The Research On The Dynamic And Static Stiffness Of Luffing Jib Cranes With Great Flexibility

With the common used of high-strength steel, the strength and the workingspeed of Luffing Jib Cranes are enhanced. But its stiffness becomes weaker. Sopeople pay more attention to the analysis by considering the nonlineardisplacement. By considering multiple factors that affect the static and dynamicstiffness of Luffing Jib Cranes with great flexibility, gain the accurate, simple,practical calculation expression of static and dynamic stiffness. And theexpression of their relationship is provided.The solid-web equivalent model of Luffing Jib Cranes is built byconsidering the influences of the web members in the lattice structure. By usingthe non-linear theory, obtain the accurate explicit expression of the lateraldisplacement of flexible Luffing Jib Cranes by taking the dead weight and liftingload into consideration. On the basis, get the effective length and amplificationfactor of deflection, and make the expression easy for the engineering calculation.And come to the conclusion that with the increase of the angle of jib andhorizontal, the lateral displacement and amplification factor of deflectionincrease. Analyze the influences of the dead weight and jib that effect on thestatic stiffness of Luffing Jib Cranes, confirm the importance of dead weight andjib.According to the kinetic energy equivalent principles, single DOF model ofLuffing Jib Cranes is built, and make the calculation easy. Compare withprevious methods, the computational accuracy of the model is improved byconsidering the influences of web members and axial forces. And expression ofthe relationship between the static and dynamic stiffness is built.The result of Luffing Jib Cranes static and dynamic stiffness calculated byexpression given in this paper is the same as the result calculated by usingANSYS in the typical Luffing Jib Cranes calculation analysis. It shows thataccuracy of methods given in this paper is enough for the engineering andscientific research. The methods in this paper can provide a theoretical basis forthe calculation of Luffing Jib Cranes static and dynamic stiffness in the designrules for cranes.