Download or read book Skewed Steel Bridges Part II written by James Zhou and published by . This book was released on 2017 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: Skewed bridges in Kansas are often designed such that the cross-frames are carried parallel to the skew angle up to 40°, while many other states place cross-frames perpendicular to the girder for skew angles greater than 20°. Skewed-parallel cross-frames are longer and may require different connections than cross-frames oriented perpendicular to the girder. Therefore, it is important to determine whether the cross-frames and their corresponding connecting elements placed in a parallel-to-skew configuration are sufficiently designed to resist lateral torsional buckling demands using current KDOT practices. The authors have performed a study to investigate the effect of cross-frame orientation, skew angle, and cross-frame connection upon bridge system behavior and cross-frame stresses. In a suite of detailed 3D, solid finite element analyses models of skewed bridge systems, cross-frame layout, connection thickness and type, and skew angle were varied. Skewed bridge systems with cross-frames placed parallel to the skew angle as well as systems with cross-frames arranged in a staggered configuration were considered. Varying bent plate connection thicknesses and a half-pipe connection were also analyzed. Cross-frame spacing of 4.6 m [15 ft] and 9.14 m [30 ft] were examined; severe cross-frame spacing of 13.7 m [45 ft] was also considered to examine behavior at very long unbraced lengths. The findings of this study showed that skew angle, skew configuration, and connection type all influenced the strength and stiffness of system. The data showed that cross-frame placed parallel to skew up to an angle of 40° performed similar or better than cross-frames oriented perpendicular to skew for every given skew angle and connection type.

Download or read book Cross frame Connection Details for Skewed Steel Bridges written by Craig Quadrato and published by . This book was released on 2010 with total page 393 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Skewed Steel Bridges written by James Zhou and published by . This book was released on 2016 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Guidelines for Analysis Methods and Construction Engineering of Curved and Skewed Steel Girder Bridges written by and published by Transportation Research Board. This book was released on 2012 with total page 199 pages. Available in PDF, EPUB and Kindle. Book excerpt: "TRB's National Cooperative Highway Research Program (NCHRP) Report 725: Guidelines for Analysis Methods and Construction Engineering of Curved and Skewed Steel Girder Bridges offers guidance on the appropriate level of analysis needed to determine the constructability and constructed geometry of curved and skewed steel girder bridges. When appropriate in lieu of a 3D analysis, the guidelines also introduce improvements to 1D and 2D analyses that require little additional computational costs."--Publication information.

Download or read book Cross frame and Diaphragm Behavior for Steel Bridges with Skewed Supports written by Todd Aaron Helwig and published by . This book was released on 2003 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Stability of Skewed I shaped Girder Bridges Using Bent Plate Connections written by Craig Eugene Quadrato and published by . This book was released on 2010 with total page 572 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Skewed Cross Frame Connection Stiffness written by Anthony David Battistini and published by . This book was released on 2009 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Skewed Steel Bridge Cross frame Response to Truck Loading written by Shane David Murphy and published by . This book was released on 2012 with total page 241 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Cross frame Forces in a Straight Bridge with Normal Supports written by Matthew Eric Moore and published by . This book was released on 2018 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cross-frame and diaphragm systems are important structural elements in steel I-girder bridges. These members enhance the lateral-torsional buckling resistance in straight girder systems by reducing the unbraced length. The critical stage for the braces from a stability perspective often occurs during construction of the concrete bridge deck when the non-composite steel girders must resist the entire construction load. The braces not only enhance the lateral-torsional buckling resistance of the girders, but are also necessary to resist the torsion applied to the girders due to the deck overhang construction, and distribute lateral loads across the structure from sources such as wind. In horizontally curved bridges, the braces are primary structural elements in the superstructure and engage the girders across the width of the bridge to behave as a structural system to resist the torsion that develops as a result of the curved geometry. For straight girder systems, the specifications of the American Association of State Highway and Transportation Officials (AASHTO) have generally provided little guidance in the sizing of the braces other than recommended connection plate (web stiffener) details or slenderness limits. While there have been many advances in recent years towards improving the understanding of the behavior of cross-frame systems, there has not been sufficient research carried out on the proper loading conditions for assessing the fatigue performance of cross-frames. The work outlined in this thesis is part of a larger study on the behavior of cross-frames in steel bridge system. The study is funded by the National Cooperative Highway Research Program (NCHRP 12-113). The fundamental goals of the research investigation are to produce methodologies and design guidelines for the following: evaluation of fatigue design stresses in cross-frames in straight and horizontally curved steel I-girder bridges; calculation of minimum cross-frame strength and stiffness requirements for stability bracing of I-girders during construction and in-service; development of improved methods to account for the influence of end connection details on cross-frame stiffness that extend beyond and improve upon the suggested guidance currently provided in Article C4.6.3.3.4 of the AASHTO LRFD Bridge Design Specifications. This work includes field monitoring and parametric FEA studies. The field studies are focused on three bridges: 1) a straight bridge with normal supports, 2) a straight bridge with skewed supports, and 3) a horizontally curved bridge. The field studies include rainflow monitoring of fatigue induced stresses in select cross-frames and the girders for a period of approximately 1 month as well as live load tests using trucks of known weights. This thesis focuses on some of the background studies, a survey of bridge owners around the United States, as well as the instrumentation and live load tests on the straight bridge with normal supports

