FIELD MODAL TESTING AND EVALUATION OF MODIFICATIONS FOR BRIDGE CRANE STRUCTURES DESIGNED FOR SENSITIVE EQUIPMENT.

Large overhead bridge cranes in particular facilities at the Department of Energy (DOE) uranium enrichment plants are required to exhibit severely restricted vibration levels over a limited frequency range to prevent damage to payloads of sensitive equipment. Methodology for the test consisted of taking frequency response function (FRF) data (using two techniques) for the crane components and payload, analyzing the data to characterize the components and identify component problems, assessing probable payload damage versus the rigorous crane performance specification, recommend structural modifications, and verifying the fitness of the modifications. The verification testing demonstrated the success of the crane modifications for maintaining vibration levels within the specification limits by reducing the levels to less than 50 percent of that allowable.