You are overseeing a tandem lift of a 60-tonne bridge section with two cranes of equal capacity, each rated for 40 tonnes. Both cranes are positioned identical distances from the centroid of the load. Before the lift, the lift supervisor notices that the rigging arrangement on Crane 1 results in a sling angle of 45 degrees, while Crane 2 has a sling angle of 60 degrees. Assuming the load distribution is otherwise balanced, how will the tension in the slings differ between the two cranes, and what is the implication?

Question: You are overseeing a tandem lift of a 60-tonne bridge section with two cranes of equal capacity, each rated for 40 tonnes. Both cranes are positioned identical distances from the centroid of the load. Before the lift, the lift supervisor notices that the rigging arrangement on Crane 1 results in a sling angle of 45 degrees, while Crane 2 has a sling angle of 60 degrees. Assuming the load distribution is otherwise balanced, how will the tension in the slings differ between the two cranes, and what is the implication?

Answer options: ✅ Crane 1 will experience higher sling tension than Crane 2, potentially increasing its load share.

• Crane 2 will experience higher sling tension than Crane 1, potentially increasing its load share.
• Both cranes will experience identical sling tension, as the load is evenly distributed.
• The difference in sling angles will only affect the hook height, not the sling tension.

Correct answer: Crane 1 will experience higher sling tension than Crane 2, potentially increasing its load share.

Explanation: For a given vertical load, a shallower sling angle (closer to horizontal) results in higher tension in the sling. Therefore, Crane 1, with a 45-degree angle, will have higher sling tension than Crane 2, with a 60-degree angle. This higher tension means Crane 1 will be carrying a greater proportion of the load, potentially exceeding its safe working load limits or creating an imbalanced lift. Sling angle directly impacts tension and therefore the load on the crane.