Reinforcement engineering construction technology 1. Reinforcement bar lofting Before steel bar processing, technical personnel will loft out each specification of steel bars for various components and fill out the "Reinforcement Bar Ingredients" based on the structural construction drawings, specification requirements, construction plans and relevant negotiations. The specification, shape, length, quantity, application location, etc. of the steel bars are indicated in the "Reinforcing Bar Ingredients List". After the "Steel Bar Ingredients List" has been reviewed and signed by the person in charge of the project technical department, processing will begin. 2. Steel bar blanking Before steel bar processing, the ingredients list must be prepared by professionals and set out. After passing the test and processing, batch processing can be carried out. 1. Rebar hooks or bends 1.1 There are three types of steel bar hooks, namely semi-circular hooks, straight hooks, and oblique hooks. After the steel bar is bent, the inner skin of the bending area shrinks, the outer skin extends, and the axis length remains unchanged. The bending area forms an arc, and the size after bending is larger than the blank size. When calculating the actual ingredients, please refer to the table below to increase the length of the semicircular hook. Reference table for increasing the length of semi-circular hooks (bending with machinery) Diameter of steel bar (mm) <68～1012～1820～28 Length of one hook (mm) 4d6d5.5d5d1.2 The bending diameter D at the bend in the middle of the bent steel bar, Not less than 5 times the diameter of the steel bar. 1.3 The ends of the stirrups should be hooked, and the form of the hooks should meet the design requirements. When there are no specific requirements in the design, the bending diameter of the stirrup hook should be greater than the diameter of the stressed steel bar and not less than 2.5 times the diameter of the stirrup. The adjustment value of the stirrup is shown in the table, which is the added length of the hook and the bending adjustment value. The difference or sum of the items is determined according to the stirrup volume outer size or inner skin size. Stirrup length method Stirrup diameter (mm) 4 ~ 56810 ~ 12 quantity Outer skin size 40506070 quantity Inner skin size 80100120150 ~ 1701.4 The end of the Grade I steel bar needs to be a 180° hook, and the arc curve diameter is not less than 2.5 times the diameter of the steel bar. The length of the straight part should not be less than 3 times the diameter of the steel bar; when the end of the Grade II steel bar must be bent at 90° or 135°, the bending diameter should not be less than 4 times the diameter of the steel bar. The length of the straight part should be determined according to the design requirements. The end of the stirrup should be a 135° hook, and the straight length of the hook end should be 10 times the diameter of the steel bar and the maximum value of 75mm. 2. The cutting length of steel bars should be comprehensively considered based on the component size, concrete protective layer thickness, steel bar bending adjustment value and hook increase length. a. Cutting length of straight steel bars = length of member – thickness of protective layer + increased hook length b. Cutting length of bent steel bars = length of straight section + oblique bend length – bending adjustment value + increased hook length c. Cutting of stirrups Length = inner circumference of stirrup + stirrup adjustment value + additional length of hook 3. For steel bar welding, refer to the relevant provisions of the welding engineering content in this section. 3. Steel bar processing 1. The surface of the steel bar should be clean. Adhering oil, dirt, and floating rust must be cleaned before use. You can use an iron brush or combine with the cold drawing process to remove rust. 2. Steel bars can be straightened mechanically or manually. The straightened steel bars shall not have local bends, dead bends, or small waves, and surface scars shall not reduce the cross-section of the steel bars by 5%. 3. The cold drawing rate of steel bars straightened by cold drawing method: the cold drawing rate of grade I steel bars should not be greater than 4%, and the cold drawing rate of grade II and III steel bars should not be greater than 1%. The lifting rings of prefabricated components must not be cold drawn and can only be used Made of grade I hot-rolled steel bars. 4. The cutting of steel bars should be based on the type, diameter, length and quantity of the steel bars, and the length should be matched. The long materials should be cut off first and then the short materials, and the short ends of the steel bars should be reduced and shortened as much as possible to save steel. 5. The processing and fabrication of steel bars is completed in the processing yard within the site area, and is lifted to the construction department with a tower crane and tied in place. The shape and size of steel bars must comply with the design requirements of the drawings. 