Quantification of Fundamental Frequencies of 3D Basins and Structures and Site–City Interaction Effects on Responses of Structures.

Kumar, Neeraj; Narayan, Jay Prakash

Large-scale commercialization in Indian metrocities has made realtors develop new construction sites by filling land depressions with loose soil, which may behave as small three-dimensional (3D) basins. This study presents the development of empirical relations to predict the fundamental frequency of basins ( F 03 D B ) and structures ( F 03 D S ) on rock for different shape ratios to study the effects of site–city interactions (SCIs) on the response of structures under a double resonance condition. The S-wave responses of the various considered basins, structures, and site–city models are simulated using the finite-difference method. Analysis of the simulation results reveals that the F 03 D B of the basin and the F 03 D S of the structure depend strongly on the shape ratio, on average matching with those obtained using the SV-wave response of the section of the respective basin/structure. However, the spectral amplification factor (SAF) obtained at F 03 D B / F 03 D S for the basin/structure is much larger than that obtained using the SV-wave response of a section of the respective basin/structure. Empirical relations are developed to predict the F 03 D B of basins and F 03 D S of structures in terms of the shape ratio and one-dimensional (1D) fundamental frequency of the respective model. Analysis of 3D SCI effects reveals a reduction of the SAF at the fundamental frequency of the structure in the basin ( F 03 D SB ) with an increase of the number of structures as compared with that at the fundamental frequency ( F 03 D SB ) of a standalone structure in the basin, being on the order of about 60 % in the case of a city with 25 structures. This finding indicates the need for 3D SCI studies in urban environments for cost-effective earthquake engineering.

FINITE difference method; EARTHQUAKE engineering; LANDFILLS; BUILDING sites; TRAVELING salesman problem; URBAN ecology (Sociology)

Pure & Applied Geophysics, 2019, Vol 176, Issue 10, p4477

0033-4553

Academic Journal

10.1007/s00024-019-02158-8