Bridges And Structures

Impacts of Cascadia Subduction Zone M9 Earthquakes on Bridges in Washington State: Single-Degree-of-Freedom (SDOF) Idealized Bridges

The Cascadia Subduction Zone is capable of producing large-magnitude, megathrust earthquakes that will affect the performance of every new and existing bridge in the western half of Washington state. This project evaluated the impacts on bridges of a magnitude 9 (M9) earthquake to help agencies prioritize earthquake retrofit efforts and to support the development of emergency response plans.

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Investigation of Ultra-High Performance Concrete for Longitudinal Joints in Deck Bulb Tee Bridge Girders

Many state departments of transportation have used ultra-high performance concrete (UHPC) in bridge construction because of its advanced mechanical properties. In this study, researchers tested a new UHPC mix, developed at Washington State University, for its structural performance when used in a reinforced spliced connection between adjacent concrete deck bulb tee (DBT) bridge decks. Because DBT bridges can be constructed quickly, WSDOT is interested in using them on major highways. Use of UHPC could make DBT bridges more suitable for the heavier traffic loads on such roadways.

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Developing Extended Strands in Girder-Cap Beam Connections for Positive Moment Resistance

This project sought to increase the seismic safety of the state’s bridges by improving the connections among bridge components. A typical Washington state concrete bridge bent consists of cast-in-place piers, precast, pre-stressed girders, and a cap beam. Successful interaction among all three components must be achieved to transfer induced loads effectively and provide adequate resistance to seismic shaking. The cap beam comprises a precast crossbeam and a cast-in-place diaphragm, flush with the girders. To create the tension connection between the bottom girder flange and the cap beam, it is common to extend some of the bottom steel strands into the cast-in-place diaphragm, where they are anchored with strand vices and bearing plates. The goal of this project was to create a reliable, effective, and practically applicable way of anchoring strands extended from the girder into the cap beam.

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Development of Surface-Mounted Smart Piezoelectric Modules for Bridge Damage Identification and Safety Monitoring

The goal of this study was to develop viable tools that utilize ultrasonic smart piezoelectric material (lead zirconate titanate, PZT) to assess the condition of concrete bridges. Existing non-destructive testing methods for inspecting concrete structures all suffer from limitations in accuracy, cost, maneuverability, in situ capability, and implementation. The researchers determined that the surface-mounted PZT system tested was effective in determining the wave modulus of elasticity of concrete structures and is a promising alternative nondestructive technique for assessing concrete properties.

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Recycled Glass Fiber Reinforced Polymer Composites Incorporated in Mortar for Improved Mechanical Performance

In this study, recycled glass fiber reinforced polymer composites from end-of-life wind turbine blades were evaluated as a replacement for sand in cement mortar. In the last two decades, glass-based materials in the form of powder or fibers from recycled bottles and other products, and more recently recycled glass fiber reinforced polymer (GFRP) composites from end-of-life products or industrial waste, have been incorporated into cement-based mixtures in various proof-of-concept designs. To understand better how GFRP would affect the properties of mortar, researchers conducted a feasibility study to compare different GFRP sizes and percentages.

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Developing Connections for Longitudinal Joints between Deck Bulb Tees—Development of UHPC Mixes with Local Materials

In past decades, many state departments of transportation and the Federal Highway Administration have begun working with ultra-high performance concrete (UHPC), an advanced cementitious material. WSDOT has not used UHPC in highway bridge applications, such as connection joints for precast concrete decks and girders, because of the concrete’s high cost and because of general lack of experience with it. The goal of this project was to develop a UHPC mixture using materials available locally and domestically as an alternative to commercially available, pre-packaged UHPC products.

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Numerical Evaluation of Forces on Piled Bridge Foundations in Laterally Spreading Soil

For seismically active areas, designers must consider how bridge foundations will respond to ground liquefaction, particularly lateral spreading of the soil. Current design procedures generally rely on simplified analytical methods based on a two-dimensional description of the site geometry. However, numerous bridges affected by lateral spreading during past earthquakes have displayed three-dimensional soil deformation that cannot be captured in a two-dimensional analysis, and an analysis that assumes 2-D conditions may be overly conservative, leading to unnecessarily expensive design solutions. The objectives of this research were to identify and quantify the mechanisms that may result in potential reductions in the bridge foundation demands that develop during lateral spreading by considering the 3-D geometry of the bridge site.

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Liquefaction-Induced Downdrag on Drilled Shafts

This study developed an analytical method that can account for the liquefaction-caused settlement of deep foundations, in particular a structure’s drilled shafts. During and following liquefaction caused by an earthquake, sandy soil layers shrink in volume and settle. Depending on the site conditions, the changes in forces that result from liquefaction-induced soil settlement and downdrag can significantly affect the performance of drilled shafts, even damaging the structure. The new analytical method, based on the neutral plane method, proved successful in application to a case study of downdrag observed during the February 2010 8.8-magnitude earthquake in Maule, Chile.

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Shear Design Expressions for Concrete-Filled Steel Tubes and Reinforced Concrete-Filled Tube Components

Concrete-filled steel tubes (CFSTs) and reinforced concrete-filled steel tubes (RCFSTs) are increasingly used in transportation structures as piers, piles, caissons, or other foundation components. CFSTs combine steel and concrete to create efficient and economical composite structural members. Because currently accepted methods for calculating the shear capacity of CFSTs and RCFTs are adapted from shear strength equations used for structural steel or reinforced concrete components, they likely significantly underestimate the shear capacity of the composite section, potentially increasing undesirable conservatism and cost. This research used integrated experimental testing methods, combined with high-resolution analytical models, to investigate the shear capacity of CFST and RCFST members and to develop an improved and more accurate shear strength expression. The resulting new expression provides a total CFST shear strength of 2 times that produced by WSDOT’s currently used expression and is proposed for implementation in WSDOT’s Bridge Design Manual.

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