Stability of Skewed I-shaped Girder Bridges Using Bent Plate Connections PDF Download
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Author: Craig Eugene Quadrato Publisher: ISBN: Category : Languages : en Pages : 572
Book Description
Lateral bracing systems consisting of cross frames and their connections play a significant role in the elastic buckling strength of steel girder bridges. By providing lateral and torsional stability, they prevent lateral torsional buckling of the girder during bridge construction prior to the concrete bridge deck curing. To perform this function, the bracing system must possess adequate strength and stiffness. And since each component of the bracing system acts in series, the overall stiffness of the system is less than the least stiff component. In skewed bridges, cross frames at the ends of the girders are installed parallel to the bridge skew angle, and their connection to the girder requires that the cross frames be at an angle that prohibits welding a stiffener from the cross frame directly to the girder web. To make this connection, many states use a bent plate to span the angle between the web stiffener and cross frame. While this bent plate connection is now being widely used, it has never been rationally designed to account for its strength or stiffness in the bracing system. Results from field studies show that the bent plate connection may be limiting the cross frame stiffness thereby hampering its ability to provide stability to the girder during construction. The result is significant girder end rotations. The purpose of this research is to classify the impact of the bent plate connection on the end cross frame stiffness in skewed straight steel girder bridges and propose methods to improve the end cross frame's structural efficiency. This research uses laboratory testing, finite element modeling, and parametric studies to recommend design guidance and construction practices related to the end cross frames of skewed steel girder bridges. In addition to recommending methods to stiffen the existing bent plate connection, an alternative pipe stiffener connection is evaluated. The pipe stiffener not only offers the possibility of a stiffer connection, but can also provide warping restraint to the end of the girder which may significantly increase the girder elastic buckling capacity.
Author: Craig Eugene Quadrato Publisher: ISBN: Category : Languages : en Pages : 572
Book Description
Lateral bracing systems consisting of cross frames and their connections play a significant role in the elastic buckling strength of steel girder bridges. By providing lateral and torsional stability, they prevent lateral torsional buckling of the girder during bridge construction prior to the concrete bridge deck curing. To perform this function, the bracing system must possess adequate strength and stiffness. And since each component of the bracing system acts in series, the overall stiffness of the system is less than the least stiff component. In skewed bridges, cross frames at the ends of the girders are installed parallel to the bridge skew angle, and their connection to the girder requires that the cross frames be at an angle that prohibits welding a stiffener from the cross frame directly to the girder web. To make this connection, many states use a bent plate to span the angle between the web stiffener and cross frame. While this bent plate connection is now being widely used, it has never been rationally designed to account for its strength or stiffness in the bracing system. Results from field studies show that the bent plate connection may be limiting the cross frame stiffness thereby hampering its ability to provide stability to the girder during construction. The result is significant girder end rotations. The purpose of this research is to classify the impact of the bent plate connection on the end cross frame stiffness in skewed straight steel girder bridges and propose methods to improve the end cross frame's structural efficiency. This research uses laboratory testing, finite element modeling, and parametric studies to recommend design guidance and construction practices related to the end cross frames of skewed steel girder bridges. In addition to recommending methods to stiffen the existing bent plate connection, an alternative pipe stiffener connection is evaluated. The pipe stiffener not only offers the possibility of a stiffer connection, but can also provide warping restraint to the end of the girder which may significantly increase the girder elastic buckling capacity.
Author: Anthony David Battistini Publisher: ISBN: Category : Languages : en Pages : 302
Book Description
Cross frames and diaphragms are essential to the stability of straight steel girder bridge systems as they help to resist lateral torsional buckling during construction and horizontal loading conditions. In skewed bridge systems, cross frames are often oriented parallel to the supports and hence, at an angle to the girder. To facilitate construction fit-up, plates, bent to match the skew angle, form the cross frame to stiffener connection. While the bent plate connection is a simple solution, it could introduce undesirable flexibility into the system, potentially compromising the effective brace stiffness. A proposed detail utilizing half pipe stiffeners may provide enhanced structural performance, while possibly reducing overall fabrication costs. Field and laboratory tests to determine the stiffness of both connection types are presented in the thesis.
Author: Federal Highway Federal Highway Administration Publisher: ISBN: Category : Languages : en Pages : 669
Book Description
This manual is intended to serve as a reference. It will provide technical information which will enable Manual users to perform the following activities:Describe typical erection practices for girder bridge superstructures and recognize critical construction stagesDiscuss typical practices for evaluating structural stability of girder bridge superstructures during early stages of erection and throughout bridge constructionExplain the basic concepts of stability and why it is important in bridge erection* Explain common techniques for performing advanced stability analysis along with their advantages and limitationsDescribe how differing construction sequences effect superstructure stabilityBe able to select appropriate loads, load combinations, and load factors for use in analyzing superstructure components during constructionBe able to analyze bridge members at various stages of erection* Develop erection plans that are safe and economical, and know what information is required and should be a part of those plansDescribe the differences between local, member and global (system) stability
Author: Mahendrakumar Madhavan Publisher: LAP Lambert Academic Publishing ISBN: 9783845404776 Category : Languages : en Pages : 476
Book Description
Curvature greatly complicates the behavior of horizontally curved steel plate girders used in bridge superstructures. The warping stress gradient across the width of I-girder flange plates reduces the vertical bending stress at which the flange plate buckles. The 2007 AASHTO Load and Resistance Factor Design Specifications eliminate the shortcomings of the 2003 AASHTO Guide Specifications for Horizontally Curved Bridges by unifying the flexural design of tangent and curved I-girder bridges. This book evaluates flange local buckling resistance based upon theoretical and analytical models that consider the effect of stress gradient across the flange coupled with the influence of rotational resistance provided by the web. The developed equations are verified using the finite element method, and the potential impact is demonstrated using the design example presented in the Guide Specifications.
