RETROFITTING METHODS AGAINST FATIGUE CRACKING IN STEEL GIRDER WEB PENETRATION

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Chihiro Sakamoto ◽  
Masahiro Sakano ◽  
Hideyuki Konishi ◽  
Takashi Fujii
Keyword(s):  
Fatigue Life ◽  
Fatigue Cracking ◽  
Highway Bridges ◽  
Lower Surface ◽  
Strength Properties ◽  
Fatigue Tests ◽  
Stress Distributions ◽  
Steel Girder ◽  
Cracking Behavior ◽  
Weld Toe

Fatigue cracking in steel girder web penetration details is so dangerous that it can break steel girders. Since a number of highway bridges have such web penetration details in Japan, it is of urgent importance to grasp these fatigue strength properties and develop effective retrofitting methods. In a previous report, we investigated the stress distributions around web penetration details, and fatigue cracking behavior, using steel girder specimens with web penetration details. In this study, we investigate effects of retrofitting methods against fatigue cracking in web penetration details through fatigue tests using large girder specimens with web penetration details in which cross beam lower flanges are connected to lower surface of a slot by welding. Principal results obtained through this study are as follows: (1) Weld toe grinding can extend fatigue life more than 5 times, (2) Two-face attachment can extend fatigue life more than 10 times, and (3) Two-face attachment with weld toe grinding can extend fatigue life more than 25 times.

THREE FACE ATTACHMENT RETROFIT AGAINST FATIGUE CRACKING AT STEEL GIRDER WEB PENETRATION

2018 ◽  
Vol 5 (2) ◽  
Author(s):  
Chihiro Sakamoto ◽  
Masahiro Sakano ◽  
Hideyuki Konishi ◽  
Takashi Fujii
Keyword(s):  
Fatigue Strength ◽  
Stress Concentration ◽  
Stress Reduction ◽  
Fatigue Cracking ◽  
Highway Bridges ◽  
Lower Surface ◽  
Strength Properties ◽  
Fatigue Tests ◽  
Lower Side ◽  
Steel Girder

Fatigue cracking in steel girder web penetration details is so dangerous that it can break steel girders. Since a number of highway bridges have such web penetration details in Japan, it is of urgent importance to grasp these fatigue strength properties. In this study, we investigate stress reduction effects of three face attachment retrofit through fatigue tests using a large girder specimen with web penetration details where cross beam lower flanges are connected to the lower surface of a slot by welding. As a result, there is very little difference between two and three face attachments about stress reduction effects, while they are more effective than one face attachment. The upper side attachment is more effective than the lower side attachment, while both side attachment is best. Two and three face both side attachments can reduce about 40% of stress concentration, while two and three face upper side attachments can reduce 50– 60%.

FATIGUE TEST OF STEEL GIRDER WEB PENETRATION DETAILS WITH A SLIT

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
Naoto Yoshida ◽  
Masahiro Sakano ◽  
Hideyuki Konishi ◽  
Takashi Fujii
Keyword(s):  
Fatigue Strength ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Fatigue Cracking ◽  
Highway Bridges ◽  
Strength Properties ◽  
Fatigue Tests ◽  
Bottom Surface ◽  
Steel Girder ◽  
Propagation Behavior

Fatigue cracking in steel girder web penetration details is so dangerous that it can break steel girders. A one-meter-long crack was detected in Yamazoe Bridge in 2006. Since a number of highway bridges with such web penetration details may exist in Japan, it is of urgent importance to understand these fatigue-strength properties. However, few fatigue tests have been reported on steel girder web penetration details. The purpose of this study is to clarify fatigue behavior of steel girder web penetration details with a slit through fatigue tests of specimens with these details. We designed and fabricated girder specimens that have steel girder web penetration details, in which cross-beam bottom flanges are connected to each top or bottom surface of a slit by welding. First, we conducted static loading tests to understand the stress distributions around web penetration details. Second, we conducted fatigue tests to examine fatigue crack initiation and propagation behavior and fatigue strength.

