On soil-structure interaction in large non-slender partially buried structures

Abstract

This paper addresses the seismic analysis of a deeply embedded non-slender structure hosting the pumping unit of a reservoir. The dynamic response in this type of problems is usually studied under the assumption of a perfectly rigid structure using a sub-structuring procedure (three-step solution) proposed specifically for this hypothesis. Such an approach enables a relatively simple assessment of the importance of some key factors influencing the structural response. In this work, the problem is also solved in a single step using a direct approach in which the structure and surrounding soil are modelled as a coupled system with its actual geometry and flexibility. Results indicate that, quite surprisingly, there are significant differences among prediction using both methods. Furthermore, neglecting the flexibility of the structure leads to a significant underestimation of the spectral accelerations at certain points of the structure.

Filtering effect induced by rigid massless embedded foundations

“…SSI can be thought conveniently, both from a conceptual and computational point of view, as the contribution of two concurrent phenomena (Mylonakis et al, 2006): (i) kinematic interaction, in which a massless foundation modifies the motion of the surrounding soil by means of its sole stiffness and (ii) inertial interaction, in which the motion of the foundation itself is further modified by the D'Alembert forces acting in the structure-foundation system. The distinction between kinematic and inertial effects, which also underlies the substructure method, provides a powerful key to interpretation of SSI problems, as observed in experimental works (Rayhani & El Naggar, 2008), numerical works (Mahsuli & Ghannad, 2009;Politopoulos, 2010;Vega et al, 2013) and field measurements (Stewart, 2000;Kim & Stewart, 2003), where many factors can affect the overall dynamic response of the structure. By focusing on the filtering effect, kinematic interaction has been recognised to play a significant role in the case of both embedded (Avilés et al, 2002;Politopoulos, 2010) and deep foundations (Di Laora & de Sanctis, 2013), for which the foundation input motion (FIM) can differ substantially from the free-field motion recorded at ground surface.…”

Μελέτη Της Επιρροής Της Βελτίωσης Του Εδάφους Στη Δυναμική Αλληλεπίδραση Εδάφους-Θεμελίωσης-Ανωδομής

“…Στη συνέχεια η χρονοϊστορία της επιτάχυνσης στις θέσεις αυτές προκύπτει μέσω του αντίστροφου μετασχηματισμού FFT (Σχήμα 3.8). H προσέγγιση αυτή έχει εφαρμοστεί από επίσης από τουςVega et al (2013) και ο σχετικός κώδικας μπορεί να βρεθεί στο Παράρτημα Α.Σχήμα 3.8 Διάγραμμα ροής υπολογισμού της χρονοϊστορίας απόκρισης με βάση τη μιγαδική συνάρτηση μεταφοράς που λαμβάνεται από αναλύσεις πεπερασμένων στοιχείων.…”