Simplified approach for design of raft foundations against fault rupture.
Part II: soil¨Cstructure interaction
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I. Anastasopoulos1,2, N. Gerolymos1, G. Gazetas1
and M. F. Bransby2
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1. School of Civil Engineering, National Technical University of Athens,
Greece
2. Civil Engineering, University of Dundee, Scotland, UK
Abstract: This is the second paper of two, which
describe the results of an integrated research effort to develop a four¨Cstep
simplified approach for design of raft foundations against dip-slip (normal and
thrust) fault rupture. The first two steps dealing with fault rupture
propagation in the free-field were presented in the companion paper. This paper
develops an approximate analytical method to analyze soil¨Cfoundation¨Cstructure
interaction (SFSI), involving two additional phenomena: (i) fault rupture
diversion (Step 3); and (ii) modification of the vertical displacement profile
(Step 4). For the first phenomenon (Step 3), an approximate energy¨Cbased
approach is developed to estimate the diversion of a fault rupture due to
presence of a raft foundation. The normalized critical load for complete
diversion is shown to be a function of soil strength, coefficient of earth
pressure at rest, bedrock depth, and the horizontal position of the foundation
relative to the outcropping fault rupture. For the second phenomenon (Step 4), a
heuristic approach is proposed, which ¡°scans¡± through possible equilibrium
positions to detect the one that best satisfies force and moment equilibrium.
Thus, we account for the strong geometric nonlinearities that govern this
interaction, such as uplifting and second order (P−¦¤) effects. Comparisons with
centrifuge¨Cvalidated finite element analyses demonstrate the efficacy of the
method. Its simplicity makes possible its utilization for preliminary design.
Keywords: fault rupture; analytical method; raft
foundation; soil-structure interaction; earthquake
