Trans RINA, Vol 154, Part A2, Intl J Maritime Eng, Apr-Jun 2012
frames. The frame should be included in the FE model of panels instead of constraint when the width of panels is very large or the stiffness of the frame is not strong enough.
0.0 0.2 0.4 0.6 0.8 1.0
C1
effectiveness at the lateral plating edges during buckling. In fact, the percentage of the total cross-section area with reduced effectiveness due to unsupported transverse edges for the wide panels is lower than for the narrow ones and thus, the expected ultimate load is higher for the wider panels. The ratio of the ultimate strength of B0=1500 mm to B0=300 mm is 1.13, 1.06, 1.04 and 1.07 for the FS, BS, LS and US series. The symmetric boundary condition for stiffened panels is difficult
to
FS2-A3 BS2-A3 LS2-A3 US2-A3
300 600 900 1200 1500 Width(mm)
Figure 15 Ultimate strength of three bays model for C1 1 NODAL SOLUTION
STEP=1 SUB =30 TIME=.133815 UY
Y Z (AVG)
RSYS=0 DMX =.050353 SMN =-.050129 SMX =.00685
X
MAR 16 2011 20:10:57
1 NODAL SOLUTION
STEP=1 SUB =30 TIME=.133815 SEQV (AVG) DMX =.050353 SMN =.582E+07 SMX =.690E+09
Y MX Z X
MAR 16 2011 20:11:11
apply in experiments. For narrow panels, the influence by the lack of effectiveness at the lateral plating edges should be noticed for some configurations, such as the different error for the FS series is around 13% at least in this circumstance.
MN MN
0.8 1.0 1.2 1.4 1.6
MX -.050129 -.043798 BS2-E3 (a) Displacement
0.0 0.2 0.4 0.6 0.8 1.0
-.037467 -.031136 -.024805 -.018474 -.012143 -.005812 .519E-03 .00685 BS2-E3 (b) Equivalent stress Figure 16 At the ultimate limit state of BS2-E3 for C1 C2 .582E+07 .818E+08 .158E+09 .234E+09 .310E+09 .386E+09 .462E+09 .538E+09 .614E+09 .690E+09
FS2-A3 BS2-A3 LS2-A3 US2-A3
300 600 900 1200 1500 Width(mm)
Figure 18 Ratio of the C2 to C1 for 3 bays model
Figure 18 shows the ratio of the ultimate strength of the C2 to C1. It is observed that the mean value and standard deviation are 1.11 and 0.41 considering all configurations. The
commonly bigger than that
ultimate strength in the 3bay-C2 condition is in 3bay-C1 condition.
It
FS2-A3 BS2-A3 LS2-A3 US2-A3
300 600 900 1200 1500 Width(mm)
Figure 17 Ultimate strength for 3bays-C2
The 3bay-C2 configuration is designed to understand the effect of B0 on the ultimate strength of the stiffened panels. To ignore the influence of the frame stiffness and to focus on the effectiveness at the lateral plating edges, the displacement in the z direction is
constrained
between the DD1 and FF1 line at the intersection of the plate and the frames for the 3bay-C2 model. Because the AB and A1B1 edges of the panels are totally free to move out-of-plane and to rotate, the ultimate strength increases slowly with increasing width of the panels for the 3bay- C2 condition as shown in Figure 17. This means that larger panels should be less affected by the lack of
©2012: The Royal Institution of Naval Architects
would be too optimistic if the displacement in the z direction is constrained at the nodes on the DD1 and FF1 line for wide model. The more B0 increases, the bigger the ratio of the C2 to C1 is. The biggest ratio of the C2 to C1 for B0=300 mm and 1500 mm are 1.04 and 1.54. This means that the constraint in the z direction between the DD1 and FF1 line is more significantly for wide models than for narrow models. As the panel width grows, the transverse displacement in z direction is increase as the stiffness of the transverse frame decreases due to the constant cross section with longer span. The influence of the constraint in the frame depends on the stiffener type. The difference between the C2 and C1 conditions with B0=1500 mm is 48%, 21%, 2% and 4% for the FS, BS, LS and US series. 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 symmetric boundary condition is applied on the AB and A1B1 edges of the stiffened panels for the C3 and C4 condition. This avoids the transverse plating edges to move out-of-plane and to rotate. The magnitude of the ultimate strength is almost the same with increasing the
A-73
Su/Syp
Su/Syp
C2/C1
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