Analytical Investigation of Potential Seismic Damage to a Skewed Bridge

Investigative reports on the 1994 Northridge earthquake in California indicated significant damage experienced by skewed highway bridges. Specifically, the damage sustained by the Pico-Lyons Bridge near Newhall, California, was noted to have been triggered by the skewed geometry of the bridge. In an effort to portray the behavior of this bridge analytically, a series of simulation studies was conducted using nonlinear finite-element analyses. The objective was to demonstrate that certain damage potentials in skewed bridges during earthquakes can be captured analytically. Dynamic time history and pushover analyses were used to capture the behavior of the superstructure of the skewed bridge using the Northridge ground motion record as the input seismic force. Results from the simulation studies showed that potential damage areas, comparable to those reported in the field investigation of the Pico-Lyons Bridge, can be portrayed through analytical modeling. The study also provided the percentage increase in critical stresses in the superstructure of skewed bridges as the angle of skew increases compared with a comparable nonskewed bridge. The study showed that cases in which the angle of skew is approximately 40°, the percentage increase in stress due to the skewness effect at the end girders can be as high as 50–60%.