Chapter I Compilation Description

I. Basis for compilation

1. 1, two-stage construction design of expressway (Volume I Bridge) contract section.

1.2, Technical Standard for Highway Engineering (JTG B01-2003);

1.3, Technical Code for Construction of Highway Bridges and Culverts (JTJ 04 1-2000)

1.4, Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts (JTG D62-2004);

1.5, Standard for Quality Inspection and Evaluation of Highway and Bridge Engineering (JTG F80/ 1-2004)

1.6, Technical Code for Construction Safety of Highway and Bridge Engineering (JTJ 076-95)

2, the preparation principle

2. 1, in line with the principle of high quality, high efficiency, economy and rationality, and based on the documents and technical design drawings provided by the owner and the supervisor, strictly implement the relevant construction technical specifications of highway and bridge engineering.

2.2, in order to ensure the construction period and appropriate in advance as the principle, arrange the construction progress.

2.3, to ensure the quality goal as the principle, arrange professional construction team, equipped with advanced machinery and equipment, using advanced construction methods.

2.4, to ensure safety in production as the principle to develop various safety measures, strictly implement the safety operation procedures.

2.5, in order to save land, protect the ecological environment as the goal of the construction general layout.

Chapter II Project Overview

The superstructure of viaduct is designed as prestressed concrete T-beam, which is simply supported first and then continuous. The left line spans 7 spans and the right line spans 8 spans, with 5 T-beams per span, * * * m (7+8)*5=75 T-beams. The height of T-beam is 2.0m, the spacing between main beams is 2.4 m, and the precast width is center beam 1.7m, side beam 2. 1.30m, main beam rib 0.20 m and horseshoe 0.5m.

Chapter III General Arrangement

T-beam prefabrication yard is planned to be located on K3+5 15.0 ~ K3+675.0 subgrade (see Plan of 30mT-beam prefabrication yard for viaduct). There is a 12 prefabricated pedestal in the yard, storage and blanking areas for steel strands and coils at both ends, and corrugated pipe storage area on the left side of the line. Equipped with a gantry crane (2 sets) (span 24m, clear height 1 1m), center beam formwork 1 set and side beam formwork 2 sets.

Chapter IV Construction Scheme

First, the foundation treatment

For T-beam prefabrication site, the foundation is required to have sufficient bearing capacity and stability to avoid uneven settlement during T-beam prefabrication.

The prefabrication yard is located on the subgrade of the main line, and the compaction degree of subgrade filling meets the design and specification requirements.

C25 concrete foundation with a height of 35cm and a width of 100cm is poured under each precast base to improve the overall stiffness and stability of the base. A proper amount of steel bars shall be embedded in the top surface of the base and chiseled to ensure the firm bonding between the base and the pedestal.

Considering that the T-beam arches upward and is simply supported after tension, the two ends of the base will bear considerable local pressure. In order to avoid uneven settlement of the foundation, a reinforced concrete foundation with a height of 2m (length) × 1.5m (width )× ×0.6m is set at both ends of the foundation (see the cross section of 30mT beam precast yard).

Vertical and horizontal drains are set in the prefabrication yard to ensure smooth drainage and no water accumulation during prefabrication.

Second, the base setting

There are 2 rows of prefabricated pedestals in the prefabrication yard, 6 in each row, totaling 12 (8 center beam pedestals and 4 side beam pedestals). The center beam base is 30.0m long and the side beam base is 30.2m long and 50cm wide, which is consistent with the length of T beam and the width of horseshoe.

Because the T-beam is in tension, the concrete will shrink and creep, and it will produce an upper arch. According to the construction experience and design requirements, a pre-inverted arch of 3.0 cm downward is set in the middle of the base span, and the pre-camber of the beam end is zero according to the quadratic parabola.

