slurry should have a certain pressure stabilizing time after being discharged from the slurry outlet.
C, before grouting, the channel must be rinsed clean, and then the accumulated water will be blown out with an air compressor. D, grouting should be carried out slowly and evenly, without stopping halfway, and one injection is completed. If the downtime is long, the pressed cement slurry should be washed clean. E, grouting, each class should take specimens, fill in the construction records. (2) Anchor sealing
(3) Dismantle the formwork and support.
After the concrete of the beam reaches 80% of the design strength, the external formwork can be removed, the formwork can be removed with a wooden wedge, the bracket can be removed after tensioning grouting, and the material can also be discharged with a wooden wedge. Demolition sequence shall be carried out according to the sequence of crossing both sides first and then crossing the middle. The support shall be unloaded circularly from the middle of the span to the middle of the span, first small and then large, symmetrically and evenly in the longitudinal direction, and horizontally together. Designate a special person to observe the abnormal changes of the beam body with instruments and make records.
V. Construction guarantee measures 1 and technical guarantee measures
(1) Strengthen the functions of the technical management system headed by the project chief engineer. The project department has chief engineer, construction technology department, quality inspection department, financial planning department, material equipment department and other functional departments, and the technology
The management system is responsible for the joint review of design documents, design change management, technical disclosure, measurement assessment, commencement report, preparation of implementation construction organization design and construction calculation quota management. In the process of construction, the performance standards of materials and semi-finished products are examined and approved, and the construction technical files are managed, so that the whole construction process can run under the effective control of design documents, technical standards and construction specifications.
(2) Engineers with bridge construction experience are transferred from the bureau to form a working group, which is responsible for tackling key technical problems in construction, discussing construction technical schemes, proposing construction technical measures and solving technical problems in construction.
(3) Do a good job in technical disclosure, strengthen construction technical training, conduct written technical disclosure and major engineering operations for the construction team, organize technical training, and hold a certificate of approval.
(4) Do a good job in technical management of the construction site, equip the construction team with technicians, surveyors and quality inspectors, and be responsible for the technical management of the construction team. The project department should strengthen the guidance, inspection and supervision of on-site construction technical guarantee measures.
⑤ Strengthen the cooperation and cooperation with the construction unit, supervision unit, design unit and other relevant units, and report the design changes in the construction process in time to get the guidance of the owner, supervision unit and design unit. 2, quality assurance measures
(1) The project department and the construction team shall establish a technical management network with TQM first responsibility manager and chief engineer in charge, and employ experts as technical consultants.
(2) Implement a graded quality management system, which is responsible at different levels. The project department shall set up a quality inspection department, and a special person shall be responsible for the engineering quality of this contract. The construction team shall set up a full-time quality inspection engineer to be responsible for the quality of the sub-projects undertaken by the construction team. Quality inspection personnel at all levels are technicians with rich construction experience and professional titles, familiar with specifications and drawings, and rigorous work.
(3) Set quality objectives, with the qualified rate of subdivisional work 100% and the excellent rate of unit project.
More than 85%.
(4) Seriously implement the technical specifications and obey the work instructions of the supervision engineer to satisfy the supervision engineer.
⑤ Carry out total quality management activities and establish quality responsibility system. Control the construction technology and raw material quality.
⑥ Strengthen measurement and test work. Adhere to the process quality self-inspection system. After each process is completed, the process self-inspection shall be carried out. If the previous procedure is unqualified, the construction of the next procedure is not allowed. After passing the self-inspection, report to the supervision engineer for inspection and appraisal.
⑦ Carry out QC activities, select hardcover formwork technology, steel skeleton hoisting technology, continuous beam cast-in-place technology and prestress technology as the key research topics to create excellence, implement on-the-job training, carry out QC competition activities during construction, break through technical difficulties and ensure quality success at one time.
Today, the project department will organize the project quality inspection on a monthly basis, and strictly implement the quality one-vote veto in the work inspection and valuation.
3, safety assurance measures
① In the construction process, implement the principles of "safety first, prevention first" and "safety must be managed and production must be controlled". The Project Department set up a "Safety Production Management Committee" headed by the Deputy Manager, and equipped full-time safety production cadres to take charge of daily safety production. The construction team accordingly set up a "safety production leading group" composed of part-time safety production cadres. (2) Before the project starts, according to the characteristics of the project, the topography, geology, hydrology, meteorology and other data of the construction area, the corresponding safety technical measures shall be formulated while compiling the construction organization design. (3) Personnel participating in the construction must receive safety technology education, raise awareness of safety production, be familiar with and abide by various safety operation procedures of this type of work, and conduct regular safety technology assessment. Only those who pass the examination can operate at their posts.
(4) Set safety production targets, strictly control safety accidents, and put an end to heavy casualties.
The rate of minor injuries should be controlled below 1‰.
⑤ Civilized construction. The construction site should be kept clean and tidy, materials and equipment should be stacked in an orderly manner, and construction roads and drains should be unblocked. Eye-catching safety production slogans are hung on the construction site, and safety operation procedures are erected beside various machines. Frequently carry out safety production knowledge competitions. 6. Operators must wear protective equipment according to regulations before taking up their posts.
⑦ The living and production houses, concrete mixing stations and temporary houses on the construction site should be well protected against fire, flood and theft.
(8) Organize a major inspection of production safety at least once a month, put forward and implement corrective measures immediately when potential accidents are found, and adhere to the "three-no-misses" for safety accidents caused by violations, that is, do not let go until the cause of the accident is found out; The person in charge is not clear about it; Don't let go without corrective measures.
Pet-name ruby after entering the beam construction, all aerial work, so to strengthen the safety education of construction personnel, workers must be in strict accordance with the safety operation procedures for construction, to prevent illegal operations. Attending to make a significant contribution in the work of production safety, give praise and reward, for repeat offenders, serious education and punishment. Six, beam construction period arrangement
The construction period of the superstructure of the main bridge is arranged on the premise of ensuring the total construction period, and the influence of rain, climate and other factors is considered. , maximize the use of scaffolding materials and templates, each cycle construction period is 90 days, interspersed with ancillary facilities. See the time schedule of superstructure for the total time limit for a project.
Schedule of superstructure construction period
Seven. Labor force plan
Entering the beam construction is also a period of relatively concentrated labor force. According to the construction period, the reasonable allocation of labor force is a necessary condition for the smooth progress of the project. The superstructure construction will be arranged in three shifts, and each support will be equipped with a professional construction team. Each team of bridge operators shall be equipped with 120 people.
VIII. List of main machines and materials for beam construction
(1) Host computer
(2) Main materials
Nine. attached drawing