How do you determine the strength needed in inserts used for tilt-up panels?
The working stresses change during lifting. At first the insert must resist only the tension produced by the dead load of the panel and strongbacks plus any bond between the panel and the casting face. While suspended it may have to withstand shear impact. An impact allowance of 50 percent is applied to the safe working capacity of the insert for both tension and shear. A panel that weighs 5,000 pounds should be handled with inserts having a safe working load rating of 7,500 pounds in shear and tension.