Introduction of seismic-resistant precast/prestressed concrete girder bridges in California

As more is leamed about earthquake mechanics and its effects on structural engineering, the demands on structures for seismic performance have been increasing. From the evolution of a simple equivalent static load of 0.06g in the 1950's to today's sophisticated methodology of response spectral analysis, time history, and ductility response, the general trend points towards an increase in seismic design requirements and an emphasis on the mechanics of resistance. Concurrent with advances in seismic bridge engineering over the last decade, a noticeable decline in the use of composite precast I-girder construction in areas of high seismicity has also occurred. The authors believe that a principal factor in this decline has been the failure to develop bridge systems that are in tune with today's seismic requirements.