Author: Paul Biju-Duval (Ph. D.) Publisher: ISBN: Category : Languages : en Pages : 470
Book Description
Because of its ability to be easily shaped, steel is an attractive material for curved girders. Plate girder and tub girder bridges, for example, are often the preferred solution for direct connectors in highway networks. This flexibility in fabrication, however, presents challenges for structural engineers because of the difficulties associated with accounting for combined bending and torsion with curved geometry. The potential presence of skewed supports is a further source of complexity. In fact, no commercial structural engineering program currently addresses the evaluation of plate girder and tub girder bridges while modeling them to the full extent of their three-dimensional configuration. Most engineers, for example, use a two-dimensional bridge representation, which is often accurate for typical design of a complete bridge but may also be unconservative in many cases. The few programs that allow a full three-dimensional representation require extensive knowledge of finite element theory as well as significant time to model any complex structure. This dissertation presents the assumptions, methodology and calculations involved in the programming of a new structural engineering program designed to assess the behavior and stability or curved plate girder and tub girder bridges during erection or deck placement. It then illustrates the capabilities of the program for various structural systems subjected to a variety of loads, from self-weight to wind and temperature loads. In addition to a linear elastic analysis, multiple types of analysis are offered to the engineer: a geometrically nonlinear analysis provides a more accurate behavior for flexible systems, a linearized buckling analysis yields an upper bound evaluation of the stability of the structure, while a modal dynamic analysis estimates the free vibration modes of that structure.
Author: James Zhou Publisher: ISBN: Category : Languages : en Pages : 20
Book Description
Lateral flange bending stresses can arise from a number of sources, such as wind loading or eccentric concrete placement, but of particular interest are lateral flange bending stresses, fl, that occur due to skew. Lateral flange bending stresses that occur in skewed bridge systems tend to develop due to lateral forces transferred through cross frames which may connect adjacent girders at different span points. In lieu of a refined analysis, the AASHTO (2010) LRFD Bridge Design Specifications currently permit engineers examining bridges skewed more than 20° to use a minimum value of fl = 10 ksi for an interior girder and fl = 7.5 ksi for an exterior girder. The estimates for fl provided within the AASHTO LRFD Bridge Design Specifications are based on a limited data set for skewed bridges. Additionally, since the AASHTO LRFD Bridge Design Specifications state that cross frames or diaphragms should be placed in a staggered configuration when a bridge is skewed more than 20°, the approximate values provided for fl should not be expected to be indicative of the lateral flange bending stresses experienced when cross frames are instead carried parallel to the skew in bridges skewed beyond 20°. The authors have performed a study to investigate the effects of cross frame orientation and skew angle upon lateral flange bending stresses, by examining lateral flange bending stresses in a suite of detailed 3D solid finite element analyses of skewed bridge systems, in which cross frame layout, spacing, and skew angle were varied. The findings of this study showed that cross frames placed parallel to the angle of skew produced significantly lower values for fl than cases in which cross frames were placed perpendicular to the girder line and staggered. Both reducing the skew angle and decreasing cross frame spacing were found to reduce lateral flange bending stresses. The values of lateral flange bending stress for all configurations were greater than the bounds of the approximate values suggested by AASHTO.
Author: Telmo Andres Sanchez Publisher: ISBN: Category : Bridges Languages : en Pages :
Book Description
The construction of horizontally curved bridges with skewed supports requires careful consideration. These types of bridges exhibit three-dimensional response characteristics that are not commonly seen in straight bridges with normal supports. As a result, engineers may face difficulties during the construction, when the components of the bridge do not fit together or the final geometry of the structure does not correspond to that intended by the designer. These complications can lead to problems that compromise the serviceability aspects of the bridge and in some cases, its structural integrity. : The three dimensional response that curved and skewed bridges exhibit is directly influenced by the bracing system used to configure the structure. In I-girder bridges, cross-frames are provided to integrate the structure, transforming the individual girders into a structural system that can support larger loads than when the girders work separately. In general, they facilitate the construction of the structure. However, they can also induce undesired collateral effects that can be a detriment to the performance of the system. These effects must be considered in the design of a curved and skewed bridge because, in some cases, they can modify substantially its response.
Author: American Association of State Highway and Transportation Officials. Subcommittee on Bridges and Structures Publisher: American Association of State Highway & Transportation Officials ISBN: Category : Technology & Engineering Languages : en Pages : 422
Author: Craig Eugene Quadrato
Author: Craig Eugene Quadrato
Author: Anthony David Battistini
Author: Federal Highway Federal Highway Administration
Author: Mahendrakumar Madhavan
Author: Paul Biju-Duval (Ph. D.)
Author: Mohamed Abdel-Azim Elewa
Author: Dann H. Hall
Author: James Zhou
Author: Telmo Andres Sanchez
Author: American Association of State Highway and Transportation Officials. Subcommittee on Bridges and Structures