The goal of this research is to address concerns about the suitability of using rocking shallow foundations for bridges. The research quantifies how combined moment, and shear, and axial loading affect behavior rocking behavior and illustrates the beneficial energy dissipation and self-centering characteristics that shallow foundations can introduce to the system. Due largely to these self-centering characteristics, rocking foundations appear to be quite resistant to instability as a result of P-∆ effects
Even if design guidelines were made to allow for rocking and the design philosophy included using shallow foundations as a mechanical fuse limiting structure loads, allowing soil to yield under a shallow foundation and mobilization of the moment capacity of the footing will not be used unless there is an accurate method of analysis. For this reason, existing elements and analysis tools available in OpenSees were exercised to show that they can reasonably predict the behavior of rocking foundation systems.
Several centrifuge tests were carried out at UC Davis on models of single-column bridge bents on shallow foundations. The experimental data from these tests along with the experiments done by many researchers (Gajan et al. 2005; Taylor et al. 1981; and Faccioli et al. 2001; and others) on the load-displacement behavior of shallow foundations and soil-structure interaction shed light on the rocking behavior of a shallow foundation and its influence on a bridge superstructure. The experimental data were then used to exercise and verify finite element tools for a range of structures on rocking foundations.
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