Download or read book Evaluation of Fatigue Design Load Models for Cross frames in Steel I girder Bridges written by Joshua Benjamin White and published by . This book was released on 2020 with total page 560 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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

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 Experimental and Analytical Evaluation of Cross frame Fatigue Behavior in Steel I girder Bridges written by Matthew Craig Reichenbach and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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

Download or read book Fatigue Evaluation of Steel Bridges written by Mark Douglas Bowman and published by Transportation Research Board. This book was released on 2012 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: "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.

Download or read book Sensitivity Analysis of Fatigue Evaluation of Steel Bridges written by Prem P. Rimal and published by . This book was released on 2001 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Evaluating the Role of Cross frames in Stress Distribution of Steel I girder Bridges by holistic Assessment of Finite Element Analysis Data written by Matija Radovic and published by . This book was released on 2017 with total page 261 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stress distributions of main bridge components (girders, deck and cross-frames were extracted) from the models and evaluated using “holistic” level approach. The “holistic” level approach refers to comprehensive assessment of all FEA stress distribution data, not only peak values. The results showed that by using “holistic” evaluation of stress distribution data, we were able to identify and quantify best performing cross-frame configuration. However, results also indicate that removing cross-frames from bridges did not substantially affected stress distributions throughout the bridge. This finding was further strengthen by Tensor decomposition analysis of stress distribution data. This method found that removing cross-frames from the bridge models did not affect substantially stress distributions at design load levels. Although, removing cross-frames from the bridge models did affect stress distribution at first yield and system yield load level, it did not affect overall system capacity of the bridge.

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 Live load Models for Design and Fatigue Evaluation of Highway Bridges written by and published by . This book was released on 2007 with total page 333 pages. Available in PDF, EPUB and Kindle. Book excerpt: New load design factors and models are introduced to account for site-specific live-load demands in the state of New Jersey. Live-load for highway bridges is highly site specific. The current AASHTO LRFD design specifications provide a notional design truck to which load factors are applied. These strength design factors were calibrated using reliability theory to provide a consistent level of safety for various spans and bridge types. The original calibration was done using a small sample of data from decades ago. Truck weights and volumes have significantly increased, reducing the level of safety of highway bridges designed today. Live-load is quantified using an extensive weigh-in-motion (WIM) database for the state of New Jersey as well as instrumentation at a bridge located in the heart of Port Newark, NJ. An integrated system combines a WIM system to measure truck loads and a data logger to capture the strains and deflections. This, first of its kind, system provides a complete picture of bridge behavior. The WIM data collected include all of the parameters needed to quantify truck loading: gross and axle weights, axle spacings, classification, counts, speeds, lane, etc. The bridge response includes parameters such as: strains and deflections. Information on truck loads are used to develop load effect envelopes for various span lengths. The load effects are then extrapolated using Normal probability paper to predict the maximum expected levels for the full service life of 75 years. The effect of other distributions, various measurement durations, and truck multiple presence is also studied. Based on the analysis of moment and shear envelops for various spans, it was found that the current load factors must be increased to maintain the level of safety that the code dictates. A new load model is proposed to provide a more uniform bias for New Jersey trucks. Fatigue load effects are studied in terms of effective truck weights, truck dimensions, and multiple presence in comparison with current evaluation procedures. Experimental load and response data from the instrumented bridge along with computer models is used to study the effect of truck weight, volume, and multiple presence of the fatigue life. Statistical techniques developed by the automotive industry are applied to short experimental measurements to predict a fatigue load profile that would be expected if measurement extended to a much longer duration. The rainflow extrapolation techniques utilize Extreme Value Theory and non-parametric smoothing methods to render a future prediction of the rainflow counted stress cycle matrix. The effect of measurement duration, seasonality, and truck multiple presence on fatigue life prediction is studied.

Download or read book Fatigue Evaluation Procedures for Steel Bridges written by Fred Moses and published by Transportation Research Board National Research. This book was released on 1987 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Analysis of the AASHTO Fatigue Design Provisions for Welded Steel Bridge Details Using Reliability Theory written by Benjamin Thomas Cross and published by . This book was released on 2007 with total page 101 pages. Available in PDF, EPUB and Kindle. Book excerpt: The current fatigue design provisions in the AASHTO LRFD Specifications (2004) are based on an allowable stress approach. Provisions for most limit states, however, have been updated to the more modern reliability-based Load and Resistance Factor Design (LRFD) approach. The primary objective of the reported research was to assess the reliability present in the AASHTO fatigue design specifications for welded steel bridge details such that more uniform design provisions can eventually be implemented. To accomplish this, a reliability model was developed assuming a log-log straight line fatigue resistance model. The statistical parameters of the variables included in the model were determined based on sound engineering judgment and values used in similar past studies. The safety indices present in the current design provisions were then evaluated. The results indicate that the safety level of the current design provisions varies by span length and by detail category. Therefore, a target safety index was selected based on those currently present in design and new design fatigue resistance coefficients were proposed such that the safety level of the fatigue specifications would be uniform across all detail categories for a given set of design conditions. In addition, the safety of the design variable amplitude fatigue limits was evaluated through the use of computer simulations. New variable amplitude fatigue limits were then proposed to correspond with the proposed design fatigue resistance coefficients.

