Washington State, Washington, United States
Washington State, Washington, United States

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Tobias D.H.,University of Illinois at Springfield | Bardow A.K.,0 Park Plaza | Dekelbab W.,Transportation Research Board | Kapur J.,Bridge and Structures Office | And 4 more authors.
Practice Periodical on Structural Design and Construction | Year: 2014

Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal. © 2014 American Society of Civil Engineers.

Khaleghi B.,Bridge and Structures Office
Transportation Research Record | Year: 2010

The need for accelerated bridge construction (ABC) arises from the increases in traffic congestion over the past few decades and the corresponding costs and safety issues manifest in many forms, including exposure of workers to traffic hazards and waste of time caused by delays. Prefabricated bridge components are in increasing demand for ABC. Precasting eliminates the need to form, cast, and cure concrete in the work zones, making bridge construction safer and improving quality and durability. Precast bridges consisting of pretensioned girders, post- tensioned spliced girders, trapezoidal open-box girders, and other types of superstructure members are often used for ABC; however, bridge engineers are concerned about the durability and performance of bridges made of precast members in areas of high and moderate seismicity. Starting in 2008, the Washington State Department of Transportation (DOT) initiated a practice development and implementation for ABC. Washington State DOT has established a task force headed by an ABC advisory committee to develop standards, guidelines, and key policies for implementing structure design for ABC.

Arab A.,George Washington University | Badie S.S.,George Washington University | Manzari M.T.,George Washington University | Khaleghi B.,Bridge and Structures Office | And 2 more authors.
PCI Journal | Year: 2014

End zone cracking of pretensioned concrete girders has been become more prevalent due to the increased use of high-strength concrete, deep girders, thin webs, and high prestress forces. This paper provides a methodology for analytically simulating the behavior of pretensioned concrete members. The finite element method approach developed in this study was used to investigate the behavior of the end zone reinforcement of the 210 ft (64 m) long, 100 in. (2500 mm) deep super girders used in construction of the Alaskan Way Viaduct replacement in Seattle, Wash. End zone reinforcement of eight girders was instrumented for this purpose. The finite element analysis accurately predicted the measurements collected from the instrumented girders. The results of the finite element are compared with those of several other methods.

Walkenhauer B.J.,Coughlin Porter Lundeen Inc. | McLean D.I.,Washington State University | Boone C.,Bridge and Structures Office | Lamont M.,T. Y. Lin International
Transportation Research Record | Year: 2011

This study investigated retrofit measures for improving the seismic performance of cruciform-shaped columns in the Aurora Avenue Bridge in Seattle, Washington. Tests on column specimens representing as-built conditions resulted in shear failures at modest displacement levels, accompanied by severe strength and stiffness degradation. Tests on column specimens retrofitted with jacketing of fiber-reinforced polymer (FRP) resulted in improved performance compared with that obtained for the as-built column specimens. The FRP jacket needed to be anchored in the reentrant corners of the cruciform-shaped columns to be effective. In addition, the FRP jacket did not provide adequate confinement to prevent flexural hinge degradation. The final retrofit design that incorporated reentrant corner anchorage and grout-filled steel collars at the plastic hinge regions produced a ductile flexural response.

Brice R.,Bridge and Structures Office | Khaleghi B.,Bridge and Structures Office
PCI Journal | Year: 2010

Minimum flexural reinforcement requirements have been a source of controversy for many years. The purpose of such provisions is to encourage ductile behavior in flexural members by providing a reasonable margin of safety between first cracking and flexural failure or, alternatively, a reasonable amount of overstrength beyond the applied factored loads. The " primary objectives of this study were to summarize the apparent origin of current minimum reinforcement provisions, examine the margin of safety provided by existing provisions for reinforced concrete members of different sizes and shapes, and propose new requirements when they provide more-consistent results than those from existing provisions. Five existing or proposed methods were included in the study. Parametric analyses show that the proposed method provides the most reasonable margins of safety among the methods examined. The study focuses on determinate reinforced concrete beams, which include only mild tensile reinforcement and no prestressing. High-strength steel and concrete were included. The study also found that, in many cases, flexural failure at minimum reinforcement levels can be initiated by crushing of the concrete rather than the fracture of the reinforcing steel.

Yang M.,University of Texas at San Antonio | Qiao P.,Washington State University | McLean D.I.,Washington State University | Khaleghi B.,Bridge and Structures Office
PCI Journal | Year: 2010

This paper studies the capacity of prestressed concrete bridge girders to withstand overheight truck impacts. The numerical model of the bridge was validated with the existing experimental data in the literature. The elastic-plastic modeling of concrete damage and quasistatic impact simulation of the bridge were considered. Parametric studies were then conducted with respect to the spacing and depth of intermediate diaphragms as well as girder types from which the role of intermediate diaphragms in protection and enhancement of prestressed concrete bridge girders from truck impacts is obtained. From the simulation results, it was concluded that the optimum spacing of intermediate diaphragms (that is, 25.0 ft [7.62 m]) is consistent with the results reported for previous studies. The depth of intermediate diaphragms should be extended to the top edge of the bottom flange of girders to provide maximum impact protection. Wide flanges in girders increase the bending stiffness and reduce the horizontal deflection and correspondingly decrease damage areas. However, deep webs in girders introduce a large rotation with respect to the deck, and thus increase the deflection under the truck impact. Design guidelines for typical parameters for intermediate diaphragms in prestressed concrete bridges are provided. The numerical finite-element parametric study provides a better understanding of placement and size of intermediate diaphragms in prestressed concrete bridges and their role in protecting girders from overheight truck impacts.

Loading Bridge and Structures Office collaborators
Loading Bridge and Structures Office collaborators