The prefabricated base is made of C25 reinforced concrete, and the top surface is paved with 8mm thick steel plate. The top surface of the whole base should be smooth enough and straight, and can't turn along the long direction. The two sides of the top surface are buried with [5.0] with outward openings. Before the T-beam is assembled, a rubber tube is built in the channel steel, and the elastic compression of the rubber tube by the side formwork can prevent the bottom plate from leaking slurry. (See schematic diagram of precast base of 30mT beam)

PVC pipes with an inner diameter of 5cm are pre-embedded in the prefabricated base, and one pipe is arranged at intervals of 90cm along the length direction of the base, which is used as the bottom pulling screw for T-beam formwork installation.

The hoisting of T-beam is considered according to the bottom hoisting method of pocket beam, so the movable joint steel plate required for cable threading is reserved on the base, and the clear distance of movable joint is 25cm.

Three, steel processing and installation

1. Processing of ordinary steel bars

A) Each batch of steel arriving at the construction site shall provide the resident supervision engineer with the manufacturer's test report and ex-factory quality assurance certificate. And according to different types, grades, brands and manufacturers, they are classified and piled up, and listed for identification.

B) Before formal welding, all steel bars (especially stressed steel bars) must be carefully welded as required, and welding can be carried out only after passing the requirements.

C) Steel bars shall be straightened and derusted before use to ensure that the steel bar surface is clean and straight without local bending.

D) The processing and manufacturing of steel bars shall be carried out in the processing shed in strict accordance with the design drawings, and the bending and welding of steel bars shall be carried out in strict accordance with the specifications.

2. Processing of prestressed tendons

A) When the prestressed steel strand is stored on site, the ground should be raised by more than 20cm, and temporary open-air stacking must be stamped.

B) Check the appearance quality of steel strand, and timely correct the disorder, kink and pricking of steel strand; If cracks, small thorns, mechanical damage, dead bending, etc. are found, they should be partially removed. If brittle fracture and splitting are found, the material must be reflected in time and re-inspected.

C) The steel strand is cut by disc cutter, and its blanking length should meet the design requirements and the needs of tensioning operation (considering the working length of tensioning end is 60cm).

D) The steel strand is bound into a bundle with 18# iron wire, and the binding spacing is1.5m. Each end is 5 ~ 10 cm away from the end, and the two ends of the bound steel strand are aligned, and the number should indicate the length and use position of the steel strand.

E) When storing the braided steel strand bundle, the lower part must be padded with a cushion with a height of not less than 20cm.

3. Reinforcement installation

A) Before steel bar binding, check the steel bar ingredient list and material card, and then conduct steel bar binding after the diameter, shape, size and quantity are correct.

B) During installation, the order of inserting steel bars in place and the mutual cooperation with formwork and steel hinge lines should be considered to reduce the installation difficulty. Steel bars shall be paid out before installation and installed in sequence.

C) When installing steel bars, concrete blocks of the same grade as the beams should be added at appropriate positions to ensure the thickness of the protective layer of steel bars.

D) Set reliable supports on both sides of the steel bar to prevent the steel bar from overturning and hurting people.

E) Bury the bearing steel plate at the bottom of the beam rib, and adjust the steel plate slope according to the designed longitudinal slope to ensure the T-beam.

After the erection is completed, the top surface of the bearing is horizontal and closely adheres to the embedded steel plate at the bottom of the beam.

F) Each corrugated pipe shall be provided with pound-shaped positioning reinforcement along the length direction of the pipe. One positioning steel bar is arranged every 50cm, and the tangent section of steel beam is encrypted to 30cm. All positioning steel bars shall be fixed on the ordinary steel bars of the beam. Bellows are connected by joint bellows and wrapped with black tape to ensure that the joint does not leak slurry.

G) When the position of prestressed pipeline conflicts with the position of steel bar, the position of steel bar should be adjusted appropriately to ensure the accurate position of prestressed pipeline.

H) When binding the roof steel bar, attention should be paid to embedding the anti-collision railing steel bar, embedded parts of beam end expansion joints and drain holes.