Download or read book Fatigue Load Models for Girder Bridges written by Jeffrey A. Laman and published by . This book was released on 1995 with total page 544 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Development of LRFD Specifications for Horizontally Curved Steel Girder Bridges written by J. M. Kulicki and published by Transportation Research Board National Research. This book was released on 2006 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report contains the findings of research performed to develop design specifications for horizontally curved steel girder bridges.

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 Finite Element Analysis of Fatigue Prone Details of the Tuttle Creek Bridge written by and published by . This book was released on 2007 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many older steel girder bridges exhibit distortion-induced fatigue cracking at the cross-frame to girder connections. In a two-girder bridge like the Tuttle Creek Bridge there are no redundant load paths and this problem is of even greater concern. The primary girders of the bridge structure are fatigue critical elements and even when such cracks are relatively small they must be examined extensively. The Tuttle Creek Bridge, built in 1962, developed distortion-induced fatigue cracks in the web gap region. The crack prevention repairs of 1986 were not effective and continued crack growth was observed. The bridge was again repaired recently in the summer of 2005. A finite element study is performed in this study for a typical intermediate girder span, to characterize the behavior of fatigue critical details and to evaluate the effectiveness of the newly installed retrofits. A dual-level finite element analysis was performed using macro-level models of the entire bridge structure and micro-level models of some portions of the bridge under investigation. The finite element procedure was found to be efficient and accurate. The models were calibrated using field strain data obtained from two field tests done before and after the retrofits. The analytical results were in good agreement with the measured field data. The analysis shows that the top flange web gap region is the most susceptible to distortion-induced fatigue. The study successfully explains the observed crack patterns on the bridge. The study indicates a significant reduction in web gap stresses after the retrofit. The retrofit also reduces stresses in the gusset plate region and eliminates the stress concentration near the weld terminations. Based upon the most critical detail and assuming that the traffic volume doubles from the present ADTT of 65, the service life of the bridge is estimated to be over one hundred years.

Download or read book Finite Element Analysis and Design of Steel and Steel Concrete Composite Bridges written by Ehab Ellobody and published by Butterworth-Heinemann. This book was released on 2014-05-30 with total page 683 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, bridge engineers and researchers are increasingly turning to the finite element method for the design of Steel and Steel-Concrete Composite Bridges. However, the complexity of the method has made the transition slow. Based on twenty years of experience, Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges provides structural engineers and researchers with detailed modeling techniques for creating robust design models. The book’s seven chapters begin with an overview of the various forms of modern steel and steel–concrete composite bridges as well as current design codes. This is followed by self-contained chapters concerning: nonlinear material behavior of the bridge components, applied loads and stability of steel and steel–concrete composite bridges, and design of steel and steel–concrete composite bridge components. Constitutive models for construction materials including material non-linearity and geometric non-linearity The mechanical approach including problem setup, strain energy, external energy and potential energy), mathematics behind the method Commonly available finite elements codes for the design of steel bridges Explains how the design information from Finite Element Analysis is incorporated into Building information models to obtain quantity information, cost analysis

Download or read book Analysis of Distortion induced Fatigue Cracking in a Steel Trapezoidal Box Girder Bridge written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In 2006, a consulting firm was hired to perform an in-depth interior box inspection on Delaware Department of Transportation (DelDOT) Bridge Number 1-501, also known as the Newport Viaduct. Upon inspection, 655 fatigue cracks were observed, occurring at the weld metal between the transverse cross frame connection plate and girder webs. At the cracked locations, a 2.5 in. web gap exists between the connection plate termination and the girder flanges. This is a known fatigue prone detail that has been widely documented to be susceptible to out-of-plane deformation and distortion-induced fatigue. Although the mode of cracking is relatively familiar, there are remaining questions that should be answered to ensure the proper functioning of the structure. Specifically, is the observed fatigue cracking consistent with expected behavior? Secondly, should additional cracks be expected to initiate in locations that currently do not have observable cracks? These questions were approached by focusing on a portion of the overall structure, Spans 9-11 in the southbound direction. Field testing was performed to capture the in-situ response of the structure to known live loads via the implementation of 23 strategically placed strain transducers. The field testing was used to calibrate and validate a finite element model. The finite element mesh was constructed using the FEMAP preprocessor and solved using ABAQUS. Sensitivity analyses were performed on the model to investigate the influence of the transverse truck position within the travel lane, the concrete deck stiffness, and the concrete parapets. The results of each analysis showed that the finite element model was insensitive to variations in transverse truck position, concrete stiffness, and the exclusion of the parapets. The finite element model was ultimately utilized to perform a fatigue evaluation. The fatigue evaluation showed that fatigue cracking is within reason given the stress range and the number of accumulated stress cycles from lifetime truck traffic on the structure. The fatigue evaluation and anticipation of future cracking establishes the need for developing crack retrofit and mitigation strategies for the web gap details within the structure. These strategies will extend the longevity of the bridge and enable it to remain in service.

Download or read book Cross frame Stiffness Modification Factors for Composite Steel I girder Bridges written by Sunghyun Park and published by . This book was released on 2021 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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