Experimental and Analytical Evaluation of Cross-frame Fatigue Behavior in Steel I-girder Bridges PDF Download
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Author: Matthew Craig Reichenbach Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Cross-frames are important structural components that serve many functions throughout the service life of steel I-girder bridge systems. They primarily act as stability braces to enhance the lateral-torsional buckling resistance of the girders during erection and deck construction, but also distribute live loads in the final composite condition. Under repetitive load cycles caused by heavy truck passages, cross-frames and their connections are susceptible to load-induced fatigue cracking if not properly designed. Cross-frames have historically been detailed and fabricated based on general rules-of-thumb and experience. In recent years, however, developments in bridge design specifications have necessitated the modernization of cross-frame design and analysis practices. Cross-frames are now designed and detailed based on rational analysis for all stages of construction and service life, which has further emphasized the importance of accurate and reliable analysis techniques and design criteria. Although considerable research over the past several decades has improved cross-frame design and analysis, the design industry has generally lacked quantitively based guidance on load-induced behavior of cross-frames in composite, in-service bridges. As such, this dissertation explores two major concepts: (i) the influence of skewed and curved superstructure geometry on the fatigue response of cross-frames and (ii) the limitations of simplified analysis techniques commonly utilized in commercial software programs with respect to estimating cross-frame force effects. Field experiments were performed on three steel I-girder bridges in the greater Houston area, and the stress ranges induced in key cross-frame members from truck traffic were monitored for one month each. Upon validating a finite-element approach with the measured data, an extensive analytical parametric study was conducted to expand the breadth and depth of knowledge gained from the limited field studies. In general, the load-induced fatigue behavior of conventional X- and K-type cross-frames were examined for a variety of bridge geometries commonly found in the United States. These analyses were performed with different levels of computational refinement, ranging from sophisticated three-dimensional approaches to simplified two-dimensional approaches. Based on the data collected and processed from the experimental and analytical studies, recommendations are proposed to improve the design and analysis of cross-frames in composite bridge structures. Because cross-frames represent a costly component of fabrication and erection, these recommendations ultimately lead to improved efficiency and economy of new steel bridge construction
Author: Matthew Craig Reichenbach Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Cross-frames are important structural components that serve many functions throughout the service life of steel I-girder bridge systems. They primarily act as stability braces to enhance the lateral-torsional buckling resistance of the girders during erection and deck construction, but also distribute live loads in the final composite condition. Under repetitive load cycles caused by heavy truck passages, cross-frames and their connections are susceptible to load-induced fatigue cracking if not properly designed. Cross-frames have historically been detailed and fabricated based on general rules-of-thumb and experience. In recent years, however, developments in bridge design specifications have necessitated the modernization of cross-frame design and analysis practices. Cross-frames are now designed and detailed based on rational analysis for all stages of construction and service life, which has further emphasized the importance of accurate and reliable analysis techniques and design criteria. Although considerable research over the past several decades has improved cross-frame design and analysis, the design industry has generally lacked quantitively based guidance on load-induced behavior of cross-frames in composite, in-service bridges. As such, this dissertation explores two major concepts: (i) the influence of skewed and curved superstructure geometry on the fatigue response of cross-frames and (ii) the limitations of simplified analysis techniques commonly utilized in commercial software programs with respect to estimating cross-frame force effects. Field experiments were performed on three steel I-girder bridges in the greater Houston area, and the stress ranges induced in key cross-frame members from truck traffic were monitored for one month each. Upon validating a finite-element approach with the measured data, an extensive analytical parametric study was conducted to expand the breadth and depth of knowledge gained from the limited field studies. In general, the load-induced fatigue behavior of conventional X- and K-type cross-frames were examined for a variety of bridge geometries commonly found in the United States. These analyses were performed with different levels of computational refinement, ranging from sophisticated three-dimensional approaches to simplified two-dimensional approaches. Based on the data collected and processed from the experimental and analytical studies, recommendations are proposed to improve the design and analysis of cross-frames in composite bridge structures. Because cross-frames represent a costly component of fabrication and erection, these recommendations ultimately lead to improved efficiency and economy of new steel bridge construction
Author: Joshua Benjamin White Publisher: ISBN: Category : Languages : en Pages : 560
Book Description
