(I) Construction process
1, steel production
　　 When the steel bar is processed, it is necessary to review the steel bar processing table and design drawing, check whether there are any mistakes or omissions in the blank bar table, and check whether the requirements of each steel bar are determined by pressing the material table. After these two inspections, press the material again. The table will be released in real-life samples, and batch production will be conducted after the trial production is completed. The processed steel bars shall be stacked and orderly and orderly.
　　 If there is a need to replace the steel bars in construction, we must fully understand the design intent and the performance of the replacement materials, strictly abide by the various provisions of the current reinforced concrete design specifications, and do not substitute low-strength steel bars with high-strength steel bars of equal area. Any replacement of steel bars in important parts must be agreed upon by Party A and the design agency, and can be substituted if there is a written notice.
(1) The surface of the steel bar should be clean, and the sticky oil, soil and floating rust must be cleaned before use. The rust can be combined with the cold drawing process.
(2) Straightening of steel bars can be straightened by mechanical or artificial means. The rebars after straightening shall not have local bending, dead bending, or small undulations, and their surface flaws shall not reduce the cross-section of the bars by 5%.
(3) The steel bar shall be cut according to the number, diameter, length and quantity of steel bar, and the short material shall be broken after the long material is cut first, and the short steel bar shall be minimized and shortened so as to save the steel.
(4) Rebar hooks or bends:
1 steel hook. There are three forms, namely semicircular hooks, straight hooks and oblique hooks. After the steel bar is bent, the endothelium of the bend, the extension of the outer skin, and the length of the axis remain the same, and the arc forms a circular arc. After bending, the dimension is not larger than the blanking size, and the bending adjustment value should be considered. The rebar bending center diameter is 2.5d and the straight section is 3d. The theoretical calculation of the length of the reinforcing bar's hooks is 6.25d for semicircular hooks, 3.5d for straight hooks, and 4.9d for diagonal hooks.
2 bend rebar. The bend diameter D at the bend in the middle is not less than 5 times the diameter of the bar.
3 stirrups. The ends of the stirrups should be hooked, and the hooks should conform to the design requirements. The stirrup adjustment is the difference or addition of the length of the hook and the value of the bending adjustment, depending on the size of the stirrup or the size of the inner package.
4 The length of reinforcing steel blanking should be taken into consideration based on the dimensions of the components, the thickness of the concrete protective layer, the bending adjustment value of the steel bar and the length of the curved hook.
a. Straight stock length = member length - thickness of protective layer + length of hook
b. Curved reinforcement blank length = straight length + oblique length - bend adjustment value + hook length increase
c. Stirrup stock length = stirrup inner perimeter + stirrup adjustment value + hook length
2. Rebar tying and installation:
Reinforce the drawings carefully before rebar tying, check whether there is any difference between the ingredient list and the drawings and design, and carefully check the finished product size and whether the heart is consistent with the blanking sheet. After the check is correct, it can be tied.
Use 20# iron wire to tie 12 or more steel rebars and 22# iron wire to tie 10 or less steel bars.
(1) Wall
A wall of steel mesh tied with the foundation. When the steel bar has a 90° hook, the hook should face the concrete.
(2) When double-layer steel mesh is used, between two layers of steel bars, support irons (hooks) shall be provided to fix the spacing of the reinforcing bars.
3 When the ribs are tied, the verticality should be controlled by the wire, and the spacing between the main ribs should be strictly controlled. The three levels on both sides of the shear wall should be tied and the rest can be plumbed.
4 In order to ensure the correct rebar position, a horizontal rib or stirrup is tied to the vertical force ribs and spot welded to the vertical ribs to fix the position of the wall and column ribs. Use a line hammer to correct the spot welding. .
5 It is forbidden to open the hole after the external wall is poured. All openings and buried pipes should be reserved. See the construction drawing for details of the hole reinforcement. Retaining steel bars in the walls and columns shall be used as lightning protection grounding leads and shall be welded into the vias. Refer to the installation and construction drawings for the location, quantity, and methods. Welding work should be performed by qualified welders. Structural reinforcements must not be damaged. Pre-buried hydropower installations must be used in conjunction with civil works and must not be buried or missed.
(2) Beams and plates
1 When double-layered or multi-layered reinforcing bars are arranged in longitudinal reinforcement, short steel bars with a diameter of 15 mm should be placed between two rows of steel bars. If the diameter of longitudinal bars is greater than 25 mm, the specifications of short steel bar diameters are the same as those of longitudinal bars.
2 stirrup joints should be staggered set, and tied with two erection tendons, cantilevered beam is the stirrup joints in the next, the rest with the same column. The outer corners of the beams and the stirrups should be fully barbed, and the rest can be plumbed.
The reinforcement of the 3 steel plates is the same as the foundation, and the cross points of the two-way plates should be fully tied. Should pay attention to the Ministry of the negative reinforcement (surface reinforcement) to prevent being stepped on; in particular, canopies, provocative, balcony and other cantilever boards, we must strictly control the position and height of negative reinforcement.
At the intersection of the 4th plate, the secondary beam and the main beam, the steel plate is on the top, the secondary beams are on the middle layer, and the main beams are under the steel bars. When there are ring beams or cushion beams, the main beams are on the top.
