1. In the installation process of multi-storey or high-rise steel structure engineering, the elevation deviation of the top of the column is caused by the elevation deviation. Due to the length deviation in the production of steel columns, after the installation of multiple columns, the accumulated error is caused, resulting in the column elevation out of tolerance.
2. Welding shrinkage deformation, column compression deformation, foundation settlement, too large jacking error of column contact surface, inaccurate measuring instruments and other factors are the causes of elevation and perpendicularity out of tolerance.
3. The time of measurement is not uniform, so the data of verticality measurement is not accurate due to the deviation of light.
4. After the column is installed, it is in cantilever state for a long time and lacks reliable temporary fixing measures. In this case, the perpendicularity of the column is easily out of tolerance.
5. Distortion and bending out of tolerance during steel column fabrication, or permanent deformation during transportation and stacking.