Cumulative Damage Behavior of Anisotropic Al-6061-T6 as a Function of Axial-Torsional Loading Mode Sequence

1994 ◽  
Vol 116 (1) ◽  
pp. 27-34 ◽  
Author(s):  
Hong Lin ◽  
Hamid Nayeb-Hashemi ◽  
Charles A. Berg
Keyword(s):  
Damage Accumulation ◽  
Low Cycle Fatigue ◽  
Constitutive Relations ◽  
Fatigue Cracking ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Cracking Behavior ◽  
Al 6061 ◽  
Damage Models ◽  
Loading Mode

Two types of low cycle fatigue tests were conducted along two principal orthotropic directions of an orthotropic Al-6061-T6 plate in strain control at room temperature: (1) reference fatigue tests under three loading conditions: push-pull, torsion, and combined push-pull/torsion in-phase; (2) sequential fatigue tests in which different sequences of push-pull and torsion were performed. Fatigue cracking behavior was observed during all of the fatigue tests. Shear cracking dominated the damage of the material. Anisotropic constitutive relations of the material were used in the evaluation of several multiaxial fatigue damage models. The predictive capabilities of these models were assessed based on the results of reference fatigue tests. The damage accumulation behavior of the material was found to depend on the sequence of the loading mode. For the sequence of torsion then push-pull, the damage summation was greater than unity. However, for the sequence of push-pull then torsion, the damage accumulation was near unity as predicted by the linear damage rule. A nonlinear damage accumulation rule could represent the results of the sequential fatigue tests.

Effect of Residual Stress, Temperature and Adhesion on Wheel Surface Fatigue Cracking

2008 ◽  
Author(s):  
Daniel H. Stone ◽  
Scott M. Cummings
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Contact Stress ◽  
Fatigue Cracking ◽  
Fatigue Tests ◽  
Operating Conditions ◽  
Defect Prevention ◽  
Class C ◽  
Research Consortium

The Wheel Defect Prevention Research Consortium (WDPRC) conducted an analysis pertaining to the fatigue cracking of wheel treads by incorporating the effects of residual stresses, temperature, and wheel/rail contact stress. Laboratory fatigue tests were conducted on specimens of wheel tread material under a variety of conditions allowing the analysis to properly account for the residual stresses accumulated in normal operating conditions. Existing literature was used in the analysis in consideration of the effects of contact stress and residual stress relief. This project was performed to define a temperature range in which the life of an AAR Class C wheel is not shortened by premature fatigue and shelling. Wayside wheel thermal detectors are becoming more prevalent on North American railroads as a means of identifying trains, cars, and wheels with braking issues. Yet, from a wheel fatigue perspective, the acceptable maximum operating temperature remains loosely defined for AAR Class C wheels. It was found that residual compressive circumferential stresses play a key role in protecting a wheel tread from fatigue damage. Therefore, temperatures sufficient to relieve residual stresses are a potential problem from a wheel fatigue standpoint. Only the most rigorous braking scenarios can produce expected train average wheel temperatures approaching the level of concern for reduced fatigue life. However, the variation in wheel temperatures within individual cars and between cars can result in temperatures high enough to cause a reduction in wheel fatigue life.

Controlled Weld Toe Profiles for Fatigue Life Extension of T-Butt Joints: An Application to FSOs & FPSOs

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
J. Efraín Rodríguez-Sánchez ◽  
Alejandro Rodríguez-Castellanos ◽  
Manuel F. Carbajal-Romero ◽  
Efrén Ayala-Uraga
Keyword(s):  
Fatigue Life ◽  
Fracture Mechanics ◽  
Fatigue Cracking ◽  
Life Extension ◽  
Design Stage ◽  
Element Analysis ◽  
Profile Control ◽  
Hull Structure ◽  
Weld Toe ◽  
Dry Dock

