Abstract
This paper investigates the local strength of reinforced-concrete slabs in a pontoon of the composite floating dock under uniform hydrostatic load. A refined approach was applied to calculate the reinforced-concrete slabs considering the difference in the mechanical characteristics of concrete exposed to stretching and compression. The length of the zone of fixation that impacts concrete compression and stretching has been determined, which is 0.22 lengths of the short side of the rectangular slab. To this end, preliminary calculations of stresses in slabs made from a non-composite homogeneous material were performed, at different sizes of thickness and ratios of the slabs’ side lengths. A finite-element model of the reinforced concrete slab was built, with its reinforcing elements in the longitudinal and transverse directions. The model accounts for differences in the mechanical characteristics, which are set separately for the compressed and stretched regions of concrete. The stressed-strained state of rectangular reinforced concrete slabs has been estimated for the case of complete immersion of the pontoon in quiet water under the influence of uniform hydrostatic pressure, without taking into consideration possible dynamic loads. When simulating the bottom slabs, the length of the larger side of the supporting contour was taken equal to the distance between the longitudinal walls, based on the structural size of the dock. The length of the short side varied multiple to the longitudinal quad, making it possible to acquire data for a wide range of side length ratios, from 3.3 to 1, most characteristic of ship structures. The compressed and stretched areas of concrete were simulated separately, with the mechanical characteristics of strength and rigidity corresponding to the materials used in the construction of floating docks. The charts of maximum stresses in concrete and slab reinforcement depending on the length of the short side of the supporting contour have been built. This has made it possible to determine the optimum width of the slab, which is equal to 3 m for the considered structure under predefined loading. The applied approach makes it possible to optimize the size of such structures in terms of weight and material consumption
Highlights
Shipyards often produce various floating structures for their internal operations
The high mechanical properties of steel allow it to be used for structures of any size, while the minimum weight of the dock is achieved per 1 t of its carrying capacity (0.6...1.0 t)
Stress distribution diagrams: a – a slab measuring 200 × 3,000 × 7,000; b – a slab measuring 120 × 3,000 × 7,000; c – a slab measuring 160 × 3,000 × 7,000 The above diagrams demonstrate the distribution of areas of1t6h-Ae-IcIoI mpressePdrotaenctdivteelnayseilre- z1o0nmems for slabs made from a homogeneous isotropic material does not depend on thickness at deviations within 25 % of the reference value of 160 mm, which covers almost the entire range of thickness used in practice. slabFs i1g61. 024-Ams-hmIIoIwths2i2ca-knA-wIeIxiItahPmrdopitlfeefcetirovefentltahyaeesrpe-se1tc5itmmraamttiioons. diagrams for
Summary
Shipyards often produce various floating structures for their internal operations. For example, floating docks for docking, repairing, or maintenance of vessels, floating cranes, landing stages, and pontoons to ensure the workflow and mooring of small auxiliary vessels, tugs, and working boats [1]. The high mechanical properties of steel allow it to be used for structures of any size, while the minimum weight of the dock is achieved per 1 t of its carrying capacity (0.6...1.0 t) This predetermines the possibility of widespread use of welded joints, providing high manufacturability, the required strength, and water resistance. The use of concrete reinforced with mesh, fibers, or conventional round rods as a shipbuilding material has made it possible to significantly reduce the cost of manufacturing the structures In this case, their weight is much lar ger (1.6 tons per 1 t of carrying capacity), the impact stability of such elements is insufficient, which necessitates frequent repairs of the top layer of concrete. To achieve the set aim, the following tasks have been solved: – to perform the preliminary calculation of slabs made from a non-composite homogeneous material in order to determine the boundaries of the stretched and compressed zones at different values of thickness and ratios of the sides’ lengths; – to estimate the bottom’s composite slabs under the influence of hydrostatic pressure at the complete immersion of the dock, without taking into consideration possible dynamic loads at different ratios of the sides’ lengths
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