5 The bending starting point of the floor slab reinforcement, such as the processing plant (field) in the process without bending, the design drawings without special instructions, can be bent according to the following provisions of the steel, the board's side span support spans 1/10L for the bend starting point. The mid-span and continuous multi-span of the board can be bent starting point by 1/6L of the centerline of the bearing. (L-plate middle-span).
6 When the reinforcement of the frame beam joints is densely interspersed, the net spacing between the main reinforcements on the top surface of the beam must be kept at 30 mm to facilitate the need for concrete filling.
7 The lashing joints of steel bars should meet the following requirements:
1) The end of the lap length should be no less than 10 times the diameter of the steel bar at the bending point of the steel bar. The joint should not be located at the maximum bending moment of the component.
2) In the tension zone, the end of the Class I steel banding joint should be done
Hooks, grade II rebars do not make hooks.
3) Reinforcing steel joints should be fastened with wire at the center and both ends.
4) The lap length of the tensioned reinforcement tie joints shall comply with the structural design requirements.
5) The thickness of the protective layer of reinforced concrete shall comply with the structural design requirements.
6) Before the ribs are tied, they must be spaced according to the requirements of the design drawings, and tie them according to the line to control the quality.
3, reinforcement length:
　　 According to the design requirements, the rebar with diameter ≥ 18 of this project is preferred to adopt mechanical extension, sleeve extrusion connection technology, and the rest of the reinforcements should be long. Horizontal bars should be butt welding and arc welding. Vertical bars should be electroslag pressure welding. Larger than Φ25 vertical reinforcement using sleeve extrusion connection.
(1) Butt welding operation requirements:
　　 The weldability of Type II and Grade III rebars is good, and the adaptability of the welding parameters is wide. As long as the quality of the welds is ensured, the fracture in the heat-affected zone is small when pulling and bending. Therefore, the key to its operation is to master the right forging.
When using preheat flash welding, the operating points are: a flash, flashing prevail; full warm-up, high frequency; secondary flash, short, steady, strong; upsetting process, fast and powerful.
(2) Arc welding:
Reinforced arc welding sub-welding, lap welding, groove welding and melting tank four joint forms.
1 gang welding: The gang welding is applicable to the connection of the I and II steel bars. The gang bars should be made of the same level as the main bars and the steel bars with the same diameter.
2 lap welding: lap welding is only applicable to the welding of type I, II and III steel bars. The main points of production are not only the pre-bending and installation of overlapping parts of the steel bars, but also the positions where the two steel bar axes coincide with each other. The welding process is basically the same. General single-sided lap welding is 10d, double-sided welding is 5d.
3 Butt welding butt joint subsection groove welding and groove vertical welding butt.
(3) Vertical reinforcement electroslag pressure welding:
　　 Electroslag pressure welding is the use of electric current through the resistance of the slag pool to heat the end of the rebar, and then apply pressure to the steel welding.
Electroslag pressure welding application welding procedure:
Installation of welded steel bar → Installation of arc-striking wire ball → Wound asbestos rope with flux box → Place the flux on the power supply. "Slag making" working voltage 40~50V, "electroslag" working voltage 20~25V → forming slag pool during slagging → electroslag process rebar face melting → cut off power supply top pressing steel to complete welding → unloading flux disassembly welding box → dismantling Fixtures.
1 When welding steel bars, use the welding clamps to clamp the steel bars to be welded up and down respectively. When the upper and lower bars are installed, the center line must be the same.
2 Place the arc-initiated wire ball: Lift up the steel bar, place the pre-prepared wire ball in the middle position of the welding end face of the upper and lower reinforcing bars, put down the steel bar, and lightly press the wire ball to make the contact well. When laying down the rebar, it is necessary to prevent the wire ball from being flattened.
3 Install the flux box: First assemble the asbestos rope at the bottom of the installation flux box, then install the flux box and fill the flux box with flux. When installing the flux box, the welding port should be located in the middle of the flux box, and the asbestos rope should be tightly wound to prevent flux leakage.
　 Press the beginning, turn on the power, lift the steel bar up slightly while turning on the power, ignite the arc, and perform the “lagging delay reading†to calculate the slagging power-on time.
4 Turn on the power and start the arc slagging: The working voltage of the “slagging process†is controlled between 40~50V, and the slagging power-on time accounts for 3/4 of the energization time required for the entire welding process.
5 "Electro-slag process": With the completion of the slagging process, the "Electrolyte Delay Reading" is performed at the same time as the "Electro-slag process", the ESR power-on time is calculated, and the upper rebar is reduced, and the end of the upper rebar is calculated. Inserted into the slag pool, slowly send it to the steel bar until the "electroslag process" is over.
　　 The “electroslag process†operating voltage is controlled between 20V and 25V, and the electroslag electrification time accounts for about 1/4 of the energization time required for the entire welding process.
6 Pressing the steel bar to complete the welding: The “electroslag process†is delayed and the electroslag process is finished. The power supply is cut off, and the steel bar is pressed immediately to form a welded joint.
7 Discharge the flux, remove the flux box, asbestos rope and clamp.
　　 When unloading the flux, the hopper should be stuck under the agent box. The recovered flux should be free of slag and debris. The damp solder should be baked, baked, and reused.
8 After the welding of the reinforcing bar is completed, the appearance of the welded joint shall be checked in time. If the appearance of the joint is not qualified, the rewelding shall be removed.
7) In order to ensure the correct position of the rebar, according to the design requirements, the plate ribs shall be supported with a steel bar vertical and horizontal support @600.
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