I) Handle the connection between corrugated pipe and anchor pad, and install grouting pipe correctly. Take necessary measures to protect the grouting pipe. The installation position of anchorage should be accurate, the bearing surface of anchor pad and the installation surface of anchor ring must be perpendicular to the tunnel centerline, and the anchorage centerline must coincide with the tunnel centerline.

J) The steel strand shall be directly inserted manually. Before threading, the front end of the steel strand should be wrapped with black tape to avoid damaging the bellows. During threading, when the steel strand ends are close to the nozzle, the steel strand should be lifted in time and slowed down so that all the steel strand ends can enter the pipe. After crossing the beam, check the steel strand pipes one by one. If the bellows joint is found to be damaged or loose, it should be repaired in time. Confirm before entering the next process.

Four, template processing and disassembly

1. Template design and processing

3 sets of T-beam formwork are made in the prefabrication yard and processed by professional formwork manufacturers. In addition to meeting the design requirements of strength and flatness, template processing should also consider the convenience of template installation and disassembly, and at the same time, T-beam should be equipped with attached vibrator support at the best position. T-beam side formwork shall be made in blocks according to the position of diaphragm. In order to ensure the beauty of the beam, only two rows of opposite pulling screws are arranged, and there are no opposite pulling screws in the beam. After the template processing is completed, pressure test shall be carried out on the pedestal, and its size, flatness and other indicators shall be accepted, and it can be delivered only after it is qualified. Attention should be paid to when processing:

A) The length and size of segments (segment length and assembly length) shall be accurate;

B) Formwork should be straight, corners should be smooth, and welds should be smooth;

C) The positions of bolt holes connected between the mold fans shall be accurate;

D) The bottom angle of the formwork shall be straight and the height of the top surface of the formwork shall be accurate;

E) The pre-reserved hole position of the end formwork prestressed channel is accurate;

F) Angle steel holes shall be used for connection.

2. Template assembly and disassembly

The lifting, installation and removal of formwork are completed by the construction truss vehicle located in the prefabrication yard. Before the mold is installed, clean its surface and apply template paint evenly. Molding should be carried out from one end to the other in the order of transverse symmetry and longitudinal direction. Dismantling of formwork jack the formwork from the concrete. Attention should be paid to when loading and unloading templates:

A) The formwork shall be carefully maintained during use and kept in good condition throughout the construction process;

B) When assembling the formwork, ensure that the formwork joints are smooth and tight, and do not leak slurry;

C) Formwork shall be inspected during installation and concrete pouring to prevent formwork removal from being difficult due to deformation;

D) It is forbidden to use oxygen to cut the template, so as to avoid collision during loading and unloading;

E) In order to prevent concrete cracks and corner damage, the formwork can only be removed when the concrete strength reaches more than 3MPa.

Verb (abbreviation of verb) concrete pouring

The concrete mixture ratio of T-beam is determined by the laboratory. When pouring concrete, it is transported by concrete tanker, poured by gantry crane with bucket, and vibrated by combining attached vibrator and plug-in vibrator. T-beam concrete is continuously poured horizontally in layers. The pouring method is as follows:

A) The pouring direction is pushed from one end of the beam to the other end in sequence. When approaching the other end, in order to avoid uneven distribution of aggregate in the concrete at the beam end, it should be fed from the other end in the opposite direction and closed at a distance of 4 ~ 5 m from the end.

B) Layered blanking and vibrating, with the thickness of each layer not exceeding 30cm. The pouring time of the upper and lower layers shall not exceed 1 hour (when the temperature is above 30℃) or 1.5h (when the temperature is below 30℃), and the upper layer shall be mixed.

Concrete can only be poured after the lower concrete is vibrated and compacted, so as to ensure the good compactness of concrete.

C) The horseshoe-shaped part of the T-beam has concentrated steel bars and prestressed pipes. In order to ensure the quality, the horseshoe-shaped part can be poured first, and then the web plate can be poured. The partition and web shall be poured at the same time, and the pouring shall be carried out in parallel in stages.

