1、 Construction preparation

1. Material preparation: the reinforcement shall have factory certificate and mechanical property inspection report, and all inspection results shall comply with the provisions of current specifications and design requirements. The reinforcement connecting sleeve shall be provided with factory certificate, generally low-alloy steel or excellent carbon structural steel, and its standard value of tensile bearing capacity shall be greater than or equal to 1.20 times of the standard value of the tensile bearing capacity of the connected reinforcement. The length of the reinforcement connecting sleeve shall be twice the diameter of the reinforcement. The reinforcement connecting sleeve shall be provided with a protective cover, and the specification of the sleeve shall be indicated on the protective cover. The reinforcement connecting sleeve shall be protected from corrosion and contamination during transportation and storage. The dimensional deviation and accuracy requirements of the reinforcement connecting sleeve are shown in Table 1.See Table 2 for the outgoing quality inspection requirements of reinforcement connecting sleeve.

Sleeve diameter D outer diameter allowable deviation length allowable deviation thread accuracy

≤50±0.5±0.56H/GB197-81

＞50±0.01D±0.56H/GB197-81

S / N inspection item measuring tool name inspection requirements：

1) The appearance quality shall be visually inspected, and the surface shall be free of cracks and other defects affecting the joint quality

2) The length and outer diameter of external dimension caliper or special gauge shall meet the requirements of the drawing

3) Thread size the through end thread match gauge can smoothly connect the sleeve and reach the screwing length. The stop end thread match gauge is allowed to screw in from both ends of the sleeve, and the screw in amount shall not exceed 3p.

There are four types of commonly used reinforcement connecting sleeves, namely standard sleeve, positive and negative screw sleeve, variable diameter sleeve and adjustable sleeve. The standard sleeve is mainly used for the connection of rotatable reinforcement with the same diameter; The positive and negative screw thread sleeve is used for the connection of reinforcement where the reinforcement at both ends cannot rotate but at least one reinforcement can move axially, such as the construction of turning iron reinforcement; The variable diameter sleeve is used for the connection of reinforcement with different diameters; The adjustable sleeve is used for the connection of reinforcement that cannot rotate at both ends, and also for the connection of reinforcement at the turning iron. When the axial position of reinforcement at both ends cannot be moved, this pull head form can only be used, such as reinforcement butt joint in the connection construction of two prefabricated large-scale concrete structures.

2.2

Technical preparation: the following issues shall be comprehensively considered during reinforcement turnover：

1) The thickness of concrete protective layer of rolled straight thread joint shall meet the requirements of the thickness of protective layer of stressed reinforcement in the current national standard code for design of concrete structures, and shall not be less than 15nmm.

2) The positions of rolled straight thread joints of stressed reinforcement shall be staggered from each other. In the section from the center of any joint to the length of 35 times the diameter of the reinforcement, the percentage of the cross-sectional area of the stressed reinforcement with joint in the total cross-sectional area of the reinforcement shall comply with the following provisions：

a. The percentage of stressed reinforcement joints in the tensile area shall not exceed 50%,

b. The joint should avoid the stirrup densification area at the beam end and column end of the frame with seismic fortification requirements; When unavoidable, the percentage of joints shall not exceed 50%.

c. The percentage of joints in the compression area and the parts where the reinforcement is less stressed in the fabricated members may not be limited.

3) According to the actual situation of the reinforcement to be connected, select the model of the reinforcement connecting sleeve and the direction of the screw thread, and timely adjust the reinforcement cut short due to blanking, processing the screw head and random cutting and sampling inspection.

2.3

Personnel preparation all operators engaged in the processing and connection of equal strength rib stripping and rolling straight thread thread head must undergo strict professional and technical training, pass the examination of the competent department and obtain the corresponding job certificate before they can work. It is strictly prohibited for unlicensed personnel to leave or replace their posts.

2.4

The main machines used for strong rib stripping and straight thread rolling, such as main machines and tools, include grinding wheel cutting machine, straight thread rolling machine, torque wrench, etc.

3. Main construction methods

3.1 process flow: blanking and flattening → rib stripping and thread rolling → thread head inspection → connection with reinforcement connecting sleeve → joint inspection → completion

3.2 Joint construction

1) For cutting and blanking, the reinforcement with non straight ends shall be straightened in advance. According to the requirements of the regulations, the end face of the notch shall be perpendicular to the axis without horseshoe shape or deflection. Therefore, neither blade cutter nor oxygen blowing cutting can meet the requirements of machining accuracy. For the whole length, only grinding wheel cutter can be used to cut one by one according to the length of material.

2) Machining wire head

a. The processing process of wire head is as follows: clamp the steel bar to be processed on the bench clamp of the equipment, start the machine, pull the feeding device, the power head moves forward, start stripping the rib and rolling the thread, after rolling to the set position, the equipment will automatically stop and reverse, pull the end of the steel bar out of the power head, pull the feeding device to reset the equipment, and the processing of the steel bar wire head will be completed.

b. When machining the wire head, water-soluble cutting fluid shall be used. When the temperature is lower than 0 ℃, 15 ~ 20% sodium nitrite shall be added. It is strictly prohibited to use engine oil as cutting fluid or process wire head without cutting fluid.

c. The processing length of the screw head is 1 / 2 of the length of the standard reinforcement connecting sleeve, and its tolerance is + 2p (P is the pitch).

d. The operator shall check the processing quality of the screw head according to the requirements of the following table, and use the go and no go ring gauge to check every 10 screw heads.

