International Institute of Earthquake Engineering and Seismology Journal of Seismology and Earthquake Engineering 1735-1669 27 2 2025 04 01 Seismic Performance of Mat and Grid Foundations on a Soft Fine-Grained soil underlying an Eight-Story Building 25 33 717345 10.48303/jsee.2024.2042496.1126 EN Javad Jalili Assistant Professor, Geotechnical Engineering Research Center, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran 0000-0001-6840-5221 Mojtaba Moosavi Assistant Professor, Geotechnical Engineering Research Center, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran 0009-0007-2411-8643 Faradjollah Askari Associate Professor, Geotechnical Engineering Research Center, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran 0000-0001-9157-2693 Azadeh Marghaiezadeh Research Expert, Geotechnical Engineering Research Center, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran Journal Article 2024 10 02 <span>In cases of large deformations of the ground underlying a structure, mat and grid foundations are two options to reduce probable differential settlements, due to their rigidity in the perpendicular directions and their relatively larger area compared with single spread foundations. A case study of large settlements of an 8-storey structure resting on soft saturated fine-grained soil due to seismic loading is numerically investigated herein. The foundations were matching in plan dimensions (10*18 m), and the grid foundation was 30 cm thicker than the 60-cm-thick mat, reaching nearly similar volume (110 m3 in the case of grid foundation and 108 m3 in the case of mat foundation). To decide on the more economical foundation type between mat and grid, the amount of reinforcing steel bars and the cost of construction, including concrete molding should be considered. Herein, based only on the amount of foundation settlement, it is shown that the performance of a grid foundation is better than or identical to mat foundations, which makes it an alternative with probably a more economical option to be preferred to mats in the design of foundations in areas of high seismicity. It is also shown that assessment of the frequency content of the input motions by applying the white Gaussian noise added to a sine sweep of frequencies to the model and inspecting the results, is useful in understanding the results.</span>