Download or read book Influence of Cross frame Detailing on Curved and Skewed Steel I girder Bridges written by Cagri Ozgur and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Curved and skewed I-girder bridges exhibit torsional displacements of the individual girders and of the overall bridge cross-section under dead loads. As a result, the girder webs can be plumb in only one configuration. If the structure is built such that the webs are plumb in the ideal no-load position, they generally cannot be plumb under the action of the structure's steel or total dead load; hence, twisting of the girders is unavoidable under dead loads. The deflected geometry resulting from these torsional displacements can impact the fit-up of the members, the erection requirements (crane positions and capacities, the number of temporary supports, tie down requirements, etc.), the bearing cost and type, and the overall strength of the structure. Furthermore, significant layover may be visually objectionable, particularly at piers and abutments. : If the torsional deflections are large enough, then the cross-frames are typically detailed to compensate for them, either partially or fully. As specified in Article C6.7.2 of the AASHTO LRFD Specifications, different types of cross-frame detailing methods are used to achieve theoretically plumb webs under the no-load, steel dead load, or total dead load conditions. Each of the cross-frame detailing methods has ramifications on the behavior and constructability of a bridge. Currently, there is much confusion and divergence of opinion in the bridge industry regarding the stage at which steel I girder webs should be ideally plumb and the consequences of out-of-plumbness at other stages. Furthermore, concerns are often raised about potential fit-up problems during steel erection as well as the control of the final deck geometry (e.g., cross-slopes and joint alignment). These influences and ramifications of cross-frame detailing need to be investigated and explained so that resulting field problems leading to needless construction delays and legal claims can be avoided.

Download or read book Cross frame and Diaphragm Behavior for Steel Bridges with Skewed Supports written by Liqun Wang and published by . This book was released on 2002 with total page 590 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigation of the Performance of a Skewed Steel Bridge with and Without Cross frames written by Asmaa Taha Ibrahim Abo Alouk and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In addition to this test, another test was previously conducted for the same bridge with the presence of the intermediate cross-frame, which gave an opportunity to compare the bridge's performance with and without cross-frames. The difference in the distribution factor between the bridge with the cross-frame and the bridge without them was less than or equal to 5%, according to the results of the comparison. Field data shows that the bridge with the cross-frames is subjected to higher lateral and warping stresses than the bridge without them. In addition to the field tests, a finite element analysis (FEA) was conducted, and compared to the field data. The FEA predictions closely match the field data. In addition, The FEA showed that at the inelastic load level, the cross-frames did not contribute to redistributing the load, as these cross-frames yielded much earlier than the heavily loaded girder. Finally, a unique finding in this study was that cross-frames induce concentrated major-axis bending moments that change the bridge's expected behavior.

