Reliability based optimization of structures under seismic excitation

Summarization: Retaining systems are widely used worldwide for serving various purposes in struc-tures and infrastructures (embankments, bridges, ports, etc). The seismic response of various types of walls that support a single soil layer has been examined by a number of researchers in the past. Nevertheless, the dynamic interaction of the retaining walls with the structures that they are usually retained has not been investigated yet. It is evident, however, that during a seismic event the dynamic response of each component of this complex system (wall, soil, and superstructure) may affect substantially the response of the rest, and vice versa. The phe-nomenon of dynamic wall–soil–structure interaction (DWSSI) is a rather complicated issue that includes: (a) the dynamic interaction between a wall and a retained single soil layer, and (b) the "standard" dynamic soil–structure interaction (DSSI) of a structure with the underly-ing soil. In the present study, using numerical two-dimensional simulations, the influence of the wall characteristics (flexibility and smoothness) and its distance from the structure on the soil impedances (springs and dashpots) and on the distress of a cantilever wall are addressed. Emphasis is given on the variation of the soil impedance with the distance from the wall and with the exciting steady-state frequency. Subsequently, a structure founded on the retained soil is included in the numerical models, as a single-degree-of-system (SDOF). Despite the fact that there exist many open issues, the numerical results of the current study provide a clear indication of the direct dynamic interaction between a retaining wall and its retained structures. This justifies the necessity for a more elaborate consideration of these interrelated phenomena on the seismic design not only of the retaining walls but of the nearby structures as well, since the aforementioned dynamic interaction issues are not considered with ade-quate realism in the modern seismic norms.Παρουσιάστηκε στο: Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineerin