According to the "Steel Structure Engineering Construction Quality Acceptance Code", the allowable deviation of the column positioning axis is 1mm. Whether the anchor bolt is buried correctly is an important stage in the steel structure hoisting process, including the installation of the anchor bolt, the measurement of the deviation during the pouring of concrete and after the concrete solidifies.

1) Before installing the anchor bolt, carve the "cross" center line on the steel plate of the anchor bolt;

2) After the steel bar is tied, accurately project the theoretical "cross" center line of the anchor bolt on the steel bar;

3) Use the elevation control network to measure the elevation point near the anchor bolt;

4) Install the anchor bolt using the center line on the steel bar;

5) Set up two theodolites in the direction of the center line of the anchor bolt to accurately direct the installation of the anchor bolt; use the level to direct the adjustment of the height of the anchor bolt;

6) Repeat the above two processes until the plane position and elevation of the anchor bolt meet the requirements of the specification.

Steel column measurement and correction

1. Theodolite correction method

During measurement and correction, two theodolites are respectively set up near the longitudinal and transverse axes of the steel column, but the angle of deviation should not be greater than 15 degrees. The distance from the column is about 1.5 times the length of the column. When correcting, first aim at the control line at the bottom of the column. After the theodolite sighting part is fixed, look up at the control line at the top of the column; if they coincide, it means that the column is vertical in this direction. If they do not coincide, adjustments should be made until the two perpendicular directions meet the requirements. When the first steel column is in place, in addition to correcting the verticality, the elevation of the bottom of the column must be adjusted. The elevation of the first column is adjusted by adjusting the nut at the bottom of the column to ensure the accurate placement of the steel beam.

When correcting the steel column with a cable wind rope, when the cable wind rope is loosened, the column can maintain a "0" displacement state, and the correction can be considered complete. If the cable wind rope has a large force, the column will have a large internal installation force, and the cable wind rope will be loosened. The position of the column will change, which will also cause a large change in the structure, and the correction cannot be considered complete at this time.

2. Spatial resection technology

Due to the limitations of construction site conditions, the following problems may occur during construction work on the working layer: the on-site control points cannot be seen, the instruments cannot be set up on the known points, and the sight is blocked for a long time. To solve the above problems, spatial resection technology is used. The total station is set up in a position with good visibility, and the center coordinates of the instrument are resectioned using the "resection method", and then the coordinate data is used for layout.

Steel beam installation measurement and control

When the steel column calibration is completed, the next process is to hoist the steel beam. Before installing the main beam, the welding deformation value is reserved according to the welding shrinkage, and the reserved deformation value should be recorded in writing. If the verticality of the column is achieved during installation, then when installing and calibrating the steel beam, the column should be propped open to leave the joint welding shrinkage. At this time, the internal force generated by the column will automatically disappear after the welding is completed and shrunk.

The beams and steel columns are connected with high-strength bolts. Since the main beam between the columns has a large cross-section and high rigidity, the verticality of the steel columns will be affected when installing the main beam between the columns. Therefore, the columns need to be further tracked and corrected; the columns of the main beams connected to the spans or even more than two spans should also be monitored together. Only by taking such measures can the installation quality of the columns be guaranteed.

After the high-strength bolts are tightened, the steel columns in this area are observed again as a whole and recorded. According to the deviation value and deviation direction recorded, it is determined whether the deviation before welding needs to be adjusted locally and the welding sequence, welding direction, and the tilt reserve for welding shrinkage are determined, and then delivered to the welding team for welding.

After the high-strength bolts are finally tightened, the next process is welding, and the welding seam will shrink during welding. Therefore, after the welding is completed, the steel columns and steel beams in this area must be re-measured again and recorded. The measurement data recorded after the calibration are sorted out as the pre-control data for the hoisting correction and welding of the next layer of steel columns.

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