Nonstationary seismic response of highway bridges supported on columns

The seismic displacement of a bridge superstructure relative to its substructure (columns) is studied, including uncertainty of the seismic input. The earthquake excitation is modeled as white noise filtered by the Clough-Penzien (1975) filter, in cascade with modulation accounting for seismic intensity nonstationarity. An analytical solution is obtained for the statistics of the relative displacement and its derivatives. These may be used to develop probabilistic seismic response spectra for design.