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Analysis Of Girder Differential Deflection And Web Gap Stress For Rapid Assessment Of Distortional Fatigue In Multi Girder Steel Bridges
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Book Synopsis Analysis of Girder Differential Deflection and Web Gap Stress for Rapid Assessment of Distortional Fatigue in Multi-girder Steel Bridges by : Huijuan Li
Download or read book Analysis of Girder Differential Deflection and Web Gap Stress for Rapid Assessment of Distortional Fatigue in Multi-girder Steel Bridges written by Huijuan Li and published by . This book was released on 2005 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: Distortion-induced fatigue cracking in unstiffened web gaps is common in steel bridges. Previous research by the Minnesota Department of Transportation (Mn/DOT) developed methods to predict the peak web gap stress and maximum differential deflection based upon field data and finite element analyses from two skew supported steel bridges with staggered bent-plate and cross-brace diaphragms, respectively. This project aimed to test the applicability of the proposed methods to a varied spectrum of bridges in the Mn/DOT inventory. An entire bridge model (macro-model) and a model encompassing a portion of the bridge surrounding the diaphragm (micro-model) were calibrated for two instrumented bridges. Dual-level analyses using the macroand micro-models were performed to account for the uncertainties of boundary conditions. Parameter studies were conducted on the prototypical variations of the bridge models to define the sensitivity of diaphragm stress responses to typical diaphragm and bridge details. Based on these studies, the coefficient in the web gap stress formula was calibrated and a linear prediction of the coefficient was proposed for bridges with different span lengths. Additionally, the prediction of differential deflection was calibrated to include the influence of crossbrace diaphragms, truck loading configurations and additional sidewalk railings. A simple approximation was also proposed for the influence of web gap lateral deflection on web gap stress. This research studied the effect of two enzymes as soil stabilizers on two soil types to determine how and under what conditions they function. Researchers evaluated the chemical composition, mode of action, resilient modulus, and shear strength to determine the effects of the enzymes A and B on the soils I and II. The enzymes produced a high concentration of protein and observations suggest the enzymes behave like a surfactant, which effects its stabilization performance. The specimens were subjected to testing of varying lengths of time to determine their performance. Researchers observed an increase in the resilient modulus as the curing time increased but that an increase in application rate, as suggested by manufacturers, did not improve the performance of the enzymes. The study also suggests noticeable differences between the two enzymes and their effects on the soils in terms of resilient modulus and the stiffness of the soil.
Book Synopsis Analysis Tools and Rapid Screening Data for Assessing Distortional Fatigue in Steel Bridge Girders by : Evan Berglund
Download or read book Analysis Tools and Rapid Screening Data for Assessing Distortional Fatigue in Steel Bridge Girders written by Evan Berglund and published by . This book was released on 2001 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Distortion-induced Fatigue in Multi-girder Steel Bridges by : Dmitri Jajich
Download or read book Distortion-induced Fatigue in Multi-girder Steel Bridges written by Dmitri Jajich and published by . This book was released on 2000 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report summarizes the findings of a project with the following goals: to implement a field instrumentation and monitoring program for a typical multi-girder steel bridge on skew supports that may be susceptible to web-gap distortion; to assess the frequency and magnitude of the distortional fatigue stresses at the web-stiffener connections; and to evaluate the impact of these stresses on fatigue life. Measurements from 12 independent strain gauges were continuously monitored and recorded for more than three months on Minnesota Department of Transportation (Mn/DOT) bridge #27734. Truck loading tests also were conducted. Predicted web-gap fatigue life based on the long-term monitoring data from Mn/DOT bridge #27734 ranges from 45 to 75 years. Comparison of web-gap stresses with primary design stresses reveals that web-gap distortional stresses are comparatively high. The report also highlights a detailed finite element study to better understand the web-gap stress mechanism and to compare experimental results with theoretical predictions. Study results have important implications for investigators of distortion-induced web-gap fatigue. They indicate that the actual stress at the so-called hotspot may be as much as twice the stress measured at the strain gauge. The report includes a method for estimating girder deflections and web-gap stress.
