The embedding accuracy of anchor bolts directly determines the installation quality of subsequent steel structure equipment. Deviations frequently occur during construction due to human factors, equipment conditions, environmental changes and technical operations. This article summarizes seven common causes of anchor bolt embedding errors for on-site construction quality control reference.
1. Drawing Design Errors
Inconsistent parameters and dimension markings between embedding construction drawings and steel structure drawings without prior verification and correction will cause misalignment between the embedded anchor bolts and the steel structure installation reference, resulting in systematic positioning deviations.
2. Survey and Setting-out Errors
Survey and setting-out deviation is one of the most common errors during embedding construction, affected by equipment accuracy, operator proficiency, environmental conditions and benchmark stability. Uncalibrated theodolites lead to insufficient measuring precision; thick-tip marking pens cause inaccurate point positioning; substandard level tools used for axis transferring affect horizontal referencing. Strong on-site wind causes plumb bob displacement, while excessive humidity and poor visibility further interfere with setting-out accuracy. In addition, failure to recheck construction benchmarks and drifting reference points will result in overall dimensional deviations.
3. Positioning Line Pulling Errors
During anchor bolt embedding, control points marked on the foundation formwork need to be transferred to the bolt fixing steel formwork. Due to the spacing between the two sets of formworks, unqualified level tools or one-sided wire fixing on benchmark nails will prevent cross reference lines from intersecting vertically, causing bolt positioning offset and embedding errors.
4. Steel Formwork Hole Position Errors
If the hole positions, hole diameters and spacing dimensions of the bolt fixing steel formwork are not fully verified and corrected before construction, inherent machining deviations of the formwork will directly lead to inaccurate embedding positions of anchor bolts.
5. Bolt Verticality Errors
Failure to use qualified level measuring tools, adoption of low-precision instruments, careless construction operation and inadequate on-site supervision will result in uncorrected bolt inclination, causing excessive verticality deviation of embedded anchor bolts.
6. Welding Deformation Errors
Large-scale and multi-group anchor bolts require welding fixation during embedding. High-temperature thermal stress generated during welding easily deforms the steel support and bolt assembly. Without effective anti-deformation measures and timely calibration, the entire bolt group will suffer positional and angular offset, resulting in overall embedding deviation.
7. Formwork Displacement Errors
Unstable and insufficiently reinforced foundation formwork is prone to displacement and deformation under construction disturbance and concrete lateral pressure during bolt adjustment, steel bar binding and concrete pouring. This causes integral offset of the entire embedded bolt group and leads to batch positioning errors.