Download or read book Improved Design Specifications for Horizontally Curved Steel Girder Highway Bridges written by Dann H. Hall and published by Transportation Research Board. This book was released on 1999 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Spatial Interaction Between Cross Frames and Girders of Multi stringer Skewed Steel Bridges written by Wassef E. Elmir and published by . This book was released on 1988 with total page 502 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Cross frame Bracing of Steel Trapezoidal Box Girder Bridges with Skewed Supports written by Duane Milligan and published by . This book was released on 2002 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Instrumentation and Live Load Testing of I girder Bridges for Cross frame Fatigue Analysis written by Esteban Zecchin and published by . This book was released on 2019 with total page 654 pages. Available in PDF, EPUB and Kindle. Book excerpt: The work outlined in this thesis is part of a larger study on the behavior of cross-frames in steel bridge systems. The study is funded by the National Cooperative Highway Research Program (NCHRP 12-113). The fundamental goals of the research investigation are to produce methodologies and design guidelines for the following: • evaluation of fatigue design stresses in cross-frames in straight and horizontally curved steel I-girder bridges; • calculation of minimum cross-frame strength and stiffness requirements for stability bracing of I-girders during construction and in-service; • development of improved methods to account for the influence of end connection details on cross-frame stiffness that extend beyond and improve upon the suggested guidance currently provided in Article C4.6.3.3.4 of the AASHTO LRFD Bridge Design Specifications. This work includes field monitoring and parametric FEA studies. The field studies are focused on three bridges: 1) a straight bridge with normal supports, 2) a straight bridge with skewed supports, and 3) a horizontally curved bridge. The field studies include rainflow monitoring of fatigue induced stresses in select cross-frames and the girders for a period of approximately 4 weeks as well as live load tests using trucks of known weights. This thesis focuses on the instrumentation and live load tests performed in the three bridges. In addition to the field data, an assessment of the most widely used commercial design software for steel bridges was carried out. The software was selected based upon a survey of several bridge owners and designers

Download or read book Stiffness and Fatigue Behavior of Cross Frames for Steel Bridge Applications written by Anthony David Battistini and published by . This book was released on 2014 with total page 760 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cross frames are critical for the stability of straight and curved steel bridges. Conventional cross frames are often fabricated from steel angles which are welded to gusset plates through one leg only. Due to this eccentric connection, these angles have substantial bending at the connection that can reduce the member stiffness and can potentially decrease fatigue performance. Because of the low buckling strength, cross frames with angle diagonals are often designed as tension-only systems, therefore increasing the necessary steel to be an effective brace. Improved behavior may result if concentric members are utilized. The increased buckling strength of tubes and double angles results in effective members in both compression and tension, and a single diagonal cross frame can provide effective bracing; however, a suitable connection must be developed. Tubes are often connected by slotting the tube in the center and welding to a gusset plate, which requires precise fabrication. Two proposed solutions that would connect easily to the ends of the member and seal the end of the tube include a steel casting and a T-stem connection. The dissertation studies the development of a steel casting for use in cross frame design and evaluates the performance of the various details described herein in regards to stiffness, strength, and fatigue. Additionally, the dissertation covers the behavior of single angle X and K frame configurations. To date, the determination of the single angle fatigue detail has been largely based on component tests only. The project incorporated full-scale cross frame fatigue tests to fully examine the interaction of the cross frame members with the overall structure. Results from currently used details and proposed connections provide insight to the live load behavior of these braces and multiple recommendations are made to improve the fatigue life. The project examined the stiffness behavior of current and proposed cross frame layouts with large-scale laboratory tests and computational modeling. From these results, a case study compares the fatigue analysis of a commercial structural software package to the stress ranges obtained in a three-dimensional finite element model. Suggestions on how to properly model the cross frames are given.