Application of controlled weld toe profiles can be considered an option to extend the fatigue life of welded connections when ongoing tankers are converted in dry docks to serve like offshore ships (FPSOs and FSOs). Very slim chances to implement such fatigue improvement will arise when these vessels are in service, since a converted ship is designed to be inspected, maintained, and repaired in situ and not in dry dock as it is uneconomical to interrupt production. Codes recognize fatigue life extension by means of a controlled weld toe profile (2004, NORSOK Standard N-004 Rev. 2 October). Application of a controlled weld toe profile during conversion in selected areas previously identified by stress analysis of the hull structure can lead to extend the converted vessel fatigue life to comply with an expected field life. The American Bureau of Shipping S-N curves allow a credit of 2.2 on fatigue life when suitable toe grinding and NDE are provided. A controlled weld toe profile can be applied during dry dock ship conversion to FSO or FPSO to welds in a noncracked condition but that were identified prone to fatigue cracking in a stress assessment analysis under new service conditions. Credit on fatigue life in various codes and results from experimental data obtained from fatigue tested specimens with a controlled weld toe profile are given. Comments on the design of a controlled weld toe profiles and recommendations based on experimental experience for the implementation of equipment to perform a controlled weld toe profile are also given. A fracture mechanics approach for the assessment of controlled weld toe profiles for fatigue life extension purposes is described. Initially, a comparison of stress concentration factors for a typical T-butt ship hull plate connection with and without weld toe profile control determined by finite element analysis (FEA) is presented. Results obtained from the FEA connection such as through plate stress distribution are used in a fracture mechanics analysis to compare the fatigue crack growth curve in as-welded condition to that with controlled weld toe profile. It is demonstrated that weld toe profile control is a feasible method to be implemented to improve fatigue life in the order of 2 of T-butt welded connections of ships, which are under conversion to serve as FPSOs or FSOs. This fatigue life extension factor should not be considered at the design stage.

The Effect of Residual Stress on Fatigue Life of Welded Cruciform Joints of 16MnR for Train Bogie

2013 ◽  
Vol 815 ◽  
pp. 695-699 ◽  
Author(s):  
Ying Xia Yu ◽  
Bo Lin He ◽  
Jian Ping Shi ◽  
Jing Liu
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Fatigue Life ◽  
Load Ratio ◽  
Fatigue Tests ◽  
Residual Tensile Stress ◽  
Cruciform Joints ◽  
Weld Toe ◽  
Deformation Layer ◽  
Cruciform Joint

The weld toe surface and its nearby area of welded cruciform joints were treated by ultrasonic impact. Under the same stress concentration and after heat treatment to eliminate residual stress, the effect of residual stress on the fatigue life of joint was researched. The fatigue tests are performed on the joints of 16MnR both for the un-treated and treated joints by using EHF-EM200K2-070-1A type fatigue tester when the load ratio is 0.1, frequency is 10Hz. The experimental results indicate that the severe plastic deformation in the vicinity of weld toe surface was formed by impact treating for 2 minutes, the thickness of the plastic deformation layer is about 60μm. Residual tensile stress in the weld toe surface can be changed to residual compressive stress by impact treatment. The fatigue life of welded joint is 0.260×106cycle, and the fatigue life of treated joint is 0.499×106cycle. Compared to the un-treated joint, the fatigue life of treated joint has been increased by 91.92%. The residual stress contributed to fatigue life is about 16%. Residual stress has great effect on the fatigue life of welded cruciform joint.

FATIGUE BEHAVIOR AT THE UPPER END OF VERTICAL STIFFENERS CONNECTED WITH SWAY BRACINGS

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Chihiro Sakamoto ◽  
Masahiro Sakano ◽  
Hideyuki Konishi ◽  
Masahiro Koyama
Keyword(s):  
Fatigue Behavior ◽  
Fatigue Cracking ◽  
Fatigue Tests ◽  
Large Specimen ◽  
Cracking Behavior ◽  
Girder Bridges ◽  
Bead Surface ◽  
Rc Slab ◽  
Vertical Stiffener

