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31 results on '"Khaleghi, Bijan"'

5. Strength from within

Author

Khaleghi, Bijan and Schueler, JoAnn

Subjects
Tunneling -- Design and construction, Rock slopes, Reinforced concrete -- Usage, Rock mechanics -- Research, Business, Engineering and manufacturing industries, Science and technology
Abstract

The rehabilitation of the Knapps Hill Tunnel of Washington state is discussed. Innovative methods are used to stabilize the rock slopes with rock bolts and a layer of shortcrete. The tunnel strengthening is done by a layer of shortcrete applied to the tunnel's interior.

Published
2002

24. Roads and Bridges

Author

Singh, Mahendra P., primary, Khaleghi, Bijan, additional, Saraf, Vijay K., additional, Jain, Sudhir K., additional, Norris, Gary, additional, Goel, Rajiv, additional, and Murty, C. V. R., additional

Published
2002
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27. Effects of overheight truck impacts on intermediate diaphragms in prestressed concrete bridge girders.

Author

Mijia Yang, Pizhong Qiao, McLean, David I., and Khaleghi, Bijan

Subjects
PRESTRESSED concrete bridges, GIRDER testing, TRUCKS, DIAPHRAGMS (Structural engineering), IMPACT (Mechanics), BRIDGE design & construction
Abstract

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. [ABSTRACT FROM AUTHOR]

Published
2010
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28. Bent on safety.

Author

Stanton, John, Eberhard, Marc, Marsh, Lee, Khaleghi, Bijan, Haraldsson, Olafur, Janes, Todd, Tran, Hung Viet, and Davis, Phillip

Subjects
BRIDGE design & construction, CONCRETE
Abstract

The article discusses the bridge bent concept developed by a multidisciplinary team made up of personnel from the Universityof Washington, the Washington State Department of Transportation (WSDOT) and BergerABAM Engineers for accelerated bridge construction (ABC). The system permits the rapid erection of a bent so girders can start to be set in the shortest time possible. Excavation of the footing is first, followed by the casting of a temporary concrete pad in its center, if needed.

Published
2012

29. Authors' response.

Author

Brice, Richard, Seguirant, Stephen J., and Khaleghi, Bijan

Subjects
GIRDERS, PRESTRESSED concrete bridges
Abstract

A response from the author of the article "Evaluation of Common Design Policies for Precast, Prestressed Concrete I Girder Bridges," by Richard Brice in the Fall 2013 issue is presented.

Published
2014

30. Simplified Method for Shear Design of Prestressed Concrete Girders

Author

Lwin, M. and Khaleghi, Bijan

Abstract

The new AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications incorporate the modified compression field theory for shear design of prestressed and non-prestressed concrete members. This method is based on the variable-angle truss analogy model and takes into account the inclination of diagonal shear cracks, the strain in longitudinal steel, and the applied shear stress on a section. This is a realistic approach to predict the shear resistance of any section of a concrete member. However, for prestressed concrete sections, an iterative process is required in conjunction with charts and tables to determine the shear resistance of the sections. The process is cumbersome and time consuming. In an effort to simplify the process, Washington State Department of Transportation has completed a parametric study that results in a simplified method of using fixed shear design parameters. The simplified method saves significant time in shear design of prestressed girders, especially when it is used to standardize the shear reinforcement in a series of standard prestressed concrete girders.

Published
1999
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31. Inelastic stability of tapered, singly-symmetric beam-columns.

Author

Khaleghi, Bijan,

Subjects
Engineering, Civil.
Abstract

The purpose of this study is to determine the inelastic lateraltorsional buckling load of a linearly web-tapered member having unequal flanges and subjected to unequal end moments and axial load. Triangular residual stress patterns in flanges and uniform tensile stress across the web are assumed to exist. The total potential energy functional for such a member is developed and the inelastic effects are included. Using the standard techniques of calculus of variations, the three differential equations describing the behavior of the member are derived and the natural and force boundary conditions are determined. Two of these equations, which are coupled, describe the out-of-plane behavior of the member. Central difference expressions are used to transform these two equations into difference equations. In order to determine the yield pattern at each station along the member, a new method based on the solution of the equations of equilibrium is proposed. By solving these two simultaneous, nonlinear equations, the yield parameters are computed. The section properties of the partially yielded cross-sections are computed using the yield parameters. The section properties are used to satisfy the difference equations at different nodes along the member. The value of the determinant of these equations is tested for different trial values of the buckling load until a zero value is found which insures buckling. The buckling mode shape is then obtained by assuming one of the displacements equal to unity, cancelling one equation and solving the rest of the equations using Gauss-Jordan elimination method.

Published
1982

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