Anchor Bolt Pattern QA
Separate global setting-out shift, pattern rotation and individual bolt distortion before steelwork installation or costly rework.
Anchor bolt acceptance basis
Acceptance note: obtain written tolerances for the actual base plate, holes, bolt diameter, grout, erection method and steelwork package. Best-fit analysis diagnoses the pattern; it does not remove a global setting-out error.
Anchor bolt coordinate schedule
| Pattern / base | Bolt ID | Design E | Design N | Design RL | Measured E | Measured N | Measured RL | Bolt Ø mm | Hole Ø mm | Evidence / note | Action |
|---|
Setting-out and fabrication status
| Pattern / bolt | Raw ΔE | Raw ΔN | Raw horizontal | ΔRL | Best-fit residual E | Best-fit residual N | Residual vector | Worst spacing Δ | Clearance remaining | Status | Action |
|---|
Design and measured bolt positions
Measured error vectors are exaggerated by the selected display factor. Coordinate axes remain north-up; numerical results are not exaggerated.
Actions and verification report
How to verify anchor bolt patterns
- Confirm the controlled design. Verify the grid, base plate orientation, bolt labels, coordinates, levels and drawing/model revision.
- Measure a consistent point. Observe the same geometric point on every bolt and consider bolt lean, thread damage and access.
- Review raw offsets. Raw ΔE/ΔN indicates the actual setting-out error relative to design.
- Review best-fit diagnostics. Centre shift identifies translation; rotation identifies orientation; residuals identify local pattern distortion after rigid alignment.
- Check spacing and clearance. Base-plate fit depends on pairwise spacing, bolt/hole diameters, washers, sleeves and erection tolerances—not coordinates alone.
- Resolve failures before steel arrives. Confirm the survey independently, communicate restrictions and obtain an engineered repair or concession where required.
What is best-fit rotation?
A least-squares rigid 2D rotation aligns the design pattern to measured bolts after removing their centroids. It helps distinguish a rotated but internally consistent cage from individually displaced bolts.
Why show raw and residual offsets?
Raw offsets matter for global installation position. Residual offsets show the internal shape error after translation and rotation are removed. Both affect engineering decisions.
Does positive clearance guarantee base-plate fit?
No. The simplified clearance is hole diameter minus bolt diameter minus twice the raw horizontal offset. Real fit also depends on simultaneous bolt positions, plate rotation, sleeves, bolt lean and fabrication tolerances.
Is coordinate data uploaded?
No. Calculations, drawing and report preparation run locally in the browser.