Lift Inputs
Formula Used
- Total lifted load (t) = (Girder + Rigging + Hook + Misc) × Dynamic factor
- Utilization (%) = (Total lifted load ÷ Rated capacity at radius) × 100
- Capacity margin (t) = Rated capacity − Total lifted load
- Sling tension per leg (t) = Total lifted load ÷ (Effective legs × sin(Angle))
- Max outrigger load (t) ≈ (Crane gross + Total lifted load) × 0.60
- Bearing pressure (kPa) = (Max outrigger load × 9.80665) ÷ Pad area
How to Use This Calculator
- Enter the girder weight and add all below-the-hook items as rigging, hook, and accessories.
- Select a dynamic factor based on lift control, travel, and site conditions.
- Measure the working radius at the final set point, then pull the rated capacity from the correct chart.
- Input expected wind and your project wind limit; stop if wind exceeds limits.
- Enter sling legs and angle to estimate leg tension; match to certified WLL with safety factors.
- If needed, add crane gross weight, pad area, and soil bearing to screen ground support adequacy.
- Calculate, review the status, then export CSV or PDF for lift plan review.
Example Data Table
| Scenario | Girder (t) | Rigging (t) | Dynamic | Radius (m) | Rated (t) | Total (t) | Utilization (%) | Wind (m/s) |
|---|---|---|---|---|---|---|---|---|
| Typical pick | 28.5 | 1.2 | 1.10 | 18 | 55 | 34.21 | 62.2 | 6.5 |
| Tight margin | 40.0 | 1.6 | 1.15 | 22 | 50 | 49.68 | 99.4 | 8.0 |
| Over limit | 42.0 | 2.0 | 1.20 | 24 | 48 | 54.00 | 112.5 | 7.0 |
Professional Notes for Girder Lift Planning
1) Purpose of a Lift Plan
A lift plan links engineering intent to field execution. It records the picked load, configuration, radius, wind triggers, and ground assumptions so the team can verify readiness before each pick and after any change. Document assumptions and approvals so the same plan is followed consistently onsite.
2) Building the Picked Load
Total lifted load includes the girder, rigging, hook block, and accessories. Below-the-hook items often add several percent to the girder. Apply a dynamic factor (typically 1.05–1.20) for start/stop, rotation, and minor travel.
3) Radius Is the Main Driver
Capacity is strongly radius dependent. Small radius increases can reduce chart rating, especially near chart transitions. Measure radius at the final set point and re-check after repositioning, settlement, or boom angle changes.
4) Utilization and Decision Limits
Utilization compares total lifted load to the chart rating at radius. Many teams use bands such as <75% preferred, 75–85% reviewed, and >85% senior sign-off. Lower margin means less tolerance for wind, swing, and corrections.
5) Sling Angle and Tension
Sling tension rises quickly as sling angle decreases. The calculator estimates tension using sin(angle) and conservative effective legs. Match the tension to certified WLL, then verify shackles and connection points using the lowest-rated component.
6) Wind and Load Profile
Wind limits must reflect the crane manual and load geometry. Deep girders and bracing can act as a sail, increasing side load and boom deflection. If gusts approach limits, land the load and reassess before continuing.
7) Ground Support Screening
Outrigger pressure depends on reactions, mat area, and soil strength. This tool provides a conservative screening estimate and converts load to kPa. Use it to flag risk and confirm with engineered mats or manufacturer reaction data.
8) Execution Controls and Records
Controls include exclusion zones, clear communications, taglines, and certified rigging. Export results to CSV or PDF for review sign-offs. Update the record whenever radius, configuration, rigging, or weather assumptions change.
FAQs
1) What should I use for the dynamic factor?
Use 1.05 for smooth, controlled picks with minimal movement. Use 1.10–1.20 for rotation, minor travel, or variable ground. If your method statement specifies a factor, follow it.
2) Where do I get the rated capacity value?
Use the manufacturer load chart for the exact configuration: boom length, counterweight, outrigger setting, and any attachments. Select the value at the measured working radius and the correct parts of line.
3) Why does the calculator use “effective legs” for 4-leg slings?
In practice, one leg can be slack due to geometry or unequal adjustment. Conservative planning assumes three legs share the load. This helps avoid overestimating capacity when selecting rigging hardware.
