I. Basis for compilation
1, according to the design drawings of XXXXX bid section;
2. According to the current design specifications, construction specifications, acceptance standards and other relevant documents of the Ministry of Railways and the Ministry of Communications.
3. The railway department has implemented mature construction methods.
4. Relevant field investigation data and hydrogeological investigation data.
5, engaged in similar railway engineering construction experience, technical summary and existing construction strength and mechanical equipment, equipment.
Second, the frame bridge construction
1, construction preparation
According to the requirements of engineering design documents, select the formwork (wooden formwork or steel formwork) suitable for this project for formwork design, and calculate the corresponding load according to the requirements of the Code. When designing the formwork, the geometric dimensions of the formwork should meet the requirements of the design documents, and ensure the accuracy of the corresponding positions of various parts of the structural members. The formwork itself and the supporting system should be calculated to have sufficient strength, rigidity and stability, and can bear the concrete load and construction load reliably without damage or deformation beyond the quality requirements.
When selecting the template, the structure and splicing connection of the template should be convenient for installation and disassembly for reuse.
After the template engineering design is completed, the design technicians shall make technical disclosure to the professional template production team. The disclosure mainly includes the following points:
(1) Engineering object, template quantity and task completion time.
(2) Template assembly, support system layout, node treatment, embedded parts, reserved holes and steel dowel treatment methods.
(3) Template production quality and safety measures.
(4) For specially designed structural members, draw the template structure diagram and installation contact structure diagram, and cooperate with the template team to draw details on the template.
After technical disclosure, the template team should also be familiar with the template design drawings carefully, and prepare for the division of labor and materials for template construction.
2, the construction method
2. 1, template making
Large steel formwork can be ordered from manufacturers meeting national standards, and the purchasing personnel should strictly control the quality of incoming goods and control them according to the requirements of program documents.
In the production of wooden formwork, firstly, wood with appropriate thickness is selected and processed into required plates and square materials, then the formwork is laid out and made according to the design drawings, and the formwork is assembled on site, which can only be transported to the construction site after meeting the design requirements. For complex structures, small models can be made according to the design drawings, and after being confirmed by technicians, detailed drawings will be released on the templates, and skilled technicians will process them according to the requirements of specifications. After processing, it must be assembled first and then transported to the construction site after meeting the design requirements.
Quality requirements for making templates:
(1) Ensure that the design shapes, sizes and positions of concrete structures and components are correct.
(2) The formwork must have sufficient strength, rigidity and stability to withstand the gravity, lateral pressure of newly poured concrete and various loads that may be generated during construction.
(3) Formwork flat-fell seam should be tight, the gap should not be greater than 1mm, and it is simple to manufacture, convenient to install, easy to disassemble and reusable.
(4) It can adapt to the characteristics, construction conditions and pouring methods of concrete structures and members.
(5) The surface of the formwork shall be smooth without unevenness, and the staggered joints of the formwork splicing steps shall not be greater than 2mm.
2.2, steel production
(1) steel bar fabrication
Steel bars are processed in the steel bar processing site, and the steel bars are cut in batches according to the design size requirements of the frame culvert, and the length of the welded joint of the steel bars to be welded is included in the cutting. Steel bar should be straightened before bending, and oil stains, paint stains, cement slurry, peeling and rust on the surface should be removed. Steel bars shall be straight without local bending. There should be no scars on the surface of the processed steel bar that weaken the cross section of the steel bar, and the bending and hook at the end should meet the design requirements. Bending reinforcement should start from the middle and gradually bend to both ends, and the hook should be bent at one time.
The allowable deviation of reinforcement processing shall not exceed the following table:
Allowable deviation of serial number name (mm)
1 The total length of reinforcement along the length direction is 10.
2 The bending position of bending steel bar is 20.
(2) Reinforcement joint treatment
Welded joints of steel bars shall ensure that the number of joints in the same section does not exceed 50% of the total number of steel bars in this section, and the positions of adjacent joints shall be staggered by more than 50cm.
Steel bar joints are generally welded and bound with iron wires. Flash butt welding or arc welding should be adopted for welding, with flash butt welding as the main method. Welded joints are used for reinforcing steel bars in tie rod parts, regardless of their diameters. The welding technology, welding machine model, welding parameters, welding quality and welder training of steel bar joints shall meet the requirements of the specification. For specific operation, please refer to the rebar welding operation instruction. Welded joints shall meet the design strength requirements, and samples shall be taken for tensile and cold bending tests respectively. The weld is dense, and when the joint is struck with a small hammer, the steel bar makes the same crisp sound as the basic steel.
When welding unconditionally, steel bars with a lap diameter of 25mm or less can be bound. The lap length of binding joints (calculated from the tangents at the ends of two hooks) should not be less than the specification requirements, and the joints should be set in places where the stress on steel bars is small, and should be distributed to avoid the bending points of steel bars, and the distance from the bending points should not be less than 10d. The welded joints of bent steel bars should not be in the inclined distance section of bent steel bars.
(3) Reinforcement installation
When installing steel bars, the position of steel bars and the thickness of concrete protective layer should meet the design requirements.
The cement mortar pad with the same label as concrete shall be applied between the steel bar and the formwork, and the thickness of the pad shall be less than the thickness of the net protective layer. The cushion blocks shall be staggered into a quincunx arrangement, and shall not span the whole section of the protective layer.
During the transportation, installation and pouring of concrete, the tied and welded steel bars shall not be deformed, cracked and loosened.
Steel binding must be firm and accurate. Reinforced joints should not be in the same plane, and should be staggered according to regulations.
