Oksenenko K. Reliability analysis of spiral-fold silos for bulk materials

The thesis is devoted to the development of a methodology of reliability analysis of spiral-flange silos. In the first section, it was analyzed the state of research in the field of the thesis. The metal sheet structures, their features, specifics of operation in different conditions, and calculation features were considered as a research base for the theory of thin-walled silos analysis. The classification of metal silos is formulated and the field of their application was explored. The set of equipment for the construction of the spiral-fold silos was given, the step-by-step process of formation of the folding lock and features of the installation process were presented. The theory of determining the pressure of bulk material on the bottom and walls of silos was considered. A review of works in the field of research about metal silos and reliability studies of building structures was carried out. In the second section, to further accomplish the research task, the history of the invention of spiral-fold structures was gathered and studied. The area of application of spiral- fold silos (foreign and domestic experience) is analyzed. The technical characteristics of the capacities depending on the functional purpose are collected. A table with general data concerning the parameters of spiral-fold silos used in various industries has been developed. The third section considers the design specifics of the spiral-fold silo, which affects to their stress-strain state. A comparison of methods for determining loads and impacts on silo structures according to different regulatory documents was carried out. The features of the design scheme of spiral-flange silos were analyzed. An algorithm of strength design of a metal silo was presented. The stress-strain state of the inter-flange section of the shell with a constant wall thickness is considered. The comparison of the calculations with the finite element calculations in the LIRA-SAPR software package is carried out. In the fourth section, it was described the experimental study of the folded lock on tensile loads. The character of the folded lock and the adjacent areas of the shell under tensile loads was revealed. The bending of the adjacent shell during the opening of the folded lock was recorded. The stages of loading at which the folded lock worked elastically were noted. The revealed character of the folded lock operation before failure basically corresponds to the out-of-limit state of the spiral-fold silo shell, which confirms its reliability under the influence of possible increased failure loads. An experimental study of the operation of the inter-flange zone of the shell and the adjacent folded locks of the spiral-fold silo was carried out. The character of interaction and deformation of the wall with the folded lock was revealed. The degree of folded lock opening under load was estimated. The data concerning the character of the wall and the folded lock in the limit and non-limit states were obtained. The experimental results were compared with the finite element analysis in the LIRA-SAPR software package. The conclusion about the reliable operation of the spiral-fold silo wall under operational and increased loads was substantiated. The fifth section reviews examples of the construction of metal spiral-fold silos in Ukraine. The technical characteristics of the constructed silos and their application areas were considered. The experience of operation of metal spiral-column silos by the example of two elevators was described. The silo elevator of the enterprise LLC Yemilovsky KhPP was considered. The spiral-fold silos of this enterprise are a confirmation of the durability of such structures, which have been in operation since 1971. The silos of the Botievo elevator (Zaporizhzhia region) was inspected. Based on the review, a conclusion was made about the reliability of spiral-fold silos. The operating experience of the Botievo elevator proves that silo discharge and loading systems are important technological processes that affect not only to the productivity of the elevator, but can lead to accidents if the system is not designed and operated properly. Other examples of spiral-fold silo failures were considered and the reasons that caused them were analyzed. In sixth section, it was developed a method of reliability analysis of metal spiral-fold silos based on the analysis of the strength reserve. The reliability analysis was carried out for three states of the silo structure: taking into account ring stresses, taking into account a complex stress state, and a complex stress-strain state. According to the results of the analysis, the parameters of reliability analysis of spiral-fold silos were compared; diagrams of stresses and safety characteristics were plotted depending on the range of bulk material characteristics (wheat). The obtained results of the analysis confirmed the high reliability of metal spiral-fold silos.