Trans RINA, Vol 154, Part A2, Intl J Maritime Eng, Apr-Jun 2012
the lateral plating edges should be considered for the FS series whose different error is around 13%. But for the BS, LS and US series, this difference is less than 7%. It would be too optimistic if the displacement in the z direction is constrained at the interaction of the plate and the frames. This influence on wide panels is bigger than narrow panels. For the wide panels, the constraint in the z direction on the frame affect significantly the ultimate strength for the FS and BS series, but slightly for the LS and US series.
The average stress-shortening curves Figure 30 Equivalent stress distributions for 2bay2-C8 and ultimate
strength with 1 bay model is very different from the other configurations which cannot account for the interference between adjacent panels. The asymmetrical
collapse
modes occur in the 1+1 bays with simply or restraint boundary condition in the longitudinal direction, which would increase the modelling uncertainty [23]. bay and 1+1 bays models are not
The 1
ultimate strength tests of stiffened panels. To reduce the modelling uncertainty for
the 1+1 bays model,
recommended in the
periodical symmetric or symmetric boundary condition should be adopted in the longitudinal direction.
The 3 bays and 1/2+1+1/2 bays models allow to have realistic results by
avoiding Figure 31 Equivalent stress distributions for 1bay-C9
problems for the central plates related to eccentricity of load and including the interference
boundary conditions effect between
adjacent panels. The ultimate strength of the 1/2+1+1/2 bays model bigger slightly than the 3 bays model with the same boundary condition. The clamped or restrained boundary conditions in the longitudinal direction have only a minor influence on the panel strength. For the 3 bays model with restrained boundary condition, the side bays collapse instead of the middle bay in some case in the FE analyses and the experiment. Hence, the boundary condition for 3 bays model in the longitudinal direction should be strong enough to avoid the side bays collapse instead of the middle bay.
6.
Figure 32 Side bays collapse mode for 3 bays with restrained boundary condition
5. CONCLUSIONS
The boundary conditions and model geometry affect the collapse behaviour and ultimate strength of stiffened panels. This influence depends on the stiffener type in some
degree. During loading, the stiffness of the
stiffened panels with B0=300 mm is similar for different configurations except in the C9 condition. The FS and US series is more sensitive to FE modelling and boundary condition than the BS and LS series.
When the symmetric boundary condition for stiffened panels is not applied at the lateral plate edges, such as in experiments, the influence by the lack of effectiveness at
2. 3.
7. 1.
REFERENCES
IACS, 2006. Common Structural Rules for Bulk Carriers. International Association of Classification Societies, London
Guedes Soares C., 1988. Design equation for the compressive strength of
unstiffened plate
elements with initial imperfections. Journal of Constructional Steel Research (9), pp. 287-310.
Guedes Soares C., Kmiecik M., 1995. Influence of the boundary conditions on the collapse strength of square plates with initial imperfections.
Marine Technology and ACKNOWLEDGEMENTS
The first author has been financed by the Portuguese Foundation for Science and Technology (Fundação para a Ciência e Tecnologia), under contract SFRH / BD / 65120/ 2009.
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©2012: The Royal Institution of Naval Architects
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