D) In order to avoid the longitudinal cracks caused by the sinking of the web concrete at the joint between the abdomen and the wing plate, it can be stopped for a period of time after the pouring is completed, so that the web concrete can fully sink, and then the flange plate concrete can be poured. However, it is necessary to ensure that the wing plate concrete is poured before the web plate concrete is solidified, and the concrete is leveled and collected in time.

E) When pouring T-beam concrete, special attention should be paid to the vibrating of concrete. Vibrating shall be carried out by special personnel, and the attached vibrator shall be used in combination with the internal vibrator. The attached vibrator shall be used for vibrating below the corrugated pipe, and the internal vibrator shall be used for vibrating above the corrugated pipe.

F) There are many embedded parts and steel bars in the prestressed anchorage, so special attention should be paid to the compactness of concrete, and vibrating should be done carefully. Small aggregate concrete can be used when necessary.

G) The mixing quality and slump of concrete should be strictly controlled during construction. At the same time, in order to improve the working performance of T-beam concrete, the effective components of water reducer can be properly adjusted according to the temperature during construction, so that the setting time and waiting time of concrete can meet the construction needs.

Six, concrete curing

After concrete pouring is completed, cover geotextile for curing immediately, and the curing time is 7 days. During the curing period, the concrete should always be in a wet state. When the temperature is lower than 5℃. C, cover the greenhouse with steam for maintenance.

Seven, the tensioning of prestressed steel beam

Prestressed steel beams of precast T-beams can not be tensioned until the concrete cube strength reaches 90% of the concrete design strength grade and the concrete age is not less than 7 days. The tensioning sequence is 0→ 10%σk (the initial stress value is marked as elongation) →20%σk→ 100%σk (holding load for 2min, measuring elongation) → anchoring (σk is design tension), and corresponding tensioning records shall be made at the same time. Both ends of the positive moment steel beam in the precast beam and the negative moment steel beam in the pier top continuous section are tensioned at the same time, and the control stress under the anchor is 0.75fpk= 1395Mpa.

Construction prestress should be controlled by tension and elongation. When the prestressing tendon reaches the design tension, the error between the actual elongation and the theoretical elongation should be controlled within 6%. Inelastic deformation of steel beams should be deducted from the actual elongation.

Measures must be taken to prevent the beam from bending laterally when tensioning the prestressed steel beam of the main beam. Tension sequence: 50% N2 →100% n3 →100% N2 →100% n1.

According to the maximum tonnage of prestressed tensioning, 250T through-hole jack is selected as tensioning equipment.

1. General requirements

The tensioning device should be calibrated. After the jack has been used for more than 6 months or 200 times, or abnormal phenomena occur during use, it should be recalibrated. The accuracy of the pressure gauge shall not be lower than 1.5. There should be safety measures when tensioning prestress, and no one should stand after tensioning jack.

The tensioning operation adopts the principle of double control: that is, double control of stress and elongation. When the tensioning reaches the design tonnage, the allowable error between the theoretical elongation and the actual elongation of all prestressed tendons should be within 6% of the theoretical elongation, otherwise the following measures should be taken:

A. recalibrate the equipment

B, testing the elastic modulus of prestressed materials.

C. relax the prestressed reinforcement and re-tension.

The initial tension is 10% tension, which is to tighten the slack prestressed steel bar. At this time, the jack should be completely fixed. After tensioning the slack prestressed steel bar, accurately mark the two ends of the prestressed steel bar, measure the elongation of the prestressed steel bar from this mark, and mark each prestressed steel strand to observe whether there is slippage. When tensioning, both ends shall be tensioned synchronously, symmetrically and evenly.

After the prestressed steel strand is tensioned, the deformation of the prestressed anchorage should be measured. For the clip anchorage, it should not be greater than 6mm. If it is greater than the above allowable value, it should be re-tensioned, or re-tensioned after replacing the anchorage.

The broken wire and slippery wire of prestressed steel strand shall not exceed the specification. If it exceeds the limit, it should be replaced.

