Effect of Seismic Demand on Skew Bridge

I found this research article very interesting and useful for most bridge engineers who are working on the bridge design and retrofitting to mitigate the severe effects from Earthquake. The research title and video are "Seismic Displacement Demands on Skewed Bridge Decks Supported on Elastomeric Bearings" The research is introduced and conducted by Prof. Oh-Sung Kwon from U of Toronto, Canana.

Since this type of the bridge is most famous and constructed most in many countries including Thailand due to the feasibility in the construction and economy, the understanding in the behavior of the bridges during Earthquake is very important. Moreover, the current code of practice used in many countries is still very limited e.g. AASHTO LRFD Bridge Design Specification to design this type of skewed bridge subjected to Earthquake. This research is thus very useful in the near future.

In this blog, I will collect more useful information regarding to behavior, design, and analysis of this type of bridges in series starting with the research by Prof. Kwon and will share with you. Please inform me your comments and share your experience about the seismic design of skewed bridges.

The following animation shows the seismic response of a skew bridge. Elastomeric bearings are modeled with elements which can simulate the effects of normal force on sliding resistance. Due to vertical component of input ground motion, the normal force on elastomeric bearings constantly varies affecting sliding resistance. Hysteretic response of elastomeric bearings and abutment (left four figures), and animation of deck displacement (right top) and bridge bearing (right middle) are presented. Based on analyses of two sets of motions, the tentative conclusions are 1) skew angle increases rotational seismic demand, 2) skew angle does not have much effect on displacement demand in skew direction but largely increases displacement demand in the direction normal to abutment, 3) pulse-type near fault motions have much more significant effects than far-fault motions.