2.3, foundation pit drainage
The drainage methods of foundation pit include ditch diversion, collecting well pumping or well point drainage.
When a drainage culvert is built in a ditch with water flow during construction, a temporary guide ditch should be built at an appropriate position outside the top edge of the culvert foundation pit to discharge surface water. Generally, the drainage in the foundation pit adopts the centralized pumping method of combining the drainage ditch with the collecting well, and the well point method can be used for drainage when the foundation pit is in sandy soil.
2.4, template installation
Before template installation, check the elevation and centerline position of the installation template to ensure that the installation position and elevation of the template meet the design requirements.
The height and width of the template fan depend on the actual situation, and the template is 5cm thick. Veneer fans are made of wooden boards nailed to ribs, with a cross section of 10× 12cm and a spacing of about1m. The connection between the panel and the fan is connected by short rib nails at the rib joints. After the plate is connected with the fan, steel pipe support is added to the outside of the rib. Template in the installation process, should pay attention to flat-fell seam tightly, to prevent slurry leakage. After installation, wash the release agent carefully.
Integral formwork is generally assembled on site. After assembly, the installation sequence of each template shall be numbered. During installation, the templates shall be installed one by one by number. The bottom of the template should be smooth and the joints should be tight. After installation, the release agent must be carefully applied.
2.5, concrete pouring
(1) Check the installation of reinforcement and formwork. Before pouring concrete, all sundries in the formwork must be removed to ensure the quality of pouring concrete.
(2) When pouring concrete, if the height of concrete entering the mould exceeds 2m, it is necessary to transport the concrete into the mould with chute or channel.
(3) The embedded concrete construction must be tamped with an internal vibrator, the moving distance of the internal vibrator should not be greater than 1.5 times the action radius of the vibrator, the depth of embedded concrete should be 50 ~ 100 mm, the vibrating time of each vibrating point should be 20 ~ 30s, and the distance between the internal vibrator and the edge of the template should be10 ~ 650.
(4) Concrete shall be continuously poured at one time as far as possible. If the construction joint is inevitable, the joint reinforcement should be embedded around the joint, the diameter of reinforcement should not be less than 16mm, the spacing between reinforcement should not be more than 20 times of the diameter of reinforcement, and the embedded and exposed length should not be less than 30 times of the diameter.
2.6, template removal
The time for dismantling the formwork shall comply with the provisions of concrete construction and acceptance specifications. Demolition sequence is to dismantle the side formwork first, and then dismantle the bottom formwork for bearing. Temporary supports should be erected when the roof is demolished. For example, when dismantling the whole structure, hang the hanging rope first, and then dismantle the template pin. Removed template connectors should be put into the toolbox, and they should not be thrown around. Dismantled templates shall not be thrown at high altitude, and must be transported to the ground one by one. Demolition of the template should be timely cleaning mortar, and piled up in the designated place. Steel formwork shall be protected against rust.
2.7, construction matters needing attention
(1) When the formwork is installed, the formwork support must be firm and supported on hard rock. It is forbidden to run the formwork during concrete construction.
(2) All formwork shall not be installed with tie rods passing through concrete.
2.8, quality control
(1) All raw materials must be inspected by the supervision engineer before they can be used.
(2) The installation position and geometric dimensions of the formwork must meet the requirements of the design structure, and the construction of the next procedure can only be carried out after passing the "three inspections" and reporting to the supervision engineer for inspection and review.
(3) A set of specimens shall be made for frame bridge concrete every 65,438+000m3, and a set shall be made for less than 65,438+000m3, and each workbench shall be no less than one set. The concrete strength of the specimen must meet the design requirements.
(4) The allowable deviation and inspection methods of each part of the frame bridge are as follows:
Inspection method of allowable deviation (mm) of serial number items
1 Total station with axis offset of 20
2 water level elevation +20 0 water level
3 20-foot aperture quantity inspection
4 Culvert top elevation 15 level
5 culvert length+100-50ft quantity inspection
6. Check the culvert thickness+10 -5 feet.
7 3-foot inspection for staggered joints of culvert body
3, safety, environmental protection and soil and water conservation measures
3. 1, safety measures
(1) If it is a frame bridge for deep foundation pit construction, if sliding cracks are found in the foundation pit during construction, all personnel shall be evacuated in time and the site management personnel shall be informed, and the site management personnel shall take corresponding emergency measures according to the actual situation.
(2) In the construction of frame bridge, every working procedure is completed by a fixed team.
(3) It is forbidden for all personnel to overlap up and down. All staff must fasten their seat belts when working at heights above 2 meters above the ground.
(4) Construction personnel must wear safety helmets, and it is forbidden to wear slippers, go barefoot and work at their posts after drinking.
(5) Safety fences must be set around the foundation pit construction of frame bridge, and the height shall not be lower than 1m, and warning signs shall be set in obvious positions.
3.2, environmental protection and soil and water conservation measures
(1) Take up or avoid forest land and cultivated land as little as possible, protect the original trees and surface vegetation, and take rehabilitation measures for cultivated land within the scope of temporary land use.
(2) The spoil ground should be protected first and then abandoned, so as to prevent silt from scouring and polluting farmland and rivers.
(3) The construction drainage system should be built on the construction site, and it should be unblocked. The waste water in the construction site should be precipitated before discharge, and the necessary purification measures should be taken before discharge. Hazardous substances should be stored in designated places and disposed of according to relevant regulations.
(4) Vehicles that may produce dust should be equipped with baffles and tarpaulins to prevent dust from flying and reduce the harm to production personnel and local residents. Sprinkle water if necessary.
(5) After the completion of the project, clean up the garbage on site in time, and make a civilized exit.