When calculating the elongation, the elastic modulus should be determined according to the sample or test certificate.

2. Tension step:

Insert the working anchorage into the steel beam and drive the clamping piece to tighten it, then insert the limit plate, jack and tool anchor in turn, and finally start tensioning after installing the tool clamping piece. Firstly, it is stretched to 10% of the design tonnage, and its elongation is measured; Second, stretch it to 20% of the design tonnage and measure its elongation. Then stretch to 100% of the designed tonnage, keep the load for 2 minutes, and measure the elongation. Finally, the jack returns oil to the anchor, and the force is transferred from the tool holder to the work holder to complete the tensioning. The tensioning sequence is as follows:

0→ initial stress (10%бcon)→ initial stress (20%бcon)→ 100%бcon (measure elongation, anchor with load for 2min).

Elongation l = (l100%-l10%)/0.9–δ (retraction value)

Eight, T beam prestressed grouting

1. Preparation before grouting

Cut the steel strand outside the anchorage with a disc cutter, and cool it with water in time after cutting, so as to prevent the steel strand and anchorage from overheating and causing the steel wire to slip.

Fill the gap between anchorage and steel strand with cement slurry to avoid losing grouting pressure due to slurry leakage, but ensure that grouting holes and exhaust holes of anchorage are unblocked.

Before grouting, flush the hole with pressurized water to remove impurities such as powder and slag in the hole to ensure smooth flow in the hole. After washing, blow out the accumulated water in the hole with an air compressor, and then grout it in time. When the phenomenon of string holes is found and difficult to handle, the number of string holes should be determined, and several string holes should be injected at the same time during grouting.

2. Mixing of cement slurry

The mixture ratio of cement slurry is determined by the laboratory, and the appropriate water cement ratio is 0.40~0.45. The age of all cement shall not exceed one month, the maximum bleeding rate of cement slurry shall not exceed 3%, and the bleeding rate shall be controlled at 2% 3 hours after mixing.

Water reducing agent can be added to cement slurry mixture, and its dosage is determined by experiments. The water-cement ratio of cement paste mixed with water reducer can be reduced to 0.35. Mixtures containing chlorides and nitrates should not be used.

Appropriate expansion agent can be mixed into cement slurry (through the test), and the performance and use of expansion agent conform to the Technical Specification for Application of Concrete Admixtures (GBJ 1 19-88). After adding expansive agent, the unconstrained free expansion of cement slurry should be less than 10%.

When mixing cement slurry, water should be added to the mixer first, then cement should be added. After thorough mixing, add additives. Water in admixture should be included in water cement ratio. Stir for at least 2 minutes until a uniform consistency is achieved. Any one dose is enough for one hour's use. The consistency should be controlled between 14- 18s.

The bleeding rate, swelling rate and consistency of the cement slurry are tested according to Appendix G- 10 and G-1/in Technical Specification for Construction of Highway Bridges and Culverts (JTJ04 1-2000).

3. Grouting

During grouting, each working class shall take no less than three groups of samples (three cube specimens of 70.7mm×70.7mm×70.7mm in each group) for standard curing for 28 days, and check their compressive strength as the evaluation basis of cement slurry quality.

When the air temperature or component temperature is lower than 5℃, grouting is not allowed. The temperature of cement slurry shall not exceed 32℃.

Pipe grouting should be carried out as soon as possible after the tensioning of prestressed steel strand is completed, generally not exceeding 14d.

In general, the time from preparation of cement slurry to injection channel should not exceed 30-45 minutes, and the cement slurry should be stirred frequently during injection before use.

Pipes filled with mud shall be protected from vibration within one day. Within 48 hours after the slurry is injected into the pipeline, the temperature of structural concrete shall not be lower than 5℃, otherwise heat preservation measures shall be taken. When the temperature is higher than 35℃ during the day, grouting should be carried out at night. Two days after grouting, check the compactness of cement slurry at the injection end and the gas outlet, and treat or replenish pressure if necessary.