4) How accurate is the ground pressure check?
It is a screening estimate. Actual outrigger reactions depend on crane geometry, boom angle, and chart notes. Use this result to flag risk and confirm with engineered matting or manufacturer reaction data.
5) What wind limit should I set?
Set the lower of the crane manual limit and the project limit for the load shape. Include gust policy and stop criteria. When wind is variable, adopt a conservative trigger and monitor continuously.
6) How do I reduce utilization if it is too high?
Reduce radius, increase crane capacity, adjust boom length/configuration, reduce rigging weight, or split the lift. Do not proceed above chart capacity. Seek engineering review for any plan change.
7) Can I use this for tandem lifts?
This tool is intended for single-crane planning. Tandem lifts require load sharing analysis, synchronized motions, and dedicated engineering oversight. Use a project-approved tandem-lift procedure and manufacturer guidance.
Professional Notes for Girder Lift Planning
1) Purpose of a Lift Plan
A lift plan ties engineering intent to field execution. It captures the picked load, configuration, radius, wind triggers, and ground assumptions so the crew can verify readiness before each pick and when conditions change.
2) Building the Picked Load
Total lifted load should include the girder, rigging, hook block, and accessories. Below-the-hook items commonly add several percent to the girder. Apply a dynamic factor (often 1.05–1.20) to cover start/stop, rotation, and minor travel.
3) Radius Is the Main Driver
Capacity is highly radius dependent. A small increase in working radius can reduce rated capacity materially, especially near chart transitions. Measure radius at the final set point and re-check after repositioning, ground settlement, or boom angle changes.
4) Utilization and Decision Limits
Utilization compares total lifted load to the chart rating at the selected radius. Many teams adopt governance bands such as <75% preferred, 75–85% reviewed, and >85% senior sign-off. Low margin reduces tolerance for wind, swing, and corrections.
5) Sling Angle and Tension
Sling tension rises quickly as the sling angle decreases. The calculator estimates tension using sin(angle) and conservative effective legs. Match the resulting tension to certified WLL, then confirm shackles and connection points using the lowest-rated component in the path.
6) Wind and Load Profile
Wind limits must reflect the crane manual and the load geometry. Deep girders, bracing, and formwork can act as a sail, increasing side load and boom deflection. If gusts approach limits, land the load, stabilize, and reassess before continuing.
7) Ground Support Screening
Outrigger pressure depends on reactions, mat area, and soil strength. This tool provides a conservative screening estimate for the most-loaded outrigger and converts load to kPa. Use it to flag risk and confirm with engineered mats or manufacturer reaction data.
8) Execution Controls and Records
Controls typically include exclusion zones, clear communications, taglines, certified rigging, and a stop-work checklist. Export the results to CSV or PDF for review sign-offs. Record revisions whenever radius, configuration, rigging, or weather assumptions change.
FAQs
1) What dynamic factor should I use?
Use 1.05 for smooth, well-controlled picks. Use 1.10–1.20 for rotation, minor travel, or uneven ground. Follow your method statement if it prescribes a specific factor.
2) Where does rated capacity come from?
Take it from the manufacturer chart for the exact configuration: boom length, counterweight, outrigger setting, and attachments. Select the value at the measured working radius and correct chart notes.
3) Why is a 4-leg sling treated as three effective legs?
One leg can go slack due to geometry or unequal adjustment. Using three effective legs is a conservative approach that helps prevent overestimating rigging capacity.
4) Is the ground pressure result final?
No. It is a screening estimate. Actual outrigger reactions depend on crane geometry and the lift chart notes. Use engineered matting or manufacturer reaction data for final confirmation.
5) How should I set the wind limit?
Use the lower of the crane manual limit and the project limit for the load shape. Include gust rules and a clear stop trigger. Monitor wind continuously during picks.
6) What if utilization is too high?
Reduce radius, change configuration, upgrade crane size, reduce rigging weight, or split the lift. Do not proceed beyond chart capacity. Escalate for engineering review.
7) Can this be used for tandem lifts?
This tool is intended for single-crane planning. Tandem lifts require load sharing analysis and dedicated procedures. Use a project-approved tandem lift plan and manufacturer guidance.