Dimensional Determination of a Two-Storied Package Rafting Unit Placed on a Solid Basement

Abstract

Two-storied package rafting units (TPRU) are essential for implementation of the concept of environmentally friendly forest transport operation of medium and small rivers' system, which provides commercial accessibility of wood raw materials from the remote forest areas of Russia, and sustainable use of resources. The use of TPRU implies the need of engineering calculations, for instance, to substantiate their dimensions in case of the units formation on a solid basement (at log storage area). Selection of dimensions should be sufficient for the correct assessment of their structural behavior. An additional study, the purpose of which is to obtain dependences for determination of dimensions of TPRU, was proposed to conduct as a result of the literature data analysis. The research method is theoretical. The packages were considered as weightless flexible shells filled up with one type of loose medium. We have validated the capability of use the second order parametric equations of elastics with no inflexion point for describing cross-section of packages. A system of equations that connect the desired dimensions is derived. The analytical solution of the obtained system turned out to be impracticable. A computer algorithm for solving the numerical method was developed and implemented. The calculations were performed by operating with specific characteristics corresponding to the unit area of a separate package. The dependences of specific dimensions of TPRU placed on a solid basement on the shape factor of a separately lying package were obtained by approximating the calculation results. Transition to the absolute values of height, width, and length of the rafting units and the working section length of the external strapping is provided by multiplying the specific characteristics by the square root of the package cross-sectional area. An approximating equitation is also obtained for calculating the absolute value of the working part length of the external strapping by the shape factor and the height of a separately lying package. The approximating dependencies, which allow to determine by the shape factor of a detached package the position of the zero pressure surfaces of a loose medium for lower and upper packages, as well as correlation between the heights of the mentioned packages, were proposed to resolve the issues related to the strength characteristics of a rafting unit under the considered conditions. The determination coefficients of the suggested approximating dependencies have values not less than 0.99. The theoretic data reliability is confirmed by the experimental technique applying the physical models.