DISPLACEMENT-BASED DESIGN OF SHALLOW FOUNDATIONS WITH MACROELEMENT

The scope of this paper is to demonstrate the utility of macroelement modeling of shallow foundations in performance-based design. We focus on the settlements, horizontal displacements and rotations of a bridge pier founded on a rigid circular foundation on a relatively soft cohesive soil. A newly developed macroelement model is used for the description of the footing-soil system. Its objective is to reproduce the geometric (uplift of the footing) and material non-linearities (soil plasticity) that arise at the foundation level during a seismic excitation. The utility of macroelement modeling resides in the fact that it allows for the execution of a large number of non-linear dynamic analyses of the pier under the horizontal and vertical components of real acceleration time histories as well as under the combination of both. The results concentrate on two main points: the influence of the vertical component of the seismic input motion on the maximum and residual displacements of the foundation and on a discussion of possible correlations between the induced displacements at the foundation level and certain parameters describing the severity of the seismic input motion.