Calculate the Tension Force in Sling
The rigging configuration shown below will be used to lift a bridge girder using a 200-ton capacity luffing jib crane onto the foundation abutment. The tension force (lb.) in Sling A is most nearly:
Solution:
By inspection, the center of gravity of the load is offset causing an eccentric load condition. The reaction load is heavier on the left side (R_{L}). The distribution of the 40,000-lbs load at RL is: (40-ft ÷ 60-ft) (40,000-lbs) = 26,667-lbs. The reaction force R_{L} must be adjusted for the slope of the slings. The vector force length of Sling A is √ 60^{2} + 20^{2} = 63.25-ft. The force in Sling A is (63.25-ft ÷ 60-ft) (26,667-lbs) = 28,111-lbs