6. The shape and size of the steel bar processing must comply with the design requirements of the drawings. The allowable deviations of the steel bar processing meet the following regulations: Project allowable deviation (mm) Net size of the full length of the stressed steel bar along the length direction 10 Bending position of the bent steel bar 20 4. Reinforcement joint form The location of the rebar joints and the number of the same section are set according to the requirements of the design and atlas 03G101. The connection of steel bars in different parts and specifications adopts the following form: ⑴ The steel bars with a diameter of ≥14 in walls and columns are electroslag pressure welded, and the steel bars with a diameter of ≤12 are bound; ⑵ The steel bars with diameters of 22 and 25 in beams are connected by straight threaded sleeves, and the steel bars with a diameter of 20 The following steel bars are welded on one side. ⑶ The steel bars with plate diameter ≥20 shall be connected with straight threaded sleeves, the steel bars with diameter 16 and 18 shall be single-sided welded, and the steel bars with diameter ≤14 shall be bound. 1. Steel bar lashing joints ⑴ The overlap length and joint position of the steel bar lashing joints must comply with the seismic code requirements. ⑵ The distance between the end of the overlap length of the steel bar and the bending point of the steel bar shall not be less than 10 times the diameter of the steel bar. The joint should not be located at the maximum bending moment of the component. ⑶ In the tension area, the ends of the binding joints of Grade I steel bars must be hooked, but the ends of Grade II steel bars and Grade III steel bars do not need to be hooked. ⑷ The ends of compression Grade I steel bars with a diameter of not more than 12 mm, and in axial compression members The ends of stress-bearing steel bars of any diameter do not need to be hooked, but the overlap length shall not be less than 35 times the diameter of the steel bar. ⑸ The overlap of steel bars must be tied firmly with iron wire at the center and both ends. ⑹ The positions of the binding joints between the stress-bearing steel bars must be staggered from each other. Within the range from the center of any binding joint to 1.3 times the overlap length L1, the percentage of the cross-sectional area of ??the stressed steel bars with the binding joints to the total cross-sectional area of ??the stressed steel bars must comply with the following regulations: the tension area shall not exceed 25%; The pressure area shall not exceed 50%.
Steel bar tying 1. Basement floor steel bar tying 1.1 Process flow: Clean the cushion layer → Bind the basic steel bars → Draw or stretch the lines → Bind the stressed steel bars on the lower floor of the floor → Reserve and embed → Set the support of the board and the iron length @ 1500mm → Installation of the waterstop at the post-casting zone → Binding of the upper steel bars of the slab → Enter the next process 1.2 Operation process: ⑴ Before tying, the line should be drawn along the axis direction and equal dividing lines should be drawn on the cushion layer ⑵ Reinforcement grid Binding: The intersection points of steel bars should be tied firmly at each point to ensure that the stressed steel bars do not shift. When tying, attention should be paid to the tying threads at adjacent ligating points to be buckled into a figure-eight shape to prevent the mesh from skewing and deforming. ⑶ The position of the lap joint of the bottom plate steel bar. The bottom bar joint should be set within 1/3 of the span from the support, and the reinforcement should be located outside 1/3 of the span from the support. The joint positions should be staggered according to the design requirements; the position of the welded connection joint should be under the base plate. The skin steel bars are connected within 1/4 of the clear span on the left and right sides of the mid-span or close to the mid-span, and the skin steel bars on the base plate are connected within 1/4 of the clear span of the support or close to the support. Located in the same section (the length of the joint section is 35d and not less than 500), the joint rate of steel bars should not be greater than 50%. ⑷ It is required that the long steel bars of the raft foundation should be connected with straight threads and the short steel bars should be connected with flash butt welding. 2. Wall and column steel bar binding 2.1 Leading out the plane position of walls and columns: There is a 200×200 observation hole on the first floor, and a vertical alignment laser theodolite is erected on the upper floor to introduce the main axis datum point of the lower floor into the building. On the surface, determine the positioning point of the main axis of the floor, measure the position of the main axis with a 50m steel tape, and use an ink fountain to pop out the ink lines on columns, walls, elevator shafts, etc. Deviations in the steel bars must be corrected and accepted before the steel bars are allowed to be tied. 2.2 Binding of column and wall steel bars ⑴ When tying, they must be fully tied. In order to prevent the steel bars from shifting, the protective layer is arranged in a plum blossom pattern with a spacing of 500mm between plastic spacers. After the binding molding is inspected and passed, three stirrups will be tied to the upper, middle and lower parts of each frame and welded to the main bars to enhance the integrity of the frame. ⑵ The overlapping hooks of the column stirrups should be staggered on the four-corner longitudinal steel bars. The stirrups and column bars should be tied firmly with iron wires, and the verticality and spacing of the column bars should be controlled. The vertical reinforcing bars of the basement columns are bent at 90° and tightly bound to the bottom plate steel mesh. The anchorage length of the wall reinforcement is LaE, and the internal and external rows of steel bars in the wall reinforcement are in accordance with the design requirements. Bind ∽-shaped tie bars and arrange them in a plum blossom shape according to the design requirements. The internal tie bars of concealed columns should comply with the design drawings. Additional steel bars will be added to the holes left in the wall according to the node diagram. 