AN INVESTIGATION OF HOIST-INDUCED DYNAMIC LOADS ON BRIDGE CRANE STRUCTURES

A series of tests were performed on a bridge crane to investigate how the peak dynamic response during hoisting is affected by the stiffness of the crane structure, the inertial properties of the crane structur e, the stiffness of the cable-sling system, the payload mass, and the initial conditions for the hoisting operation. These factors were vari ed in the test program and time histories were obtained for displaceme nts, accelerations, cable tension, bridge bending moment, and end truc k wheel reactions. Values for the dynamic ratio, defined as peak dynam ic value over corresponding static value, are presented for displaceme nts, bridge bending moment, and end truck wheel reactions. A two degre e of freedom analytical model is presented, and theoretical values for the dynamic ratio are calculated as a function of three dimensionless parameters that characterize the crane and payload system. The predic ted dynamic ratios are found to be conservative when compared with the test results. A general format is suggested for dynamic factors in de sign standards that apply to bridge cranes with constant speed motors.