PSI - Issue 57

Qingyang Wei et al. / Procedia Structural Integrity 57 (2024) 262–270 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

264

3

The liquid penetration tests were also applied to where cracks were found to characterize the propagation directions and sizes of fatigue cracks.The details of a typicalcrack and the penetration test are shown in Fig. 1 (b) and Fig. 1 (c), respectively. After a comprehensive analysis, the detection and evaluation institutions concluded these fatigue cracks would not have a significant impact on the steel bridge in the short term. Nevertheless, the implication of this case is to develop accurate dynamic detection methods and even monitoring methods for crack -prone locations to find similar cracks as early as possible. Preliminarily, the authors try to establish some damage features that are sensitive to fatigue cracks with these quite small sizes in a numerical way. The numerical model of the Türr Istvan bridge is prepared to investigate the dynamic responses and dynamic properties of the deck system with different fatigue crack sizes. Part of the entire bridge is modelled because of the repeatability of the deck system along the longitudinal direction. The numerical model is constructed using finite element software ANSYS and is presented in Fig. 2 (a). The model is constructed with a total of 40 531 eight-node shell elements and a totalof 120 292 nodes. As shown in Fig. 2 (b), the mesh around the crack is densified to better set the different crack sizes. The width of the vertical rib is 150 mm, and the depths of the fatigue crack are set to the levels of 0, 20, 60, 100, and 140 mm. Some key geometry and material parameters are listed in Table 1. The cross girders are vertically and horizontally constrained at the positions contacted with the main truss girder. 2.2. Numerical modeling

Fig. 2. (a) Finite element mesh of the steel bridge; (b) crack details.

Table 1. Parameters of the numerical bridge model.

Parameter types

Parameter values (units)

Spacing of cross girders

5.2 (m)

Width of decks

15.96 (m)

7850 (kg/m 3 )

Density

Modulus of elasticity

210 (MPa)

Poisson's ratio Damping ratio

0.3

0.03