PSI - Issue 78

Atilla Ansal et al. / Procedia Structural Integrity 78 (2026) 2133–2140

2135

to use at least 20 acceleration time histories in a site response analysis to minimize the variations in the calculated results that may be due to the selected number of input motions.

0.6

0.6

21 Input motions

23 Input motions

0.5

0.5

0.4

0.4

0.3

0.3

0.2

0.2

SPECTRAL ACC.(g)

0.1

0.1

0

0

0

0.5

1

1.5

2

2.5

3

3.5

4

0

0.5

1

1.5

2

2.5

3

3.5

4

PERIOD (s)

PERIOD (s)

Figure 2. The average acceleration spectrum calculated for the different number of input acceleration time histories along with ±1 standard deviation on average spectra.

EW (Silivri)

0.014

RECORDED 1D (Equivalent Linear) 3D(NONLINEAR)

0.012

0.01

0.008

0.006

0.004

0.002 Spectral Acceleration (g)

0

0

0.5

1

1.5

2

2.5

3

Period (sec)

Figure 3. Comparison 1D and 3D and observed acceleration spectra on the ground surface in the case of M L =5.7 26/09/2019 Silivri Earthquake

As shown in Figure 3, the effects of multidirectional analysis by taking into consideration all strong motion components (EW, NS, V) at the engineering bedrock level indicate the modelling accuracy improvement in comparison to 1D analysis (Sadeghzadeh and Ansal, 2023). For site response analyses the controlling factors are the variation of shear wave velocity and thickness of the soil layers and the depth of the engineering bedrock encountered at the site. To evaluate effects of variability for these factors Monte Carlo simulations are used assuming the assigned shear wave velocities are mean values, and the range