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Advanced Rigging Charts

This page provides specialized rigging charts, complex load calculations, and detailed guidelines for advanced rigging operations. Designed for experienced riggers handling challenging lifting scenarios.

Share of Load Formula

When lifting an object with multiple lifting points, it's critical to understand how the load is distributed. The Share of Load Formula helps riggers calculate precisely how much weight each lifting point will bear.

Share of Load Formula

Key Principle

The share of load on each lifting point is inversely proportional to its distance from the center of gravity.

Formulas

Point 1's Share
Point 1 = (D₂ / (D₁ + D₂)) × Total Load
Point 2's Share
Point 2 = (D₁ / (D₁ + D₂)) × Total Load

Key

  • D₁, D₂: Distances from the center of gravity to each lifting point
  • Total Load: The entire weight of the object being lifted

This formula calculates how load is shared between multiple lifting points. The farther a point is from the center of gravity, the less load it will bear.

L-Shaped Load Visualization

Sling 1Sling 2D₁D₂C.G.12Point 1 SharePoint 2 ShareTotal Load

This diagram shows an L-shaped object lifted by a spreader beam with two vertical slings of different lengths. The share of load at each point is calculated using the distance from the center of gravity.

Point 1: Larger share (further from C.G.)
Point 2: Smaller share (closer to C.G.)

Level Pick Points & Different Sling Angles

When rigging a load with level pick points but using different sling angles, the tension in each sling will vary. This formula helps riggers calculate the exact tension in each sling based on geometry and load weight.

Level Pick Points & Different Sling Angles Formula

Key Principle

When pick points are at different distances from the center of gravity, the sling tensions vary based on the angle and distance of each sling.

Sling Tension Formulas

Sling 1 (Red)
Tension₁ = (Load Weight × D₂ × L₁) / (H × (D₁ + D₂))
Sling 2 (Blue)
Tension₂ = (Load Weight × D₁ × L₂) / (H × (D₁ + D₂))

Key

  • D₁, D₂: Horizontal distances from center of gravity to pick points
  • H: Vertical distance from pick points to the lifting hook
  • L₁, L₂: Lengths of slings (can be calculated using the Pythagorean theorem)

The formulas account for both the horizontal distance of the pick points and the length of the slings. The tension in a sling is directly proportional to both the opposing pick point's distance from center and the sling's length.

Lifting Scenario Visualization

L₁Tension₁L₂Tension₂12C.G.HD₁D₂Load Weight

This diagram shows a lifting scenario with two slings at different angles lifting a level load. The tension in each sling is calculated based on the geometry of the setup and the load weight.

Sling 1: Tension based on formula
Sling 2: Tension based on formula

Different Level Pick Points & Different Sling Angles

When dealing with stepped loads or loads with pick points at different heights, this formula helps calculate the tension in each sling, taking into account both horizontal and vertical positioning.

Different Level Pick Points & Different Sling Angles

Key Principle

When pick points are at different heights and horizontal distances from the center of gravity, the sling tensions are affected by both the horizontal distances and the vertical heights.

Sling Tension Formulas

Sling 1 (Red)
Tension₁ = (Load Weight × D₂ × L₁) / ((D₂ × H₁) + (D₁ × H₂))
Sling 2 (Blue)
Tension₂ = (Load Weight × D₁ × L₂) / ((D₂ × H₁) + (D₁ × H₂))

Key

  • D₁, D₂: Horizontal distances from center of gravity to pick points
  • H₁, H₂: Vertical distances from pick points to the hook
  • L₁, L₂: Lengths of slings (can be calculated using the Pythagorean theorem)

These formulas account for both the horizontal distances and the vertical heights of the pick points. This is critical for stepped loads where pick points are at different levels.

Stepped Load Visualization

L₁31°Tension₁L₂56°Tension₂ 12C.G.H₁H₂D₁D₂Load Weight

This diagram shows a stepped load with pick points at different heights. The tension in each sling is calculated based on both horizontal distances and vertical heights from the hook to the pick points.

Sling 1 (higher point): Tension based on formula
Sling 2 (lower point): Tension based on formula

Advanced Calculation Methods

  • Complex multi-point lifting calculations
  • Center of gravity determination for irregularly shaped loads
  • Tensions in slings at various angles
  • Stress and strain analysis for critical lifts

Technical Standards Reference

  • ASME B30.5: Mobile and Locomotive Cranes
  • ASME B30.10: Hooks - Design criteria and testing standards
  • ISO 4309: Wire rope inspection and discard criteria
  • API RP 2D: Operation and Maintenance of Offshore Cranes

Load Distribution Visualizations

  • Multiple-point lifting arrangements
  • Vector force diagrams for complex rigging setups
  • Stress concentration models for load-bearing components
  • Dynamic load analysis for motion-sensitive lifts

Specialized Equipment Guidelines

  • Tandem lifting operations with multiple cranes
  • Spreader beam design and selection criteria
  • Specialized sling configurations for uneven loads
  • Jackup systems and hydraulic gantries for precision positioning

Coming Next

We're continuing to expand our advanced rigging resources. Check back soon for more detailed content on:

Static vs. Dynamic Loads

Detailed calculations and coefficients for dynamic load factors in various lifting scenarios

Multi-Crane Operations

Coordination protocols and load distribution calculations for tandem and multi-crane lifts

Complex Equalizer Systems

Advanced equalizer beam configurations for distributing loads across multiple attachment points

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Created by Bigfoot Crane