PSI - Issue 38

Yuichi Shiraishi et al. / Procedia Structural Integrity 38 (2022) 588–595 Author name / Structural Integrity Procedia 00 (2021) 000 – 000

591

4

trough ribs and cross ribs. Loading area B replicate the loading condition which cause fatigue cracking at welded joints between the deck plate and trough ribs. Fig. 4 shows the loading waveform under conducting fatigue test. In static loading test, the specimen was loaded on loading areas A, B and C individually by using three actuators. In fatigue test, the specimen was loaded on three loading areas alternatingly every 90 degrees of loading waveform. Load range of each loading area was 130kN (maximum load was 150kN and minimum load was 20kN) which correspond to maximum axle load 260kN (the load of a set of double tire is 130kN) measured Hanshin Expresssway in Japan [Hanshin Expressway (2017)]. In fatigue test, the loading frequency was from 3 to 4 Hz. Table 1 shows steps of fatigue test. In the

Table 1 steps of fatigue tests

The existing structure (U1) The newly structure (U2)

Steps

Counter measure

Counter measure

Porpose

Porpose

Verification of the preventive countermeasure To cause fatigue cracking Verification of the post countermeasure

retrofit using angles

1

Verification of the preventive countermeasure

the improved structure

2

none

retrofit using angles

3

existing structure, fatigue test was conducted under 3 steps. At first, verification of the preventive countermeasure effect was investigated through conducting fatigue test with angles. Next, fatigue test was conducted without angles, and cause fatigue cracking at welded joints between a trough rib and a cross rib. Finally, verification of the post countermeasure effect was investigated through conducting fatigue test with angles. In the newly structure, verification of the preventive countermeasure effect of the improved structure was investigated through conducting fatigue test still fatigue test was ended. 3. Test results 3.1. Static loading test Fig. 5 shows distributions of differences between maximum and minimum strain obtained through conducting static loading test. The static loading test was conducted before and after retrofitting for the existing structure. Fig. 6 shows distributions of principal stress in a cross rib. Compared loading area A and C, when the specimen was loaded on loading area C where was closer to diaphragms, larger stress was measured than loading area A. Before retrofitting for the existing structure, strain differences were measured about -550 μ ( - 110MPa) and +500μ (100MPa) at gauges No.5 and 6. However, after retrofitting, strain differences were about - 100μ ( - 20MPa) and 170μ (34MPa) at there. These strain differences were about 1/3 or 1/5 of strain differences before retrofitting. Furthermore, before retrofitting, horizontal principal stress which was measured on a cross rib was over ±50MPa. After retrofitting, principal stress reduced to about ±15MPa. For these results, it was confirmed that retrofit using angles can reduce stress around welded joints between trough ribs and cross ribs.

F ig. 5. shows distributions of differences between maximum and minimum strain obtained through conducting static loading test

Fig. 6 . distributions of principal stress in a cross rib