Linear Dynamic Analysis and Design of Raft Foundation considering Long-Term Deflection and Uplift Check

Abstract

The Mat or Raft Foundations are widely used these days because we cannot use isolated footings and combined footings everywhere. As the spacing of the column is not uniform in the actual structures it may result in large uneven settlements at the base of the high-rise buildings. In a Mat foundation load from the superstructure is distributed evenly on the soil and uneven deflection is eliminated. Mat or raft foundation can be used with drops or without drops and with beams or without beams. For structures built on low-bearing capacity soil raft foundations, it is a good alternative as it reduces the settlement by distributing loads from super-structure to very large. In this study, the analysis and design of Mat Foundation for a G+7 story building are done by considering long-term deflection and uplift pressure accounts. For this study, Etabs v19.1.0 and Safe v20.0.0 software is used. The analysis is done by performing Response Spectrum Analysis or Linear Dynamic Analysis. After the analysis, results are collected in terms of short-term deflection, Uplift Pressure, long-term deflection, and punching shear and compared with permissible limits specified by the code IS 1904 (Part-1):1986. Results show that all values like deflection, uplift pressure and punching shear are under the permissible limits.