3. Binding of steel bars for beams and slabs ⑴ When tying construction, the main beam bars should be tied first, then the secondary beam bars, and then the bottom layer bars of the board. After the bottom layer bars are tied, the mechanical and electrical installation should be laid out and pre-buried, and finally the board should be tied. The upper reinforcements and slab negative bending moment reinforcements will be paved with stone cushion blocks after everything is in place. Where the slab, secondary beam and main beam intersect, the plate reinforcement is on top, the secondary beam reinforcement is in the middle, and the main beam reinforcement is on the bottom. The double-layer steel bars at the bottom of the beam are separated by Φ25 short steel bars with a spacing of 300mm; the double-layer steel bars at the top of the beam are tied with "suspenders". The stirrups at the beam end should be densely packed, and the overlapping hooks should be placed on both sides of the upper opening of the beam and tied in a staggered manner. ⑵ The formwork at the bottom of the beam is installed firmly. After the steel bars of the main and secondary beams are installed and tied, the formwork on both sides of the main and secondary beams is sealed and corrected and reinforced. ⑶ The upper steel bar of the secondary beam rests on the main beam steel bar, and the lower steel bar extends into the main beam steel bar to reach the anchoring length. The short-span steel bars of the two-way slab are in the lower row, and the long-span steel bars are in the upper row. The lower steel bars of the beam are connected within 1/3 of the span from the support, and the upper steel bars are connected within 1/3 of the mid-span. The upper steel bars of the floor anti-beam are connected within 1/3 of the span from the support, and the lower steel bars are connected within 1/3 of the mid-span. ⑷ The floor slab steel bars will be installed after the primary and secondary beam bars are installed and tied. Before laying the steel bars, use chalk to draw the spacing lines between the main bars and the distribution bars on the template, place the stress-bearing bars according to the lines, and then place the distribution bars. The stress-bearing tendons should be placed in the short span direction. In addition to all the intersection points of the two outer steel bars of the one-way plate bars being tied, the intersection points in the middle can be tied at intervals, but all the intersection points of the two-way plate bars are tied. ⑸ Method of supporting steel bars on the upper floor: plastic horse stools are used for steel bar support. The lower row of steel bars of the upper layer of steel bars are placed directly on the plastic horse stools. The horse stool is supported between the double-layer steel bars of the basement floor by using the short span of the upper row of steel bars on the floor as the upper row of steel bars. The horizontal support of the horse stool was changed to the lower row of steel bars, and 22 steel bars were processed into horse stool support pads, which were arranged every 1 meter along the length (as shown below). ⑹ When pouring concrete, especially when pouring slabs and beams, it is difficult to ensure the correct position of the column reinforcements. Therefore, the following methods are used to fix them: before pouring concrete, project the axis onto the formwork, find the position of the column reinforcements according to the axis, and position the columns. All the bars on the beams are welded firmly, and the stirrups and beam steel bars are welded tightly so that all columns, beams, and plate steel bars are welded together into a whole. And during the concrete pouring, a line was taken to check the deviation of the steel bars in time. ⑺ Before the secondary construction (after the first concrete pouring), the vertical bars should be cleaned and trimmed before the steel bars for the secondary construction can be tied. 4. Steel bar overlap, anchorage length, minimum anchorage length of longitudinal tension steel bars (la) and minimum seismic anchorage length (laE) Concrete strength grade steel bar type C20C25C30LaLaELaLaELaLaE plain steel bar, i.e. grade I steel bar = 31d33d27d28d24d25d ribbed steel bar grade II steel bar d≤2539d41d34d35d30d31d Ⅲ Grade steel d ≤ 2546d49d40d42d36d37d Note: ① La The minimum anchorage length of the tensile steel bars of components combined without considering seismic action, this project refers to secondary beams and floor slabs. ② LaE is the minimum anchoring length of tension steel bars for components that consider seismic action combinations. This project refers to frame beams, columns, walls and basement floors.
③ The length of the longitudinal tensile steel bar binding overlap is 1.2 times the anchoring length (when the lap joints of the same section account for 25%)