Yermakova S. Substantiation of loads on the support and running equipment of self-propelled jib cranes

The dissertation is devoted to development and perfection of methods of calculation of loadings on basic and running elements of jib self - propelled cranes taking into account conditions of leaning of cars on the ground at their work in difficult operational situations. The analysis of existing methods of calculation of loadings on basic and running elements which are applied to definition of stability of jib cranes is carried out. A method for determining the loads on the supporting and running elements and support planes taking into account the physical and mechanical properties of soils is proposed. Calculation schemes and mathematical models are developed, which take into account the rigidity, inertia and conditions of changing the position of the machine during the deformation of the reference plane, improved methods for calculating the load of the support elements. It is determined that in the process of crane operation in the event of dynamic loads caused by the rigidity of the system, significant fluctuations in the load of the running gear are possible, which leads to redistribution of loads on the supporting elements. Ways to reduce these loads with the help of damping devices have been found. Physical models of jib self-propelled cranes are developed and experimental researches of adequacy of results of mathematical and physical modeling of processes of work of the crane and definition of loading of basic and running elements are carried out. The analysis of the obtained results showed the adequacy of theoretical and experimental studies with an error from 13.6% for the study of dynamic loads to 18% for studies of loads on the supporting elements of a four-support circuit and up to 22% for a multi-support circuit when interacting with soil. Separate experiments were performed on a physical model of a crane with a four-support contour on a rigid surface, which showed uneven load on individual supports and loss of stability of the model when suddenly removing loads from the load-carrying or load-holding body. Based on the comparative analysis of theoretical and experimental loads on the support-running elements, the influence of self-propelled jib crane suspension systems on the value of dynamic loads is shown and the main directions of their reduction are shown by using elastic-damping devices and combined beam-cable system. speakers from 1.5 to 1.25, which will take it into account when determining the stability of the crane.