Research On The Out-of-plane Stability Of Crane Jib With Multi-point Flexible Support

With the rapid development of national economy, crane is being widely usedin the modern production and construction process. There are two develop ingdirections including lightening and enlargement. As for the lightening, mobileconstruction crane, which can be assembled quckily and automatically, turns to bea developing hot point. And for the direction of enlargenment, big-radius towercrane with multi-rod, combined boom system with main jib and fly jib and crawlercrane jib with auxiliary bracing are the hot points of development. All of the aboveboom systems are equiped with string tension systems. Following forces areintroduced by the draw-off of the fexible string, which makes structral analysismore complicated. The stability analysis is frequently implemented to get thenumerical result with fnite element method(FEM). But few researches can befound aboout the analytical method for the buckling of jib at present. Aimed at thisresearch blank, the out-of-plane stability of the beam with multi-point flexiblesupport under draw-off of string tension system is studied in the article. Theanalytic expression of the out-of-plane buckling characteristic equation is deducedto make a few contribution to the development of the related cranes.The out-of-plane stability of jib with single rod and two rods is studied, andthe buckling characteristic equation is obtained. After that, the method is extendedto jib with multi-rod and the recurrence formula is presented. Then, the stabilityanalysis model considering lateral flexibility of fixed joint is built to get thegeneralized buckling characteristic equation. The degeneration forms of thecharacteristic equation under the limit case of zero or infinite lateral stiffness arefurther disscussed. At last, the influence of the lateral stiffness of fixed joint on thestability of jib is investigated.Based on the method of deflection differential equation, boundary conditionsand the deformation compatibility equations are introduced to get the out-of-planebuckling characteristic equation of mobile construction crane jib, which is equipedwith tension strut between two boom segments. Furthermore, the structureparameter including dip angele of the strut, inertia moment of the strut andposition of fixed joint are explored to find out the effect on the stability of jib.After that, lateral stiffness of fixed joint is introduced to get the generalizedbuckling characteristic equation and its effect on the stability of jib is discussed.With use of boundary conditions and the deformation compatibility equations, the out-of-plane buckling characteristic equation of bending beam-column andcombined boom system with main jib and fly jib is obtained using the method ofdeflection differential equation. The angle between two beams is studied and itseffect on the stability of boom system is presented. The result showed that,downwards-bent beam had higher lateral stability than straight beam, but theupwards-bent beam had lower lateral stability. And the draw-off of the stringtension system can improve the stable bearing capacity of boom system. At last,the out-of-plane stability of crawler crane jib with auxiliary bracing is studied.And the buckling characteristic equation is obtained.The out-of-plane stabilities of most common crane jibs with multi-pointflexible support are studied systematically in in the article. Qualitative analysisresults are presented. The work of the article provides theoretical support for theapplication of this kind of crane jib. Also, the work is used as technical reserve forfurther revision of the relative codes for crane structure.