After grouting, complete grouting records shall be kept, including grouting date, water cement ratio and admixture, grouting pressure, strength of test block, details of obstacles and accidents, and work to be completed.

Nine, the end seal

Immediately after the hole grouting, the cement slurry at the beam end will be washed clean, and at the same time, the dirt on the anchor pad, anchorage and end face concrete will be removed, the end face concrete will be chiseled, and the end steel mesh will be bound. After assembling the end formwork and vertical formwork, check the full length of the beam, fix the formwork and pour the end concrete.

Due to the large number of end-sealing steel bars and small space, it is necessary to operate carefully and vibrate carefully to ensure the concrete at the anchorage is dense.

Ten, moving beam and beam.

① hoisting

According to many years' construction experience and practice, my project department adopts two sets of 75T gantry cranes for bottom lifting, and the two ends are lifted horizontally and symmetrically. When prefabricating the beam, the movable joint bottom formwork required to penetrate the cable bottom shall be reserved about 80cm away from the end of the base. Short beams are set at the top and bottom of the beam, φ 32 thin steel bars are used as slings between the short beams, and lifting rings are set on the top beam, and the hook on the crane can be lifted after being buckled with the lifting rings. Both sides of the sling are filled with cork boards (or thick rubber) to protect the solid concrete.

② Walking.

Gantry crane walking track should be firm, smooth, no triangle pit, gantry crane should walk slowly. Operators have a unified password, drivers hold relevant certificates, are familiar with the operating procedures, and operate according to the signal of the commander. The four corners of the gantry crane are guarded by special personnel, and there are at least two iron shoes and triangular wood on both sides.

③ save the beam

Stored in a planned way according to the number, which is convenient for taking the beam when erecting the beam. All beams are stored in a single layer, and the two ends of the beams are provided with firm storage brackets, and the beams are not directly stored on the ground, so as to avoid cracking or even fracture of the upper part of the beams due to stress on uneven ground. Do a good job of drainage in the beam storage area to prevent surface water from washing the ground and causing subsidence.

Chapter V Personnel Arrangement and Progress

In order to ensure the construction quality and progress, the chief engineer will be the technical director of the project department, responsible for on-site production and technology, and closely cooperate with various functional departments, carefully organize and scientifically arrange.

Construction plan arrangement: the prefabrication yard of this contract section is scheduled to start on, and T-beams will be prefabricated on, and all beams and slabs will be prefabricated on.

Chapter VI Safeguard Measures

A, engineering quality assurance measures

1. Quality assurance measures for steel processing and installation

A. the mechanical properties of steel bars must meet the specification requirements. Check the factory certificate and conduct spot checks.

B. Steel bar welding: The operator must hold relevant certificates, and the welding head can only be formally operated after passing the examination. Random sampling inspection of a batch of weldments is carried out to strengthen the supervision and assessment of welding quality.

C. After the steel bar binding is completed, the formwork and concrete can be installed only after the acceptance of the supervision engineer. In the process of concrete pouring, the steel bar worker must be on duty to deal with the problems of steel bar and embedded displacement in the construction process.

2. Template quality assurance measures

Formwork design should take into account that the formwork has sufficient strength, rigidity and stability, can bear all kinds of loads that may occur in the construction process, and ensure that the shapes and sizes of various parts of the structure are accurate and simple to manufacture. Template joints tightly, do not leak slurry. It is particularly important to note that after the formwork is removed, the concrete structure should have a smooth surface, straight lines and no deformation or warping. The curve part should be smooth and meet the design requirements.

B. After the formwork is manufactured, try to spell it, and its plane size, verticality and flatness meet the specification requirements. Implement three-level acceptance procedures.

C before each installation, the surface of the formwork shall be decontaminated and derusted, coated with release agent, and installed according to the trial assembly procedure. After the template is adjusted, please ask the supervision engineer to retest for approval, and concrete pouring will be carried out after the structural supervision engineer agrees.

