PSI - Issue 70

Aman Kumar et al. / Procedia Structural Integrity 70 (2025) 255–262

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effect is most pronounced in the low-period range (0 – 1 second), where the ground motion is significantly intensified. This amplification occurs because softer soils tend to resonate with shorter-period structures, leading to higher seismic forces and displacements. However, as the period increases beyond 1 second, the amplification effect gradually diminishes. By the time the period reaches 4 seconds, the soil amplification effect becomes negligible, indicating that longer-period structures are less influenced by soil amplification.

Fig. 3. (a) detailing of soil profile (Deep Soil software) and (b) Amplification of ground motion and response spectrum

4.2. Effect on seismic response The pushover curve shows the nonlinear capacity of the building. The y-direction pushover curve is slightly above the x-direction pushover curve, showing that the building capacity is higher in the y-direction than in the x-direction, as shown in Figure 4. The ultimate base shear capacity of the building is slightly higher (55 kN) in the y direction than in the x direction. The time history analysis of the building has been performed by considering the three modified ground motions at the bedrock level and amplified ground motion at the surface level. Average Base shear capacity, Roof displacement, and demand ductility are estimated in the x and y directions due to original and amplified ground motion, as presented in Table 1. Spectral displacement values are calculated from the roof displacement in the modal analysis of the building. It has been observed that due to the amplified ground motion, the Base shear value has been increased by 229 kN (1356 to 1585 kN), Roof displacement increased by up to 145 mm (153 to 298 mm), ductility demand increased by up to 1.58 (2.87 to 4.45), and spectral displacement value increased by up to 110 mm (117 227mm). Thus, Soil amplification significantly increased the seismic response of the building. The seismic response of the building in the y direction is lower than in the x direction.

Table 1. Seismic Response of the building Direction Base shear

Roof displacement

demand ductility

Spectral displacement

original

Amplified original

Amplified original

Amplified original

Amplified

x y

1340 1356

1540 1585

0.153 0.298 0.146 0.287

2.87 2.72

4.45 4.16

0.117 0.227 0.111 0.219