Effect of ground heterogeneity on the seismic surface-wave response of a multi-storey building

Near-surface soil heterogeneity can significantly influence seismic surface-wave transmission and building response. This study evaluated the effect of soil stratification on the floor-by-floor dynamic response of a multi-storey building subjected to Rayleigh-type excitation. Two three-dimensional PLAXIS 3D soil-structure interaction models were developed: a homogeneous profile and a heterogeneous profile consisting of loam and gravel layers with different stiffness, density, and wave velocities. The 200 × 100 × 50 m domain contained 44,836 tetrahedral elements and a 24 × 24 m, 27 m high building with a 3 m basement. Viscous absorbing boundaries, Newmark time integration, and a 10 Hz harmonic displacement applied for 5 s were used. In the homogeneous model, peak displacement amplitudes ranged from 0.90 to 3.15 mm, whereas the layered model produced 0.76–2.59 mm, corresponding to reductions of 13.16–26.55%. Velocity reductions ranged from 12.00% to 56.37%, with the largest decrease on the seventh floor. The non-uniform response along the building height reflects combined soil-structure interaction effects. The results show that homogeneous-ground assumptions may misestimate building vibrations and that site-specific stratification should be represented in seismic surface-wave analyses.

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