ANALYSIS OF DOMESTIC AND WORLD STANDARDS REGARDING THE CRITERIA OF THE BOUNDARY STATES FOR THE STEEL SILOS FOUNDATIONS

Abstract

In the process of operation the structures of steel silos undergo various failures associated with natural and climatic loads and influences, the insufficient study of engineering and geological conditions, as well as some errors during operation. Damage to the above-ground structures of steel silos is mainly caused by roof structures and silo shells failures. Whilst operating silos, various types of raw material flow are distinguished during unloading. Possible scenarios of the operating technology violations can lead to deviations from the approved flow regime during unloading and they quite often become factors of an emergency situation. The conditions of loading and operation of silos have been compared pursuant to their presentation in the domestic and the foreign regulatory documents. A significant number of industrial accidents are associated with operation failures of reinforced concrete foundations, their insufficient load-bearing capacity and their deformability. It should be noted that the construction of the foundation affects its "flexibility", which may cause uneven settlement of the foundations and their base. Sometimes this leads to extra-design loads on the upper structure of the silo. In the domestic practice of increased diameters silos construction, the foundations with an underground gallery are the most common. For the construction areas having a high level of groundwater, the foundations with an above-ground under-silo storey are used. For the silos with an above-ground discharge funnel, the type of outflow influences the load pattern of the foundation. Whilst operating normally, the loads are uniform, and when the storage material hangs on the walls, the loads are uneven, which can lead to the destruction of the above-ground structure or a foundation tilting. The type of funnel significantly determines the shape of the outflow, which affects the distribution of internal forces in the silo and the load on the foundation. In this work, a brief analysis of the failure factors of steel silos has been carried out, and a comparative analysis of modern domestic and international design standards has been suggested concerning the criteria for the occurrence of boundary states of steel silos foundations during designing. There has also been analyzed the special operational features taking into account specific technological loads on silo shells and foundations, the certain features of engineering and geological conditions of construction sites. Conclusions have been made that the main criteria for foundations designing and calculating are the deformation criteria for limiting settlement and tilting. It should be noted that the foreign regulations place the issue of limiting maximum settlements within the scope of a designer's competence. Keywords: reinforced concrete foundation, steel silo, failure, boundary state, design norms.