Methods and requirements for quality inspection of reinforcement wire head

S / N inspection item measuring tool name inspection requirements

1. The thread profile shall be visually inspected and the caliper profile shall be complete. The cumulative length of incomplete thread with major diameter lower than pitch diameter shall not exceed the circumference of two threads

2. Screw head length caliper and special gauge are 1 / 2 of the length of standard reinforcement connecting sleeve, and the tolerance is 2p (P is pitch)

3. The thread diameter through end thread ring gauge can be screwed into the thread smoothly

e. The qualified screw heads shall be randomly sampled and inspected by the full-time quality inspector of the project department, the unqualified screw heads shall be cut off, the causes shall be found out and solved, and then the threads shall be reprocessed.

f. The qualified screw heads shall be protected, and their ends shall be equipped with protective caps or tightened with reinforcement connecting sleeves, which shall be stacked neatly according to specifications.

3) Field connection processing

a. When connecting the reinforcement, the specification of the reinforcement and the specification of the reinforcement connecting sleeve shall be consistent, and the screw thread of the reinforcement and the reinforcement connecting sleeve shall be clean and intact.

b. When embedded joints are used, the position, specification and quantity of reinforcement connecting sleeves shall meet the design requirements. The reinforcement with reinforcement connecting sleeve shall be fixed firmly, and the exposed end of reinforcement connecting sleeve shall be provided with protective cover.

c. The rolling straight thread joint shall be constructed with pipe wrench and torque wrench, and the two steel wire heads shall be pressed against each other in the middle of the steel bar connecting sleeve. The tightening torque of the joint shall comply with the provisions in table. The accuracy of torque wrench is ± 5%.

d. After tightening, the rolled straight thread joint shall be painted with red paint for identification, and the length of single side external exposed thread buckle shall not exceed 2p.

4. Quality control

4.1 when rolling straight thread joint is applied in the project, the technical cooperation unit shall provide effective type inspection report.

4.2 before and during the reinforcement connection operation, the joint connection process inspection shall be carried out for each batch of mobilized reinforcement, and the process inspection shall meet the following requirements:

4.2.1

There shall be no less than three test pieces of reinforcement connection joints of each specification;

4.2.2

The tensile strength test shall be conducted for the base metal of the reinforcement of the joint test piece；

4.2.3

Tightening torque test and unidirectional tensile strength test shall be carried out for on-site inspection. Pay attention to the visual inspection and acceptance of cutting and blanking and thread processing during construction. Strictly control the process of self inspection, handover inspection and full-time inspection.

4.2.4

Use a torque wrench to spot check the construction quality of the joint according to the specified joint tightening torque value. Sampling inspection quantity: 15% of the number of joints for beam and column components, and the number of joints for each component shall not be less than one joint; For foundation, wall and plate components, every 100 joints are regarded as an acceptance batch, and less than 100 joints are also regarded as an acceptance batch. Three joints are sampled in each batch. All joints sampled for inspection shall be qualified. If one joint is unqualified, the acceptance batch shall be inspected and tightened one by one.

4.2.5

The uniaxial tensile strength test of rolled straight thread joint shall be carried out according to the acceptance batch. Under the same construction conditions, 500 joints of the same grade, type and specification of the same batch of materials shall be inspected and accepted as one acceptance batch, and less than 500 joints shall also be regarded as one acceptance batch.

4.2.6

Each acceptance batch shall be inspected and accepted according to the performance of class a joints in general technical specification for mechanical connection of reinforcement jgj107-96, and three specimens shall be randomly selected from the engineering structure for unidirectional tensile test. When the tensile strength of the three test pieces is not less than the standard value of the tensile strength of the grade of reinforcement and not less than 0.9 times the actual tensile strength of reinforcement equipment, the acceptance batch is determined to be qualified. When calculating the actual tensile strength, the actual cross-sectional area of reinforcement shall be used. If the tensile strength of one test piece fails to meet the requirements, another six test pieces shall be taken for re inspection. If one test piece still fails to meet the requirements, the acceptance batch shall be determined as unqualified. There are three failure modes in the uniaxial tensile test of rolled straight threaded joints: the base metal of the reinforcement is broken, the sleeve is broken, and the reinforcement slips from the sleeve. Any failure mode can be determined as long as the strength requirements are met.

Our company brings its own equipment, materials and personnel to the construction site for construction. The project department does not need to purchase any materials. The project department is responsible for steel bar blanking, material transfer and on-site sleeve installation. All other matters are borne by our company.

B: Advantages of this mode adopted by the project department:

1. Save worry and trouble;

2. Ensure project quality and progress;

3. The quality responsibility is clear, which shall be borne by our company.

C: This mode is applicable to the following practical situations:

1: The reinforcement team members are not skilled in reinforcement straight thread processing technology and have no good construction experience.

2: The number of reinforcement joints is large and the project progress is tight.