University of Washington

• Project: Media Filter Drain: Modified Design Evaluation • PIs: Cara Poor and Liv Haselbach (WSU) The Washington State Department of Transportation (WSDOT) wishes to modify the media filter drain (MFD) design by changing the crushed gravel specification used in the mix. In order to gain approval from the Washington State Dept of Ecology (Ecology) and incorporate into their standard specifications, metal removal rates for the new design need to be compared to the old design based on accepted stormwater doses. The objectives are to test modified and existing MFD mix designs in laboratory experiments for dissolved metals removal and compare these results to determine if there is any statistical difference in the removal rates between the two, and to complete a life cycle analysis on the modified design based on estimated long term high loadings and expected capacities for the media. This will provide WSDOT with a more representative design life of the modified MFD mix design. -• Project: Meeting the Demands of Modern Grade Separation and Earth Retention: Characterization of Frictional Interference in Closely-Spaced Reinforcements in MSE Walls • PI: Armin Stuedlein (OSU) The use of reinforced earth in the United States began in 1972; since then, Mechanically Stabilized Earth (MSE) walls have grown in popularity, and can be found along nearly every state and interstate highway corridor. Due to their inherent flexibility, MSE walls are being constructed to greater heights, in nonlinear geometries, with multiple tiers and with very high reinforcement spacing. For example, the four-tier West MSE wall at Sea-Tac International airport was recently constructed to 46 m height, and is now the tallest wall in the Western Hemisphere. Tall walls (i.e., greater than 15 m in height) will proliferate due to increasing urbanization, rightof-way issues and wetland mitigation; in other words they offer a sustainable alternative to conventional grade separation, due to reduced mining and hauling of earth materials and reduced footprint. However, our understanding of the working stress behavior, including reinforcement strains and displacements, of tall, single and multi-tier walls is unsatisfactory. The research proposed herein aims to address one of several knowledge gaps in the understanding of tall MSE wall behavior: prediction of reinforcement loads impacted by frictional interference of closely-spaced reinforcements associated with tall walls and/or walls in seismically active regions. -• Project: SSI Bridge: Evaluation of Soil-Structure Interaction Effects of PNW Bridges • PIs: Andre Barbosa and Ben Mason (OSU) The Pacific Northwest (PNW) is prone to large subduction zone earthquakes, large basin-andrange earthquakes, and smaller, shallow, crustal earthquakes. Each of these different types of creates a different type of demand on a soil-bridge system. A subduction zone event, for instance, creates large magnitude, long-duration and long-period events that can damage long, flexible bridges. A shallow, crustal event, when it occurs near a bridge, can create an intense velocity pulse that can damage shorter, more brittle bridges. In addition to the challenges presented by considering multiple earthquake scenarios, the soil underlying bridge columns and abutments can significantly affect the seismic response of the overlying bridge superstructure. To truly examine the seismic performance of a bridge, one must consider soil-structure interaction. In this research we propose to create a finite element model of a typical PNW soil-bridge system within the program OpenSees. We will consider different soil conditions by using a series of complex, nonlinear Winkler springs. For this research, we will focus on large, subduction zone earthquakes, becasue this scenario is possibly the most damaging event in the PNW. However, for completeness, we will also examine shallow, crustal earthquakes as well as longer-return period basin-and-range earthquakes. The end-product of the reasearch will be guidance for how a typical bridge in varying soil conditions performs during differing, realistic earthquake motions. Future research will examine different bridge-foundation-soil models and earthquake motions. -- 2012-2013 Annual Report 11

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