Page 182 - Marine Structural Design

158 Part II Ultimate Strength

Table 9.2 Dimensions and Test Results for Small Scale Test Specimens
Specimen Outer Wall Length Initial Load Young's 0.2%Yield Ultimate Buckling
Number Diameter Thickness L(mm) Deflection Eccentricity Modulus Strrss Load Mode
D(mm) t(mm) a0 (mm) e/D Otpffmm) (Wmm) (tonton)
HA0 97.0 1 .O 1.430 0 19,645 35.25 7.51 DENT
HA2 97.0 1 .o 1,635 0.43 % 19,645 35.25 5.75 DENT
HA3 97.0 1 .o 895 0.13 1116 19,645 35.25 9.78 DENT
HA4 97.0 1 .o 605 0.25 1/16 19,645 35.25 10.08 DENT

HBI 97.4 1.2 1,635 0.10 1/32 19,616 37.50 9.90 DENT
HB2 97.4 1.2 1.430 0.61 1/16 19,616 37.50 9.10 DENT
HB3 97.4 I .2 1,430 I .02 I /8 19,616 37.50 7.95 DENT

HCl 98.2 I .6 1,430 0.44 1/32 19,160 37.m 13.76 DENT
HC2 98.2 1.6 1,430 0.64 I116 19,160 37.00 11.90 DENT
HC3 98.2 1.6 1,430 1.40 1 18 19.160 37.00 9.99 cos

HDI 100.0 2.5 1.430 0.73 1/32 18,109 33.00 19.70 DENT
HD2 100.0 2.5 1,430 0.63 1116 18,809 33.00 17.95 DENT
HD3 100.0 2.5 1,430 0.87 1/8 18,809 33.00 14.95 DENT
HD4 100.0 2.5 1,635 I .44 1 14 18,809 33.00 13.46 COS
ms 100.0 2.5 895 0.35 1132 18,809 33.00 26.85 cos
HD6 100.0 2.5 575 0.35 1116 18,809 33.00 30.55 cos

BAl 97.0 1 .o 650 - BENDlNG 19,645 35.25 2.75 DENT
BB 1 97.4 I .2 650 BENDING 19,616 37.50 3.09 DENT
892 91.4 1.2 650 ___- BENDING 19,616 37.50 3.05 DENT
BC 1 98.2 1.6 650 ____ BENDING 19,610 37.00 4.68 DENT
BC2 98.2 1.6 650 BENDING 19,610 37.00 4.66 DENT
BDI 100.0 2.5 650 --_- BENDING 18,809 33.00 7.84 DENT
Test specimens of alternative sizes are also tested. The inner diameter is kept as 95 mm, and
the tube wall thickness varies as 1.0, 1.2, 1.6, and 2.5 mm. The D/t ratios of these test
specimens then vary between 40 and 97, and the correspondence with bracing members in
existing semi-submersible drilling units is not especially considered. The thickness near both
ends is not increased. The dimensions of small-scale test specimens are shown in Table 9.2
along with material properties and experimental results.
9.2.2 Material Tests
The large-scale test specimens were fabricated by welding the circular that has been bent from
flat plate. To avoid the effect of residual stress on the measured material properties, 4 pieces of
tensile test specimens were cut from the side opposite to the weld line. From the tensile tests,
the measured Young's module is E=21180 kgf/mm2 . The Poisson's ratio is v = 0.32. The
measured yield stress (corresponding to 0.2% offset strain) is: o,, = 34.55 kgflm . The
nominal stress-strain relation from the material is shown in Figure 9.2. The small-scale test
specimens consist of four different D/t ratios, namely series A. B, C and D. Due to the lack of