2009 Buchanan Lecture: Jose Roesset: Some Applications of Soil Dynamics

The Spencer J. Buchanan Lecture Series on the GeoChannel is presented by the Geo-Institute of ASCE. For more information about the Geo-Institute: http://www.asce.org/geotechnical-engi...

The 17th Spencer J. Buchanan Lecture in the Department of Civil Engineering at Texas A&M University was given by Jose M Roesset on Nov. 13, 2009.

"Some Applications of Soil Dynamics"

Abstract:

Soil Dynamics is the branch of Soil Mechanics (or in more fashionable modern terms Geotechnical Engineering) that studies the behavior of soil deposits and earth structures subjected to dynamic loads. It originated in the first quarter of the 20th century with the need to understand and eliminate the vibrations of foundations caused by heavy rotating machinery. It has become since an essential component of Earthquake Engineering (recognized even by some structural engineers), and it has found a number of other important practical applications. These include the determination of the dynamic stiffness of different types of foundations subjected to dynamic loads, the study of the effect of local soil conditions on the characteristics of earthquake motions, seismic soil structure interaction analyses, the seismic response of earth structures, the study of vibrations created by construction equipment, such as pile driving machines, or moving loads, and the determination of soil properties in laboratory tests and in situ. In this lecture we will look briefly at some of these applications, their historical background, the present state of the art and basic features of the problem, and some of the research needs.

About Jose M Roesset:

As a faculty member in the Civil Engineering Department of MIT (1964-1978) Dr Roesset conducted roughly half of his research on Nonlinear Structural Dynamics, with special emphasis on Earthquake Engineering, and the other half on what is known now as Geotechnical Earthquake Engineering. His structural work involved studies on inelastic response spectra, development of nonlinear structural models such as the fiber model, assessment of the validity of approximate procedures to derive equivalent inelastic single degree of freedom systems from incremental nonlinear static analyses of frames (later called the push-over method), and development of formulations in time and frequency domains. His work on geotechnical engineering involved first studies of the effect of local soil conditions on the characteristics of earthquake motions (soil amplification) for different types of seismic waves, then the
determination of the dynamic stiffness of mat foundations and single piles, and finally the study of the effects of the soil/foundation flexibility on the seismic response of structures (soil structure
interaction). Much of this work found applications in the seismic analysis and design of Nuclear Power Plants, a hot topic at that particular time, and Dr. Roesset served as a consultant in a number of plants.

At the University of Texas at Austin (1978-1997) Dr. Roesset continued to do some work on nonlinear structural dynamics and on dynamic stiffness of foundations (pile groups in particular) but he devoted most of his research effort to more fundamental wave propagation studies with special application to the nondestructive evaluation of soil deposits and pavement systems. This work was performed in collaboration with Dr. Kenneth H. Stokoe (the sixteenth Buchanan lecturer) and involved on one hand the development of the formulation to interpret the data obtained with the Spectral Analysis of Surface Waves (SASW) method in order to backfigure the variation of soil properties with depth, and on the other the interpretation of the data obtained from Dynaflect and Falling Weight Deflectometer (FWD) tests to determined the elastic properties of pavement layers. The studies in this last case included the evaluation of the effects of the finite width of the pavement and the relative position of the FWD with respect to the edge, and the assessment of the importance of nonlinear soil behavior under large loads, particularly for flexible pavements.


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