PSI - Issue 78

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

2137

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0 4.00 8.00 12.00 16.00 20.00 24.00 28.00 32.00 36.00 40.00 TIME (s) 4

0 4.00 8.00 12.00 16.00 20.00 24.00 28.00 32.00 36.00 40.00 TIME (s) 6

TIME (s)

2

Figure 5. 6 acceleration time histories calculated on the ground surface with best fitting procedure with respect to 10% exceedance acceleration spectrum as given in Figure 4a based on 10% exceedance probability. 4. Microzonation for Ground Shaking Intensity In the previous microzonation surveys by the authors (Ansal et al. 2004, 2005, 2009, 2010, 2019; Studer and Ansal, 2004), the superposition of two parameters is used to estimate the ground shaking intensity, the first parameter was the peak spectral accelerations for the short period calculated based on equivalent (average) shear wave velocities (V s30 ) for each soil profile using the relationships proposed by Borcherdt (1994). The second parameter is the average spectral accelerations between 0.1 and 1. sec periods calculated based on site response analysis. The microzonation maps are based on the division of the investigated urban area into three zones (as A, B, and C) with respect to the frequency distribution of the selected ground shaking parameters as shown in Figure 6. The main aim was to avoid using numerical values and to be able to use for areas with differences in seismic hazard levels.

Figure 6. Relative microzonation approach adopted with respect to the statistical distribution Another topic in the scaling of input acceleration time histories is the local hazard level, in general it is preferred to adopt the hazard level corresponding to a return period of 475 years. For certain districts, a higher hazard level may be preferred. It may be necessary to select input motions compatible with higher hazard level. Since the concept of microzonation is based on relative levels of shaking intensity, the distribution of high shaking intensity cells may likely be modified. Structural damage is controlled by three main factors (a)source and path characteristics, (b)local geological and geotechnical conditions, and (c) structural characteristics. The microzonation parameters used by Ansal et al., (2019)