Nemchuk O. Residual strength determination of metals structures calculations of harbor cranes working in the excessive operation conditions

The paper solves an important scientific and technical problem in the system of operation of hoisting and transport machines of seaports - determining the residual strength of large metal structures of port cranes in terms of their excessive operation. The solution is to create an effective method of technical diagnosis, development of theory and practice of methods for calculating the residual strength of metal structures. Practice shows that the existing regulations do not provide structural strength of cranes, as they do not take into account the operational degradation of the mechanical characteristics of steels. It is established that the traditional characteristics of strength and ductility change slightly, but the toughness is catastrophic, which is the main reason for the sudden destruction of metal structures. Microfractographic analysis substantiates the reason for the sharp decrease in the resistance to brittle fracture of rolled steel steels - microbundling between the fibers of the structure and elongated non-metallic inclusions in the rolling direction.