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Finite element analysis of transverse strength of bulk carriers

introduction

in order to ensure that the hull structure of bulk carriers has the ability not to damage or deform too much during normal use and a certain service life, it is necessary to calculate the transverse strength of the hull. At present, There are few literatures using the direct method to calculate the transverse strength [0. According to the ocean classification requirements of China Classification Society, this paper calculates the transverse strength of a bulk carrier under five working conditions: heavy ballast, general ballast, compartment full load, uniform full load of heavy cargo and uniform full load of light cargo. According to the guide for direct calculation and analysis of bulk carrier structure of China Classification Society The direct calculation method is applied to the strength comparative analysis of the main components in the cargo hold area

1 hull description and finite element model

1.1 hull description

20000 DWT bulk carrier, the hull is made of CCSA grade steel The cargo hold area is a single shell and double bottom structure, with a frame spacing of 700 mm; The height of double bottom is 1200 mm, and the spacing between strong frames is 2500 mm; There are also 5 double-layer bottom longitudinal analysis Total length of the ship: l=145.0 m, shape width 8=21.2 m, shape depth d=12.6 m, structural draft ds=8.2 m, square coefficient cb=0.826

1.2 because only one direction working finite element model is required

when using the three-dimensional finite element model to calculate the transverse strength of the main components of the bulk carrier, the model range is a half width model, including 1/2 cargo tanks +1/2 cargo tanks in the cargo tank area in the ship, and the longitudinal range of the compartment model is from the rib. This method is suitable for fr70 to the rib fr122 when the lightweight design requirements are combined with the variability of different components; The vertical range is the depth of the ship All hull components are simulated by plate or beam elements The finite element model is shown in Figure 1 The coordinate system adopts the right-hand coordinate system, the origin is located at the center line of the bottom of the F70, the bow of the x-axis is the positive direction, the port of the y-axis is the positive direction, and the z-axis is the positive direction

Figure 1 Schematic diagram of the finite element model

1.3 boundary conditions

both ends of the model (referred to as a-end and b-end for short) and the mid longitudinal section (CL) need to be constrained, and the detailed boundary conditions are shown in table 1

1.4 calculation condition and load linear rotation combined friction and wear test machine load

because the transverse strength calculation only considers the influence of cargo pressure in the cabin and outboard water pressure, the calculation condition is selected according to the loading manual Take five working conditions of heavy ballast, general ballast, compartment full load, uniform full load of heavy cargo and uniform full load of light cargo for calculation The specific calculation conditions are shown in Table 2

2 calculation results

in this paper, the numerical calculation is carried out under five working conditions and considering the outboard water pressure. The maximum stress of the plate element is shown in Table 3, and the maximum stress of the beam element is shown in Table 4

3 conclusion

based on the establishment of the finite element model, this paper calculates the transverse strength of the bulk carrier under five working conditions: heavy ballast, general ballast, compartment full load, uniform full load of heavy cargo and uniform full load of light cargo. From the calculation results, the two working conditions of heavy ballast (plate element) and compartment full load (plate element and beam element) are dangerous loading conditions, which should be paid attention to in the actual loading Under the condition of heavy ballast, the stresses of the ship's bottom plate, inner bottom plate, side outer plate and transverse bulkhead are relatively large, while under the condition of compartment full load, the stresses of the deck, transverse skeleton and longitudinal skeleton are relatively large Therefore, the design of bulk carriers should focus on two kinds of heavy ballast and compartment full load. 3. The samples should be pretreated at 23 ℃ and 2 ℃ for 24 hours (end)

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