Book Synopsis Rapid Assessment of Distortional Stresses in Multi-girder Steel Bridges by : Benjamin Severtson
Download or read book Rapid Assessment of Distortional Stresses in Multi-girder Steel Bridges written by Benjamin Severtson and published by . This book was released on 2004 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multi-girder steel bridges are found as part of the transportation infrastructure of countries throughout the world. These bridges are typically constructed with a steel reinforced concrete deck rigidly attached to the top flange of steel girders. The deck and the transverse steel members distribute loads laterally between bridge girders. The weld connecting transverse stiffeners to the girder web are commonly terminated several inches away from the girder flanges to avoid overlapping with the web-to-flange connection weld, leaving a short, unstiffened portion of the girder web-the web gap. The large flexibility of the web gap region relative to the other components forces it to accommodate the majority of the distortion. Since 1998, several research efforts have investigated methods for predicting the amount of web gap stress a bridge will experience during its service life. Phase I of this research resulted in a simple equation for estimating web gap stress using data collected during field testing and subsequent finite modeling of a skew supported bridge with staggering bent-plate diaphragms. Phase II produced an approximate method for predicting diaphragm differential deflection of skew supported bridges with bent-plate diaphragms. The combined result of Phase I and Phase II was a useful method for predicting peak web gap stress in skewed multi-girder steel bridges with staggered bent-plate diaphragms. The next step was to develop a reliable procedure for the rapid assessment of distortional stresses in steel bridges that includes a test of the applicability of this procedure to bridges with geometries differing from those that formed the basis of the previous research. As a consequence of this most current research, the authors propose changes and recommend modifications of previously developed methods of field measurement and assessment.
Book Synopsis Rapid Assessment of Girder Differential Deflection and Distortional Fatigue Stress in Multi-girder Steel Bridges by : Huijuan Li
Download or read book Rapid Assessment of Girder Differential Deflection and Distortional Fatigue Stress in Multi-girder Steel Bridges written by Huijuan Li and published by . This book was released on 2005 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Field Testing and Finite Element Analysis of Retrofit Methods for Distortion-induced Fatigue in Steel Bridges by : Yared Shifferaw Bayleyegn
Download or read book Field Testing and Finite Element Analysis of Retrofit Methods for Distortion-induced Fatigue in Steel Bridges written by Yared Shifferaw Bayleyegn and published by . This book was released on 2005 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: Crack formation due to out-of-plane distortion in the web-gap region has been a common occurrence in multi-girder steel bridges. These cracks result from the fatigue stresses that are induced in the web-gap due to cyclic diaphragm forces resulting from differential deflections between girders. The study presented herein investigated the different repair methods that can be used to control formation of these cracks. The study involved field testing and analytical modeling of a skewed multi-girder steel bridge designated as Design No. 1283, which is built on county road D-180 that crosses over I-380 in the state of Iowa. Different repair methods were suggested to reduce the induced stresses and strains in the web-gap under truck loads. These methods included loosening of the bolts connecting the cross-bracing to the stiffener, connecting the stiffener to the girder top flange or adding another stiffener on the opposite side of the girder web. The results indicated that the first two of these repair alternatives were effective in reducing induced stresses and strains in the web-gap region. The impact of web-gap height on the distortion induced in the web-gap was also studied. Furthermore, influence surfaces for different responses such as, web-gap strains, stresses, out-of-plane displacements at critical locations, and forces in the adjacent diaphragm were developed. Moreover, relationships between the relative out-of-plane displacements and vertical stresses induced within the web-gap region were also provided. These developed relationships and surfaces serve as a quick estimate of induced stresses at critical locations in other web-gap regions of the bridge.
Book Synopsis Girder Differential Deflection and Assessing Distortional Fatigue in Skewed Steel Bridges by : Evan Matthew Berglund
Download or read book Girder Differential Deflection and Assessing Distortional Fatigue in Skewed Steel Bridges written by Evan Matthew Berglund and published by . This book was released on 2002 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Analysis of Distortion-induced Fatigue Cracking of a Trapezoidal Steel Box Girder Bridge Including Retrofit Investigation by :
Download or read book Analysis of Distortion-induced Fatigue Cracking of a Trapezoidal Steel Box Girder Bridge Including Retrofit Investigation written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Distortion induced fatigue is a common problem for aging steel bridges. The distortion creates secondary bending stresses at web gap locations that are not accounted for in design, thereby initiating fatigue cracks. A large number of such distortion-induced fatigue cracks have recently been found on Delaware Bridge 1-501 in Newport, Delaware. This multi box steel tub girder bridge has cracking that has initiated in the weld which connects the web to the internal bracing via connection plates. To investigate this problem, global finite element models of two of the bridge's spans were created. In order to calibrate the models for use in analysis, a diagnostic load test was performed using strain transducers to measure strains associated with bending of the girders. Once the models were found to reasonably represent the actual response of the structure, the model was then refined for local modeling of the web gap region. As expected, stresses within the gap were found to be large. Reduction of the stresses within these gap locations is required to increase the remaining life of the bridge. Several retrofit methods were designed to accomplish this stress reduction, based on effective retrofits used to correct similar problems in the past. These retrofit methods include drilling holes at the crack tips, positively attaching the connection plates to flanges, increasing the length of the web gaps, and removing the diagonal elements in the diaphragms. The retrofits were modeled and analyzed under fatigue loading and the resulting stresses were compared to the original structure. Of these methods, the positive attachment was found to be most effective in reducing the web gap stresses; however, all of the approaches provided significant reductions in the stress range. Recommendations for applying this type of retrofit detail along with the drilling of holes at the end of crack tips are provided.
