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Bridges And Structures

Safety of Long Girders during Handling and Transportation: Lateral Stability and Cracking

Today’s girders are much longer and heavier than those that have been used in the past. This poses challenges to transportation agencies in handling, transporting, and erecting the girders, as under their own weight they can buckle laterally and fail.  Traditionally, analysis of this potential behavior has ignored torsional deformations because doing so greatly simplifies the calculations. However, although traditional models have so far proved adequate, today’s longer, heavier girders are challenging their assumptions. And with those girders, the potential consequences of ignoring torsional deformation could prove to be not only costly in terms of time and money but also unsafe. This project is seeking to improve the fundamental characterization of girder instability by developing new models that include torsional deformation and consider a broad range of material properties and concrete weights. Models will be developed to analyze both the lateral stability of uncracked girders and the role of cracking in reducing girder stiffness and thus increasing instability. The researchers will assist WSDOT in implementing the findings by providing the lateral stability criteria necessary to develop a set of new girder shapes that will take advantage of the materials that allow the use of longer spans.

Principal Investigators:
John Stanton, Civil and Environmental Engineering, UW
Richard Wiebe, Civil and Environmental Engineering, UW

Sponsor: WSDOT
WSDOT Technical Monitor: Bijan Khaleghi
WSDOT Project Manager: Mustafa Mohamedali
Scheduled completion: January 2024

Data-Driven Assessment of Post-Earthquake Bridge Functionality and Regional Mobility

The performance of bridges in an earthquake is critical to the mobility of nearly all transportation modes after the event. Damage to bridges near critical facilities, such as airports and ports, can also limit the contributions of those facilities to the post-event mobility of people and freight. Consequently, local, state, and federal engineers and emergency managers need reliable estimates of post-event bridge functionality so that they can plan pre-event mitigation, post-event response and mobility, and long-term recovery. The goal of this project is to predict the post-earthquake functionality of the approximately 10,000 bridges in Oregon and Washington following a Cascadia Subduction Zone (CSZ) magnitude-9.0 earthquake. The project will also evaluate the likelihood that crucial highway lifeline corridors will be available to support post-earthquake mobility. Key results from this project will include a database of bridge performance metrics for 100,000 simulated cases of bridge and intensity measures, and maps that show probable bridge functionality and re-opening times following CSZ earthquakes. These maps will enable WSDOT and ODOT to plan and make informed decisions about post-earthquake emergency routes.

Principal Investigators:
Christopher Motter, Civil and Environmental Engineering, WSU
Adam Phillips, Civil and Environmental Engineering, WSU
Marc Eberhard, Civil and Environmental Engineering, UW
Jeffrey Berman, Civil and Environmental Engineering, UW
Brett Maurer, Civil and Environmental Engineering, UW

Sponsor: PacTrans
Scheduled completion: August 2022

Performance of Steel Jacket Retrofitted Reinforced Concrete Bridge Columns in Cascadia Subduction Zone Earthquakes

In 1991 WSDOT began a seismic retrofit program for state bridges that continues today. WSDOT’s primary method for retrofitting concrete bridge columns is steel jackets. The USGS recently released updated hazard maps that require structural design in Western Washington to plan for increased levels of seismicity, reflecting the potential for the Cascadia Subduction Zone (CSZ) to generate large magnitude, long duration earthquakes. The ability of WSDOT’s bridge columns retrofitted with steel jackets to resist this increased earthquake hazard level is not well understood, and questions remain regarding the level of damage that would be sustained in a CSZ earthquake. If the level of retrofit is not sufficient to prevent collapse, the millions of dollars expended by WSDOT on retrofit will not deliver the intended results. This project will characterize the expected performance, ductility capacity, and collapse probability of steel jacket retrofitted bridge columns in CSZ earthquakes and will develop a simple tool that WSDOT can use to assess whether a standard steel jacket retrofit is adequate to resist a design level earthquake for each bridge column in its inventory.

Project Investigators:
Christopher Motter, Civil and Environmental Engineering, WSU
Adam Phillips, Civil and Environmental Engineering, WSU

Sponsor: WSDOT
WSDOT Technical Monitor: Bijan Khaleghi
WSDOT Project Manager: Mustafa Mohamedali
Scheduled completion:  September 2021

Seismic Retrofit of Hollow Piles

The overall goal of the proposed research is to design, and prove experimentally, methods to seismically retrofit prestressed concrete hollow pile-columns used in bridges.  WSDOT maintains approximately 25 bridges that are supported on hollow precast, prestressed concrete pile-columns. Most were constructed in the 1960s. The seismic performance of these bridges is in now question because the hollow sections have been shown to have little flexural ductility, which may cause them to fail prematurely. This project will determine the flexural strength and deformation capacity of a typical as-built, hollow, precast, pre-tensioned pile-column before retrofitting. Researchers will then develop a retrofit method, including design procedures, for the potential plastic hinge at the cap beam connection, and they will develop implementation procedures for the retrofit method. In addition, this project will create a simple numerical modeling tool that will allow WSDOT to rank existing bridges according to the risk that they pose to help it prioritize bridge retrofitting.

Principal Investigators:
John Stanton, Civil and Environmental Engineering, UW
Paolo Calvi, Civil and Environmental Engineering, UW

Sponsor: WSDOT
WSDOT Technical Monitor: Bijan Khaleghi
WSDOT Project Manager: Doug Brodin
Scheduled completion: December 2019

Update for Steel Bridges

The last official release of a steel version of the bridge rating software that WSDOT uses was Bridg97. That software offers WSDOT’s and FHWA’s standard rating systems, both based on Load Factor Rating (LFR). Unfortunately, it depends on software packages that have become obsolete. WSDOT has also adapted a concrete version of Bridg (last official release was Bridg10), whose updated interface is platform independent.  Steel Bridg shares large portions of the user interface with concrete Bridg, and so parallel development has been dedicated to porting the steel-­specific user interface into a new, platform-independent steel Bridg version, although it still has technical limitations related to WSDOT and FHWA standard rating, as well as graphics capabilities. This project is working to further upgrade the new steel Bridg by porting the load module and LRFR-specific extensions from the concrete Bridg to the improved steel Bridg software and otherwise utilizing the existing features of Bridg97.

Principal Investigator: Peter Mackenzie-Helnwein, Civil and Environmental Engineering, UW
Sponsor: WSDOT
WSDOT Technical Monitor: Mohamad Al-Salman
WSDOT Project Manager: Jon Peterson
Scheduled completion: December 2023

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