Heavy Civil Exam 1 Practice

In a three-leg sling, the load is shared among the legs, and each leg carries only the vertical component of its tension. As the angle from vertical increases, the tension in each leg must rise to keep the same overall weight supported. Since the load on each leg grows with 1/cos(θ), keeping the angle from vertical limited helps prevent overloading any single leg and keeps the load stable and balanced.

Choosing a limit of 45 degrees keeps the per-leg tension at a reasonable level while maintaining good load distribution among the three legs. If the angle were larger, tensions would increase more quickly and could exceed the sling’s capacity or compromise stability. Hence, the recommended maximum is 45 degrees.