Erection Stability (Overturning) Checker Calculator

Formula Used

Interpretation: a higher SF indicates greater resistance to overturning. The middle-third and no-tension checks help flag uplift risk on the base.

How to Use This Calculator

1. Define the toe as the edge most likely to lift or tip.
2. Enter base width B and effective base length L.
3. Add stabilizing vertical loads and lever arms from the toe.
4. Add lateral loads and their heights above the base.
5. Include any extra direct moments from anchors or braces.
6. Set the required safety factor for the erection condition.
7. Press “Check Overturning Stability” to see results above.
8. Export the CSV or PDF report for your site documentation.

Always validate loads, units, and load paths with project documents.

Example Data Table

These examples are illustrative only. Use project-specific loads for design.

Erection Stability Guidance Article

1) Why overturning checks matter during erection

Erection stages often create short-lived, high-risk configurations. A partially supported member can see large lateral loads with limited stabilizing weight. This calculator quantifies overturning demand and resistance using moments about a chosen toe, helping crews identify when temporary bracing, ballast, or sequencing changes are needed.

2) Typical safety factor targets used on sites

Many teams apply higher safety factors for temporary conditions than for in-service design. A common erection target is 1.5 or greater, while permanent checks can be 2.0 or more depending on the governing standard and risk profile. Use the preset as a starting point, then apply project requirements and engineer approval.

3) Converting loads into overturning moments

Overturning moment is calculated by multiplying each lateral load by its height above the base: Mo = Σ(H·z). Wind on a tall panel, crane side-pull, or accidental impact can be modeled as discrete forces. If a load is distributed, convert it to an equivalent resultant and apply it at the centroid height to keep the check conservative.

4) Building resisting moment from weights and lever arms

Resisting moment comes from vertical stabilizing forces times their lever arms: Mr = Σ(W·a). Self-weight may act near mid-width, counterweights can be placed further from the toe to increase leverage, and temporary stacked materials should only be counted if they are secured and reliably present for the whole lift or set operation.

5) Resultant location, eccentricity, and uplift risk

The resultant location x = (Mr − Mo)/ΣW indicates where the base reaction shifts under combined effects. Eccentricity e = (B/2) − x is used to flag uplift potential. When |e| exceeds B/6, the no-tension assumption breaks and the base may lift at the heel or toe, requiring redesign of temporary works.

6) Bearing pressure checks for base contact stress

Average bearing is qavg = ΣW/(B·L). The calculator estimates qmax and qmin using linear pressure distribution. Negative qmin indicates tension, meaning loss of contact. Compare qmax to allowable bearing for the supporting surface (soil, slab, timber mat) and confirm any mats or grillages spread load adequately.

7) What to do when results show “REVIEW”

Start by validating inputs and units. If overturning dominates, consider lowering lift height, adding temporary braces, increasing counterweight lever arm, or reducing wind exposure through scheduling and shielding. Recheck with the updated configuration and document the chosen controls in the exported report for site verification.

8) Documentation and field practicality

Use the CSV for quick sharing and the PDF for sign-off packages. Record the assumed toe location, load sources, and any temporary measures such as anchors or braces. Practical stability depends on connections, friction, and construction tolerances, so pair these calculations with on-site inspection and a competent person’s review.

FAQs

1) Which edge should I choose as the toe?

The toe is the edge most likely to rotate upward during overturning. Choose the critical edge for the current lift direction, wind direction, or handling condition. Re-run the check if the critical direction changes.

2) What units should I use for inputs?

Use kN for forces, meters for distances, and kN·m for moments. Bearing outputs are in kN/m². Keep all entries consistent; mixing units will produce misleading results even if the math runs correctly.

3) Can I model distributed wind loads?

Yes. Convert distributed pressure to a single resultant force and apply it at the centroid height of the loaded area. If uncertain, bias toward a higher resultant and height to remain conservative.

4) What does a negative qmin mean?

Negative qmin indicates tension in the assumed linear bearing distribution, which usually means partial base uplift or loss of contact. Review the temporary works and consider adding restraint, increasing weight, or widening the base.

5) How do anchors or braces fit into the calculator?

If an anchor or brace provides a known stabilizing moment, enter it as extra resisting moment. If it adds a destabilizing effect, enter it as extra overturning moment. Confirm capacity and connection details separately.

6) Why does the middle-third check matter?

Keeping the resultant within the middle third helps avoid tension at the base. It is a quick indicator of whether contact pressure remains compressive across the base, reducing the risk of rocking and uplift.

7) Is a “PASS” always safe to proceed?

No. “PASS” means the entered loads meet the selected criteria. Field conditions like uneven support, dynamic effects, connection slip, and construction tolerances still matter. Use competent supervision and follow approved erection procedures.