Seismic response of soil-pile raft-structure system

Abstract

This paper presents an initial effort to investigate seismic response of soil-pile raft-structure system considering soil-structure interaction effect. In general, structure and piled raft under seismic load are designed considering fixed base condition. However, soil flexibility may result significant changes in the response of soil-pile raft-structure system. The study considers one storey system consisting of a mass in the form of a rigid floor slab supported by four columns. The piles are modelled by beam-column element supported by laterally distributed springs and dampers. This simple model used in present study is adequately tuned to exhibit reasonably accurate dynamic characteristics while compared to the existing well accepted methodologies. The study shows that soil-structure interaction leads to considerable lengthening of period though the lateral shear in columns are not significantly changed. However, the shear in piles is significantly increased due to SSI effect as inertia of the considerable foundation mass contributes to this increase in shear of pile. Thus, neglecting SSI may lead to unsafe seismic design of piles. A parametric study encompassing feasible variations of parameters is made under spectrum consistent ground motion. Effect of uncertainty in the soil subgrade modulus on the pile and column response variability is also studied.

Keywords:

• piled raft
• soil structure interaction
• seismic base shear
• fixed base
• natural period
• uncertainty

Additional information

Notes on contributors

Rajib Saha

Rajib SAHA. Assistant Professor of Civil Engineering department in National Institute of Technology Agartala, India. Presently pursuing PhD at School of Infrastructure, Indian Institute of Technology Bhubaneswar as a sponsored research scholar. Prime research interests: dynamic soil-structure interaction and its effect on behaviour of structures, behaviour of piles under static as well as dynamic loading and geotechnical earthquake engineering.

Sekhar Chandra Dutta

Sekhar Chandra DUTTA. Professor and Head of School of Infrastructure in Indian Institute of Technology Bhubaneswar. PhD in Structural Engineering from Indian Institute of Technology Kanpur, India in the year of 1996. Recently completed prestigious Fulbright-Nehru Senior Research Fellowship program at University of California, Davis. Published around 62 technical papers in various peer reviewed journals of international and national repute and received a few awards in recognition of his research contribution. Main research interest: structural dynamics and earthquake engineering, inelastic seismic behaviour of structures, seismic behaviour of asymmetric structures, vulnerability of non-engineered structures under natural disasters, soil-structure interaction, behaviour of masonry structures under seismic forces.

Sumanta Haldar

Sumanta HALDAR. Assistant Professor of School of Infrastructure in Indian Institute of Technology Bhubaneswar. PhD in Geotechnical Engineering from Indian Institute of Science Bangalore, India in the year of 2008. Published around 15 technical papers in various peer reviewed journals of international repute. Main research interests: energy geotechnics, soil-structure interaction, probabilistic geotechnics, geotechnical earthquake engineering, computational geomechanics.