PSI - Issue 68

Akito Tabata et al. / Procedia Structural Integrity 68 (2025) 415–419 A. Tabata et al. / Structural Integrity Procedia 00 (2025) 000–000

417

3

was initiated from HAZ of the deck plate. The application of the developed steel is expected to suppress the crack initiation of rib-to-deck welded joints.

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Figure 3. Results of the through-deck plate crack reproduction.

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Figure 2. Evolution of strain with time and definition of N 5% .

3. Verification of Effectiveness by application of developed steel 3.1 Experimental procedure

For the purpose of Verification of Effectiveness by application of developed steel, the fatigue tests were conducted using specimens simulating rib-to-deck welded joints. Figure 4 shows a sketch of the test specimen and loading point. The test specimen is composed of deck, U-rib and transverse-rib for double-sided fillet welding. Deck plate is 16 mm or 25 mm thick, U-rib is 6 mm thick. The 490 MPa class steel plates with the chemical composition shown in Table 2 were prepared for the deck plate. The joints of rib-to-deck were welded so that the penetration depth becomes 75% or more of the rib thickness. Figure 5 shows test apparatus. Repeated compressive stress is applied to the deck part by the actuator installed on the top, and repeated bending stress is applied to rib-to-deck welded joints. The load was controlled to a stress ratio of R=0.1, and the cut-off threshold was set to 10 million cycles .

Table 2. Chemical composition of deck plate (mass%) C

Mn

Cu+Si +Ni+Cr

Others

Conventional

0.12 - 0.16 0.05 - 0.06

0.95 - 1.34 1.52 - 1.56

0.20 - 0.35

P, S*

Developed

0.97 P, S, Nb, Ti *Nb and Ti added to some steel materials.