Book Synopsis Rapid Assessment and Decision Making Strategies for Distortional Fatigue in Multi-girder Steel Bridges by : Benjamin Mark Severtson
Download or read book Rapid Assessment and Decision Making Strategies for Distortional Fatigue in Multi-girder Steel Bridges written by Benjamin Mark Severtson and published by . This book was released on 2003 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Finite Element Analysis of Fatigue Prone Details of the Tuttle Creek Bridge by :
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.
Book Synopsis Heat-straightening Repair of Damaged Steel Bridge Girders by : Robert J. Connor
Download or read book Heat-straightening Repair of Damaged Steel Bridge Girders written by Robert J. Connor and published by Transportation Research Board. This book was released on 2008 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: TRB¿s National Cooperative Highway Research Program (NCHRP) Report 604: Heat-Straightening Repair of Damaged Steel Bridge Girders: Fatigue and Fracture Performance explores limits, based on fatigue and fracture performance, on the number of damage and repair cycles to which damaged steel bridge girders may be subjected using the heat-straightening procedure.
Book Synopsis Guidelines for Analysis Methods and Construction Engineering of Curved and Skewed Steel Girder Bridges by :
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.
Book Synopsis Analysis of Distortion-induced Fatigue Cracking in a Steel Trapezoidal Box Girder Bridge by :
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.
Book Synopsis Analysis Tools and Rapid Screening Data for Distortional Fatigue in Steel Bridge Girders by :
Download or read book Analysis Tools and Rapid Screening Data for Distortional Fatigue in Steel Bridge Girders written by and published by . This book was released on 2001 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Development of LRFD Specifications for Horizontally Curved Steel Girder Bridges by : J. M. Kulicki
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. This book was released on 2006 with total page 81 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.
Book Synopsis Diaphragm Bolt Loosening Retrofit for Web Gap Fatigue Cracking in Steel Girder Bridges by : David Joseph Tarries
Download or read book Diaphragm Bolt Loosening Retrofit for Web Gap Fatigue Cracking in Steel Girder Bridges written by David Joseph Tarries and published by . This book was released on 2002 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many of Iowa's multiple steel girder bridges have shown signs of fatigue cracking due to out-of-plane deflection of the girder web near diaphragm connections. This fatigue prone web gap area is located in the negative moment regions of the girders where the stiffeners with diaphragms are not attached to the top flange of the girders. The Iowa Department of Transportation (Iowa DOT) has attempted to stop fatigue crack propagation but with limited success. For this reason the Iowa DOT has requested research on a new field retrofit to loosen the bolts in the connection between the diaphragm and the girders. The intent of this research is to show that loosening the bolts at the diaphragm/girder connections in steel girder bridges is effective in reducing strain and fatigue in the web gap. Select web gaps in negative moment regions on three heavily traveled bridges were instrumented with strain gages and deflection transducers to measure changes in the web gap due to the retrofit. Each bridge had a different diaphragm type: I-beam, channel, and X-brace. Field tests, using loaded trucks of known weight and configuration, were conducted on the bridge before and after implementing the bolt loosening retrofit. Short-term retrofit testing was conducted in the I-beam and channel diaphragm bridges. A long-term continuous monitoring test was completed on the X-braced bridge. Data was collected over a number of months with ambient truck traffic crossing the bridge. Data of significant load was recorded for analysis to support that the results of loosening the bolts do not change over time. Results indicate that loosening the diaphragm bolts reduces out-of-plane deflection and strain in the web gaps, as well as almost completely eliminating the strain in the diaphragms between the girders. The reduction in strain correlates to a reduction if not an elimination of fatigue cracking in the web gaps and an increase of in-service life of the bridge.
Book Synopsis Finite Element Based Fatigue Evaluation of Cope Holes in Bridge Girders by : Steffen P. Groesgen
Download or read book Finite Element Based Fatigue Evaluation of Cope Holes in Bridge Girders written by Steffen P. Groesgen and published by . This book was released on 1995 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
