Dynamic stiffness and kinematic response of bridge embankments

Dynamic stiffness of bridge embankments and their kinematic response when subjected to harmonic unit motions at the base are investigated. These quantities furnish global information on the seismic response of embankments that may be used, according to a substructure approach, to include effects of abutment-embankment interaction in the seismic analysis of bridges. Embankments with trapezoidal cross sections of different height and with different length and longitudinal slope are considered in the analyses which are performed in the frequency domain by means of a 2D higher order model developed by the authors. The soil material properties and the inclination of the cross section slopes are selected within common ranges in practical applications. The presence of rigid abutment is considered. The effective length and the possibility of modeling only limited sections of the embankment are discussed. The effects of the embankment height and the longitudinal slope are also addressed. Results point out that the longitudinal slope produces local vibrations that affect the embankment behaviour for excitations close to the fundamental frequencies. The embankment height is the parameter that mainly affects the system dynamics by changing both impedance and kinematic response functions.