PSI - Issue 19

Yoichi Yamashita et al. / Procedia Structural Integrity 19 (2019) 123–129 Yamashita et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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between fatigue crack growth rate and apparent stress intensity factor range assessed by the fracture mechanics based crack closure model. Here, the model concept is that the gourd-shaped-insert-plates are modeled as spring elements to generate crack closure concentrated force by sticking to crack faces due to their gourd-shape. As a result, the arrester reduces stress intensity factor range and gives the low fatigue crack growth rate. In this model, stress intensity factor subjected to concentrated crack closure force on crack surfaces can be calculated for compact tension specimen (Tada et al. 1973) and also crack opening profile with and without concentrated crack closure forces can be assessed based on Paris’ reciprocal theorem (Paris 1957).

Fig. 4.Fatigue crack growth rate test results with and without “ gourd-shaped-insert-plate ” .

4. Real size test using mockup of steel bridge deck

4.1. Mockup test procedure

To demonstrate the performance, reliability and construction of the crack growth arrester using the gourd-shaped insert plate, a fatigue crack growth test was performed using the mockup of steel bridge deck. Recently many cracks can be inspected in the existing steel bridge decks in the field. Welds of steel bridge decks are one of the main targets to apply the crack growth arrester using the gourd-shaped-insert-plate. The real-size steel bridge deck was manufactured and constructed to conduct the mockup test as shown in Fig. 5. In Fig. 5, the mockup test specimen is set up upside down in comparison with the real field application. Using the hydraulic jack, the cyclic loading of 70 kN is applied to the mockup specimen through gum plate simulating a single wheel loading of heavy vehicles. First, as shown in Fig. 6, a slit was processed to the weld of deck plate and U-rib to prepare the fatigue pre-crack at the edge of the slit by the cyclic loading. And three gourd-shaped-insert-plates were installed to the fatigue pre crack as shown in Fig. 6. Then fatigue loading restarted to assess the performance of the crack arrester.