Decline rate of

flexural rigidity/%

Maximum of wavelet coefficients

The results of BP neural network testing

1 scale

2 scale

3 scale

4 scale

Predicted value

Relative error/%

15

1.572

2.363

3.260

4.484

15.097

0.65

25

1.585

2.366

3.265

4.504

25.037

0.15

35

1.602

2.370

3.272

4.530

35.087

0.25

45

1.624

2.375

3.281

4.565

45.025

0.06

55

1.656

2.383

3.293

4.615

55.057

0.10

65

1.704

2.394

3.311

4.691

64.966

−0.05

75

1.787

2.413

3.342

4.820

74.978

−0.03