PSI - Issue 64

Ina Reichert et al. / Procedia Structural Integrity 64 (2024) 145–152 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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3. Application For the application, a 2D numerical model is used to firstly artificially generate measurement data corrupted by five different amounts of noise and secondly undergo the FWI procedure considering three different fault sizes and positions under ten variations in sensor distance. The numerical model is a 30 m by 25 m large concrete structure with a grid size of 180 times 153 grid points depicted in Fig. 1, where the fault sizes and positions are listed in Table 1. Extending these 2D investigations into the

Fig. 1. Numerical models of real structure displayed for the shear-wave parameter with fault sizes and positions of a) combination 1, b) combination 2 and c) combination 3

3D space would require original 3D simulations to consider all three dependent dimensions. Also, a significantly larger amount of computing capacity would be needed. As a first approach, the sensor distances determined for the 2D case in one direction could also be used in the orthogonal direction for the 3D case.

Table 1. List of fault sizes and positions for the selected example combinations Combination X-position of center c x [m] Z-position of center c z [m]

Width w [m]

Height h [m]

1 2 3

15.00 15.00 22.50

6.25

2.50 2.50 2.50

7.50 2.50 1.25

12.50 18.75

A defect in the shape of an ellipse made of polystyrene is placed inside the concrete solid and on the outside a surrounding layer of air is modeled. The characteristic material properties of these three materials are given in Table 2.

Table 2. Material properties of the model Material V P [m/s] V S [m/s]

ρ [kg/m

3 ]

Air

332.0

0.0

1.25

Concrete

3934.7

2434.0

2200.00

Polystyrene

462.9

378.0

35.00

Fig. 2. Numerical models of initial structure displayed for the shear-wave parameter with different distances in sensor positions for transmission with a) sensor distance = 1 m, b) sensor distance = 5 m and c) sensor distance = 10 m