3. Concrete quality assurance measures

A. Quality assurance of concrete raw materials

○ 1 cement must have a factory test report when it comes into play. If there are doubts about the quality of cement, or the requirements of the supervision engineer, or the storage period of cement exceeds three months, the cement should be reinspected and tested.

2 Before using sand and gravel materials, an investigation should be conducted to select suppliers who can guarantee the supply and supply quality, and their quality should be sampled and inspected according to the requirements of the specification. Anyone who does not meet the requirements is not allowed to enter the construction site.

○3 The chemical analysis of water shall be carried out according to the Operating Rules for Water Quality Analysis of Highway Engineering (JTJ056-84).

○4 Before using the admixture, there should be the product inspection certificate and other relevant information, and the use of the admixture should comply with the Technical Specification for the Application of Concrete Admixtures (GBJ 1 19-88).

B. Concrete mix design

Design the concrete mixture ratio in strict accordance with the provisions of the mixture ratio design to ensure the measurement of concrete components and the mixing, transportation, pouring and maintenance of concrete mixture. According to the strength requirements of concrete, accurately calculate the concrete mixture ratio and report it to the supervision engineer for approval. It can only be used after the supervision engineer agrees. In the process of use, the design mixture ratio should be strictly implemented.

C. Measurement of concrete raw materials

Each plate of concrete members must be weighed by electronic scales, and the measuring equipment should be calibrated. In the process of construction, the moisture content of aggregate should be determined according to the weather change, and the water consumption should be adjusted in time according to the test results.

D. Mixing of concrete

Concrete mixture should have the same color, and there should be no segregation and bleeding. The shortest time for concrete mixing shall conform to the national standard Code for Construction and Acceptance of Concrete Structure Engineering. The strength of concrete mixture shall be sampled and tested at the mixing place and pouring place respectively, and each workbench shift shall be no less than three times.

E. concrete transportation

In the process of transportation, it should be controlled that after the concrete is transported to the pouring site, it will not segregate or delaminate, and its composition will not change, so as to ensure the consistency required for construction.

F. Concrete pouring

After the concrete arrives at the site, slump test must be carried out, and it can be poured only after it meets the requirements. If the slump loss is too large, the tester can obtain the consent of the supervision engineer according to the actual situation, and then add an appropriate amount of cement slurry to ensure that the water-cement ratio of concrete remains the same, and can only pour after mixing evenly. When vibrating concrete, choose the appropriate vibrator according to the construction object and the nature of concrete mixture, and determine the vibrating time. In the process of pouring and standing, measures should be taken to prevent cracks

G. Maintenance of concrete structures

In the curing process, concrete should be controlled in a temperature environment conducive to hardening and strength growth. Different curing methods should be adopted according to the construction object, environment, cement varieties, additives and performance requirements of concrete.

Second, the time limit for a project guarantee measures

According to the actual situation, in order to ensure the construction period, our department will take the following measures to ensure the construction period:

1. Organize relevant personnel to be familiar with the design drawings seriously, so as to control the whole construction process and quality;

2. Prepare a reasonable construction schedule and construction organization design, and equip the site with technology and construction personnel with rich construction experience to organize the construction, so that the construction process can be carried out in an orderly manner;

Third, safety assurance measures

In the whole process of implementing and completing this project, our company will take practical and effective measures to fully guarantee the safety of all personnel and make the implementation of the project orderly and smoothly.

1, strengthen safety education for workers and migrant workers, establish the idea of safety first, and raise safety awareness. The project manager department will set up a "safety leading group", with the project manager and deputy manager as the team leader and deputy team leader, and equipped with full-time security officers to be responsible for the safety management in the construction process. The management department shall regularly organize the team leader to conduct inspection and appraisal, and those that do not meet the safety requirements shall be rectified within a time limit until the work is stopped and rectified, and the construction can continue only after passing the inspection.

