Measurement of residual deviations of the ship’s hull axis from the initial positio

The article discusses a method for measuring deviations of the deformed axis of a ship’s hull form the initial (non deformed) position that arise with a general residual bend or deflection. The Rules of the Russian Classification Society (RCS) and the Rules of the Russian Maritime Register of Shipping (RMRS) do not have standards for assessing the main characteristics of such deformations (the maximum bend of deflection arrow). Nevertheless, this defect has a significant impact on the overall strength and reliability of the ship’s hull in operation and can cause sudden failure. The presence of general residual deformations of the hull not only negatively affects the strength and reliability of the hull, but also complicated cargo operations and leads to errors in determining the amount of cargo in the tanks of tankers. The result of the research presented in this article is a new technique for measuring deviations of the hull axis of a ship with general residual deformations from its initial nondeformed state, mathematical dependencies for calculating the exact coordinates of the deformed hull axis. This will make it possible to more accurately assess the level of overall strength of the hull, and, if necessary, develop a technological process for elimination the overall residual bend (deflection). The procedure for determining the parameters of general residual deformations is further complicated by the fact that the maximum inflection (deflection) arrow obtained from the measurement results also includes an elastic component. The developed mathematical dependencies make it possible to exclude from the maximum arrow of bend (deflection) obtained as a result of measurements the elastic component caused by the load acting on the ship’s hull. A device has been developed for recording deviations of the axis of a deformed ship’s hull from the initial (nondeformed) position. The new measurement technique and this device will allow measurements not only when the vessel is on a slip or in a dock, but also afloat at quay wall. Due to the fact that the geometric characteristics of the section along the length of the ship’s hull change, the optimal number of measured sections (5–7) in the area of the cylindrical insert is justified, with the length of each section a multiple of the frame spacing. An example is given of calculating the ordinates of the residual curved axis of the body based on the measurement results and determining the curvature in each of the deformed sections.