› › Analysis Of Distortion Induced Fatigue Cracking Of A Trapezoidal Steel Box Girder Bridge Including Retrofit Investigation

Analysis of Distortion-induced Fatigue Cracking of a Trapezoidal Steel Box Girder Bridge Including Retrofit Investigation

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Publisher :

Page : pages

File Size : 20,78 MB

Release : 2009

Category : Bridges

ISBN : 9781109386073

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Book Description

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.



Analysis of Distortion-induced Fatigue Cracking in a Steel Trapezoidal Box Girder Bridge

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Page : pages

File Size : 24,42 MB

Release : 2009

Category : Bridges

ISBN : 9781109385977

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Book Description

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.





Fatigue Life Analysis of a Steel Trapezoidal Box Girder Bridge Using Measured Strains

Author : Jose Luis Soto Fuentes

Publisher :

Page : pages

File Size : 21,93 MB

Release : 2011

Category : Box beams

ISBN :

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Book Description

The Newport Viaduct is a 1,984 feet long bridge owned by the Delaware Department of Transportation located in Newport, DE. During an in-depth inspection in 2006, approximately 665 cracks were discovered near the internal cross frame diaphragm connection plates and the girder webs. A 2.5 inch gap exists between the termination of the diaphragm connection plate and the flanges of the girder. This is a known fatigue prone detail subject to out of plane deformations which lead to the formation of distortion induced fatigue cracks. Previous research done on the Newport Viaduct used global finite element models to estimate the fatigue life of the web gap details and analyze potential retrofit options. The purpose of this project is to measure site specific strains caused by variable traffic loads and use this data to carry out a fatigue life analysis of the web gap details. In order to assist in the fatigue life analysis, localized finite element models of the web gap details were created. Given geometric differences, separate models were created for the top and bottom web gap details. The finite element models were created using FEMAP and solved using ABAQUS. The analysis results showed a high stress gradient in the web gap region with a maximum near the weld toe. Moreover, the results showed that the bottom web gap detail experienced higher stresses than the top web gap detail given the same loading. In-service monitoring of the Newport Viaduct was carried out for 23 days. Resistive foil type strain gages were installed directly in the top and bottom web gap regions and data was collected and processed at 100Hz using the Rainflow algorithm to count the number of load cycles and their magnitude. The recorded data was used in conjunction with the bottom web gap finite element model and Miner's Rule to determine an effective stress at the weld toe. The results predict a mean fatigue life of 22 years for the bottom web gap detail. Furthermore, current uncracked web gap details are expected to crack in the future.



Fatigue Evaluation of Steel Bridges

Author : Mark Douglas Bowman

Publisher : Transportation Research Board

Page : 125 pages

File Size : 16,87 MB

Release : 2012

Category : Technology & Engineering

ISBN : 030925826X

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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.



Repair of Distortion-induced Fatigue Damage in Bridge No. 135-87 (043SB and 044NB) Using Newly-developed Strengthening Schemes

Author : Kathleen S. McElrath

Publisher :

Page : 126 pages

File Size : 13,83 MB

Release : 2016

Category :

ISBN :

