9415955 Siddharthan Bridge abutments located above the ground water table have performed in an acceptable manner prior to the 1994 Northridge earthquake. However, their behavior in this earthquake was clearly unsatisfactory. The aim of this project is to critically investigate a number of bridge abutments (damaged and undamaged) located in the area affected by the 1994 Northridge earthquake using the ground motions measured in this earthquake. These investigations address the following issues: (1) Why did some of the abutments behave poorly and some not? (2) Is guidelines, and the modified version used b the principal investigators in their recent study adequate? (3) Was there any unexpected contribution from deck- abutment interaction forces? (4) Are there any anomalies between characteristics of Northridge motions and other existing excitation records (e.g. those used in the recent study by the proposer) with respect to their effect on abutment behavior? (5) did higher than normal vertical acceleration component present in the Northridge excitations play a role? ***