2, formulate the operation procedures of each process and post safety in production, and put up notices to regulate the production activities of workers and migrant workers.

3, often check the construction equipment, strengthen the maintenance, to ensure that the equipment is always in good condition during the whole construction period.

4, equipped with the necessary transportation and communication facilities, strengthen the ability to deal with unexpected accidents.

5. Set full-time electrician to be responsible for the installation and inspection of various electrical facilities within the construction scope. At the same time, necessary safety protection and electricity use warning signs are set to ensure the safety of electricity use.

6, the use of hoist, crane and other equipment construction, by specialist command, specialist operation, attention should be paid to the safety of ground personnel and machinery.

7, the construction site electricity safety measures

1) The construction site shall formulate detailed construction electricity organization design, and at the same time formulate electrical safety operation procedures, electrical installation procedures, electrical operation management procedures and electrical maintenance inspection system.

2) The electrical equipment on the construction site meets the requirements of Technical Specification for Temporary Electrical Safety on the Construction Site (JC46-S8) of the Ministry of Construction, and the wires (cables) are erected as required, without dragging anywhere.

3) The power transformation and distribution room shall meet the requirements of "Four Preventions and One Prevention", establish corresponding management system and configure necessary safety protection articles.

4) Hand-held electric tools and small electrical equipment should be managed by special personnel. Electrical equipment entering and leaving the warehouse should be carefully inspected and accepted, and daily inspection, repair and maintenance should be done. Running with illness is not allowed.

5) Electrical workers must wear personal protective equipment, strictly implement electrical safety operation procedures, and hold relevant certificates.

8, prestressed concrete beam

8. 1, prestressed concrete construction requirements

(1) tensioning operation area, irrelevant personnel are not allowed to enter;

⑵ Check whether the tensioning equipment and tools (such as jack, oil pump, pressure gauge, tubing and hydraulic top valve) are in good condition. ) meet the requirements of construction and safety, and the pressure gauge shall be marked periodically as required;

(3) The anchor ring and anchor plug can only be used after passing the inspection before use;

(4) The connection point and interface between the high-pressure oil pump and the jack must be in good condition, and the oil pump operator should wear protective glasses;

8.2 Before tensioning, check the pedestal, beam, etc.

8.3, at the end of the prestressed steel tensioning, no one can stand on the jack.

8.4, steel tension or cold drawing, screw end, sleeve screw must have enough length; The fixture should have sufficient fastening capacity to prevent the anchor clip from slipping out due to looseness.

8.5 Abnormal conditions (such as violent vibration of oil gauge, oil leakage, abnormal motor sound, broken wires and slippery lines, etc.) occur during tensioning operation. ), immediately stop the machine for inspection.

8.6 After the steel beam is tensioned, safety protection measures should be taken when pulling out the pin. When removing the pin manually, it is forbidden to slam.

8.7 After tensioning, both ends of tensioning anchorage shall be properly protected, and no heavy objects shall be pressed. Before the pipeline grouting, the beam end shall be provided with fences and baffles. It is forbidden to hit the anchorage, steel beam and steel bar.

8.8, pipe grouting, should be carried out in strict accordance with the provisions of pressure. The safety valve should be adjusted before construction. When closing the safety valve, the operator should stand on the side.

Fourth, environmental protection measures.

In the whole construction process, strictly abide by the relevant provisions of the state, provincial and municipal environmental protection departments on environmental protection, earnestly abide by the specific requirements of the bidding documents on environmental protection, and do a good job in environmental protection during the operation period and construction period. The following measures will be taken:

1. Most prefabricated sites are set within the red line, so as to minimize land acquisition and reduce the impact on the production and life of local residents;

2. Try to avoid construction at night for noise operation, so as not to affect the normal rest of local residents;

3. The prefabrication yard is provided with a sewage sedimentation tank, and the production sewage (such as cement slurry) is discharged to the designated area after sedimentation;

4. Production and living garbage should be piled up in the designated area within the red line for centralized treatment.

FYI