There have been a number of advances in the level of understanding of cross-frame systems for steel I-girder bridges; however, very little work has focused on the proper loading conditions to produce an adequate estimate of the fatigue load in cross-frames. The goal of this research is to provide an improved definition of the fatigue loading for cross-frames in straight, horizontally-curved, and skewed steel I-girder bridges which will be analyzed using refined analysis techniques. In order to compare load effects, three bridges were instrumented and monitored. The bridges include: i) a straight bridge with normal supports, ii) a straight bridge with skewed supports, and iii) a horizontally curved bridge with radial supports. Data gathered from the field instrumentation was used to validate three-dimensional finite element analysis (FEA) models that were used to carry out extensive parametric analyses to improve the understanding of the behavior of cross-frame stresses as a function of truck position on the bridge. A wide range of geometrical parameters of straight and horizontally curved bridges were used to understand the general behavior of the bridges. The primary objectives of this research include the following: 1) Investigate the adequacy of the current AASHTO (American Association of State Highway and Transportation Officials) fatigue load model for the design of cross frames in steel I-girder bridges. 2) Investigate the effects of multiple presence on the design of cross-frames in steel I-girder bridges. 3) Investigate the reliability of the developed load model and identify the gaps in knowledge of cross-frame detail resistance data as it relates to the reliability of current design practices. These objectives were accomplished by examining recently collected, high-resolution, multi-lane weigh-in-motion (WIM) data, which represent actual truck traffic records in the US. The current AASHTO fatigue design load model was evaluated by comparing cross-frame load effects caused by the fatigue load model to load effects caused by simulated truck traffic representing actual live load. Influence surfaces generated from three-dimensional FEA models provided information on the stresses in select cross-frame members as a function on truck position on the bridge deck. WIM data representing real truck traffic (tens of millions of truck records) were filtered and analyzed; multi-lane data were analyzed using a cluster analysis. The statistical parameters of this WIM study were used to simulate actual live load on the three-dimensional bridge models and compare load effects to those generated by a fatigue design truck. The outcome of this study indicates the current fatigue design truck axle and weight configuration and placement of the fatigue design truck to maximize design-controlling fatigue effects for both the Fatigue I and Fatigue II AASHTO limit states is overly conservative. Stochastic techniques were used to investigate the implications of new load factors in the context of reliability-based fatigue design
Author: Steffen P. Groesgen Publisher: ISBN: Category : Box girder bridges Languages : en Pages : 70
Book Description
The Kansas Department of Transportation requested a study to examine the fatigue behavior of cope holes specifically to answer the question as to which AASHTO fatigue category governs cope holes. The goal of this project is to supplement the AASHTO Bridge Design Specification by providing experimental and analytical information for designers as to how to categorize cope holes in welded steel girders. The stress field in an idealized smooth cope hole, as well as a representative actual flame cut cope hole, was determined in an actual beam. The resulting stress field, as determined with experimental stress analysis techniques, revealed a serious stress concentration located near the top of the cope hole in the web. This stress field was confirmed in a comprehensive finite element study of a section of the beam assembly using both 2-D and 3-D analysis.
Author: Esteban Zecchin Publisher: ISBN: Category : Languages : en Pages : 654
Book Description
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
Author: Mark Douglas Bowman Publisher: Transportation Research Board ISBN: 030925826X Category : Technology & Engineering Languages : en Pages : 125
Book Description
"TRB's National Cooperative Highway Research Program (NCHRP) Report 721: Fatigue Evaluation of Steel Bridges provides proposed revisions to Section 7--Fatigue Evaluation of Steel Bridges of the American Association of State Highway and Transportation Officials Manual for Bridge Evaluation with detailed examples of the application of the proposed revisions."--Publisher's description.
Author: Sunghyun Park Publisher: ISBN: Category : Languages : en Pages : 378
Book Description
When analyzing steel I-girder bridges, the approach used to model cross-frames can significantly impact performance predictions for girder stability during construction and for cross-frame fatigue under in-service traffic loading. A common practice is to model cross-frame members as truss members subject to axial forces only. Recent research has shown that this approach can lead to erroneous predictions of cross-frame stiffness and cross-frame member forces. Actual cross-frames are typically constructed using single-angle members with gusset plate connections that introduce significant out-of-plane eccentricity and in-plane rotational restraint. These connection effects combined with the complex bending behavior of single-angles results in significant bending of the cross-frame members. This bending behavior can significantly change the axial stiffness of the cross-frame member and potentially introduce large errors in truss element models. The objective of this research is to study the behavior of cross-frames in steel I-girder bridges to better understand their stiffness and internal force distributions during in-service traffic loading on the completed bridge as well as during construction of the bridge. The research involves development of high-fidelity three-dimensional finite element models of steel I-girder bridge systems, with predicted cross-frame response validated using laboratory experimental data as well as data from field instrumentation of in-service bridges. The validated models are then used to conduct parametric finite element studies to examine a wide range of bridge and cross-frame geometries. Based on the results from the parametric studies, stiffness modification factor for truss element models is developed to improve the analysis of cross-frames in steel I-girder bridges
Author: Matthew Craig Reichenbach
Author: Matthew Craig Reichenbach
Author: Joshua Benjamin White
Author: Steffen P. Groesgen
Author: Esteban Zecchin
Author: Mark Douglas Bowman
Author: Sunghyun Park
Author: James A. Reisert
Author: Yongda Fu
Author: Heidi L. Hassel
Author: Prem P. Rimal