Structural Analysis And Optimization Design Of Tower Crane Jibs Based On Ansys

Tower crane is a kind of non-continuous handling machinery. It’s widely used to lift prefabricated components and other building materials and tools in industrial and civil construction. The jib is one of the most important load-carrying parts of the tower cranes. Because of its long length and heavy weight, it is also the weakness of strength of the jib structure. Its mechanical properties have a direct impact on the normal operation of the tower cranes which have great harmfulness and can result in higher failure rates. So it is very necessary to reduce the weight (or volume) as much as possible in the condition of meeting the requirement of strength, rigidity and stability. And it is helpful to improve the bearing capacity and global stability.Horizontal crane arm is a kind of biaxial bending beam-columns. Its internal force is mainly produced by its own and lifting weight, wind load, inertial load. But the internal forces on different sections along the arm in the length direction are very different. It will waste much material and be harmful to its carrying capacity if the section sizes are the same. So, the design of variable cross section arm (determining the section sizes-according to the internal force distribution) will reduce its own weight and achieve the requirements at the same time.At present, jib frame was widely designed and calculated with finite element analysis software ANSYS, ALGOR, ABAQUS etc. by scholars at home and abroad. And the optimization designs of tower crane jib have ever been done for three typical operating conditions (maximum amplitude; suspension span; minimum amplitude) by many scholars. But most of them regarded specification of steel, and some regarded the whole section size and hanging position as design variables. The design of setting a suitable height difference between the upper chords of the adjacent arms and regarding it as the design variables to do optimization has never been studied. So it will be studied in this article.Taking the jibs of QTZ4810tower crane as the research object, a set of jibs model with constant cross section is built first, then load it and do analysis. In consideration of its economy, it is impossible to set a sole specification for every jib, so it is necessary to group the jibs according to the results of analysis and set the same specification for the jibs with similar stress. Then optimize the design, in condition of meeting the requirement of strength, rigidity and stability, regarding specification of steels and the height difference between the upper chords as design variables, seeking to minimize the total volume, with the method of first-order for30times. At last, integrating steel specification table, a set of reasonable optimization results is received.In order to ensure safety, a new model with the optimization size is reestablished to reload and analysis. The results show that the model with the optimization size can also meet the requirements, and its volume is about29.29%less than that before optimization, also about23.73%less than that produced at present. On the other hand, five load conditions are considered (two positions where the rods hang besides that three positions mentioned above), so the results can reflect the actual condition better and are more reliably.