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Book Description

A steel girder twin bridge structure located near Park City, Kansas, has experienced extensive distortion-induced fatigue cracking in its web-gap regions. Due to the bridge's skewed, staggered configuration, the majority of these cracks have occurred in the bottom web-gap region. The bridge was previously the subject of a series of detailed finite element analyses that investigated the effectiveness of several types of retrofits in repairing its distortion-induced fatigue cracks. One of these retrofits, the "angles-with-plate" retrofit, was developed and tested at the University of Kansas as a new retrofitting technique aimed at providing a more economical and easy-to-install distortion-induced fatigue cracking repair. The retrofit is made up of a pair of angles and a backing plate that connect the cross-frame connection plate and girder web in order to stiffen the web-gap region. Results from the finite element analyses determined that the angles-with-plate retrofit was the most effective and economical choice for repairs in the bridge, and plans were made for its installation. To investigate the performance of the angles-with-plate retrofit, two field tests were performed that monitored behavior of the bridge both before and after the retrofit was installed. Results from these field tests were compared with results from complementary finite element analyses to determine the overall effectiveness of the retrofit. In the bottom web-gap region, where cracking is most prevalent in the bridge, the angles-with-plate retrofit was successful at lowering stress demands that would lead to crack propagation. The same conclusion could not clearly be made for all cases in the bridge's less problematic top web-gap region, so a secondary set of finite element analyses was performed to gain a better understanding of what was happening in that region. Further analyses of the two common types of distortion-induced fatigue cracking determined that, while not always large, the angles-with-plate retrofit was successful in reducing stress demands in the top web-gap region. Therefore, it was concluded that the angles-with-plate retrofit was an effective repair for the problematic bottom web-gap regions of the bridge, and if needed, can be used effectively in the less demanding top web-gap region.



Finite Element Analysis of Fatigue Prone Details of the Tuttle Creek Bridge

Author :

Publisher :

Page : 108 pages

File Size : 41,36 MB

Release : 2007

Category : Finite element method

ISBN :

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Book Description

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.



Enhancement of Welded Steel Bridge Girders Susceptible to Distortion-induced Fatigue

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Publisher :

Page : 448 pages

File Size : 23,47 MB

Release : 2014

Category :

ISBN :

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Book Description

The goal of this study was to develop and evaluate the performance of retrofit techniques for existing steel bridges that have already sustained damage due to distortion-induced fatigue, or are anticipated to experience distortion-induced fatigue cracking within their design life. A second goal was to evaluate the use of new technologies and materials for repairing distortion-induced fatigue damage in steel bridges. While a number of retrofit techniques exist for repairing distortion-induced fatigue cracking, many of them require partial or full bridge closure to perform the repair. The retrofits developed under this project are intended to be able to be installed with minimal disturbance to traffic. Four primary subject matters are reported on within this document: (1) the development of the "angles-with-plate" distortion-induced fatigue repair; (2) development of fiber reinforced polymer (FRP) repairs for distortion-induced fatigue and in-plane fatigue; (3) development of Piezoelectric Induced Compressive Kinetics (PICK) technology for treatment of crack-arrest holes; and (4) a series of analytical investigations aimed at better understanding distortion-induced fatigue susceptibility of skewed bridge systems.



Field Testing and Finite Element Analysis of Retrofit Methods for Distortion-induced Fatigue in Steel Bridges

Author : Yared Shifferaw Bayleyegn

Publisher :

Page : 194 pages

File Size : 29,91 MB

Release : 2005

Category :

ISBN :

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Book Description

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.



Use of Adhesives to Retrofit Out-of-plane Distortion Induced Fatigue Cracks

Author : Yuying Hu

Publisher :

Page : 664 pages

File Size : 22,48 MB

Release : 2005

Category : Girders

ISBN :

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Book Description

Prior to 1985, it was common practice to avoid welding the connection plates to the tension flange of the girders of steel bridges. However, extensive fatigue cracking has developed in the unstiffened web gaps because of out-ofplane distortion. A new retrofit option was investigated that uses a room-temperature-cured two-part epoxy (3M Adhesive DP460-NS) to join a small length of 3/4-inch thick steel angle to the tension flange and the connection plate. A field test on two skewed bridges showed that the adhesive-angle retrofit system decreased the out-of-plane strain range by 40 to 50% when the original strain range was more than 50 microstrains. The ten adhesive-angle retrofits remained in place and were in good condition after three and a half years, suggesting that the chosen adhesive had good environmental durability. A laboratory large-scale specimen test with 8 web gaps showed that the retrofit system stopped or retarded most cracks even without stop holes when the measured out-of-plane strains were approximately 600 microstrains. Coupon tests conducted to investigate the environmental durability of the chosen adhesive showed that the chosen adhesive is suitable for applications at room or low temperature, even with high relative humidity.