SSI Bridge 2: Evaluation of Soil Structure Interaction Effects on PNW Bridges
PI: Ben Mason (OSU), ben.mason@oregonstate.edu
Co Investigator: Andre Barbosa (OSU)
Dates: 07/01/2013 – 6/30/2015
Final Project Report: PacTrans-25-OSU-Mason
The Pacific Northwest (PNW) is prone to large subduction zone earthquakes as well as smaller, shallow, crustal earthquakes. The effects of these types of earthquakes on PNW bridges is not well understood – especially the effects of the large magnitude, long-duration subduction earthquake motions. In this project, we will solve the following problem: How will typical bridges in the PNW respond during impending earthquake events? The term “typical bridges” here is meant to imply the majority of the bridge stock in the PNW that has not been subjected to rigorous seismic analysis and design. Typical bridges are extremely important, because they account for the majority of the PNW’s bridge stock, and they are critical for the lifeline routes after the impending earthquake occurs. In summary, this work will eventually lead to guidance for designing and retrofitting typical bridges in the PNW, and this guidance will be critical for ensuring that our transportation corridors remain functional after the impending event. This, in turn, will improve the safety of the PNW’s typical bridge stock as well as the overall community livability and economic viability of the PNW following the impending earthquake. PacTrans also funded the first year of this work. In this first year, the project has developed a comprehensive soil-bridge model, which was designed to represent a typical PNW bridge. The project performed analysis of the bridge using a suite of 14 earthquake motions. Seven of the motions were recorded during shallow, crustal earthquakes, and the other seven motions were recorded during the recent subduction zone earthquakes in Chile and Japan. The analysis is showing key differences between the soil-bridge response during the subduction zone earthquakes versus the shallow, crustal earthquakes. In particular, the demands on the soil-bridge system are higher during the subduction zone event. We currently have an MS student finishing a thesis on this project and we are planning on writing a journal paper based on these results.