Lots of fatigue crackings were reported at the upper end of vertical stiffeners connected to sway bracings in steel highway girder bridges. In this study, we investigate fatigue cracking behavior at the upper end of vertical stiffeners under RC slab, through fatigue tests using a large specimen with three main girders under alternative loading using two actuators. As a result, alternative loading can reproduce the alternative stress at the upper end of vertical stiffener in the middle girder when vehicles run on the driving lane and passing lane alternatively. Root cracks were initiated after 0.1 Mcycles loading and appeared on the bead surface when 0.6 Mcycles.

scholarly journals Mechanistic and Economical Characteristics of Asphalt Rubber Mixtures

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Mena I. Souliman ◽  
Annie Eifert
Keyword(s):  
Fatigue Life ◽  
Fatigue Cracking ◽  
Advanced Characterization ◽  
Fatigue Tests ◽  
Modified Asphalt ◽  
State Highway ◽  
Asphalt Rubber ◽  
Mechanistic Analysis ◽  
Characterization Procedure ◽  
The Impact

Load associated fatigue cracking is one of the major distress types occurring in flexible pavement systems. Flexural bending beam fatigue laboratory test has been used for several decades and is considered to be an integral part of the new superpave advanced characterization procedure. One of the most significant solutions to prolong the fatigue life for an asphaltic mixture is to utilize flexible materials as rubber. A laboratory testing program was performed on a conventional and Asphalt Rubber- (AR-) gap-graded mixtures to investigate the impact of added rubber on the mechanical, mechanistic, and economical attributes of asphaltic mixtures. Strain controlled fatigue tests were conducted according to American Association of State Highway and Transportation Officials (AASHTO) procedures. The results from the beam fatigue tests indicated that the AR-gap-graded mixtures would have much longer fatigue life compared with the reference (conventional) mixtures. In addition, a mechanistic analysis using 3D-Move software coupled with a cost analysis study based on the fatigue performance on the two mixtures was performed. Overall, analysis showed that AR modified asphalt mixtures exhibited significantly lower cost of pavement per 1000 cycles of fatigue life per mile compared to conventional HMA mixture.

Effect of Toe Grinding on Fatigue Strength of Ship Structure

2008 ◽  
Vol 24 (03) ◽  
pp. 152-160 ◽  
Author(s):  
Hong Ryeul Ryu ◽  
Wha Soo Kim ◽  
Woo Il Ha ◽  
Sung Won Kang ◽  
Myung Hyun Kim
Keyword(s):  
Fatigue Life ◽  
Crack Propagation ◽  
Enhancement Factor ◽  
Research Work ◽  
Fatigue Tests ◽  
Special Equipment ◽  
Structural Shape ◽  
Actual Structure ◽  
Weld Toe ◽  
Crack Initiation Life

It is well known that grinding the weld toe is not only effective in increasing the fatigue life at the weld joint by removing the initial defect and by reducing the stress concentration, but also rather convenient to apply and survey at the construction stage without special equipment or techniques. In this research work, comparative fatigue tests have been performed for a total of five types of weld specimens: three types of small welded specimens and two types of small-scaled structural models. According to the results of the fatigue tests, the enhancement factor of fatigue life by toe grinding for small welded specimens is determined to be about 6 to 10. However, the enhancement factor of fatigue life by toe grinding for small-scaled structure is 1.9 to 5.4. In the case of small welded specimens, once the crack is initiated to a certain level, then the crack propagation is accelerated rapidly due to simplicity of structural shape. In the case of actual ship structures, however, even after the crack is initiated to a certain level, the crack propagation is not accelerated as much due to structural redundancy. The toe grinding is only beneficial in extending the crack initiation life. Accordingly, the effect of toe grinding on the fatigue life at the actual structure is not as predominant as the one at the small welded specimen.

Controlled Weld Toe Profiles for Fatigue Life Extension in FSO’s and FPSO’s

2007 ◽  
Author(s):  
J. Efrai´n Rodri´guez-Sa´nchez ◽  
Alejandro Rodri´guez-Castellanos ◽  
Manuel F. Carbajal-Romero ◽  
Efre´n Ayala-Uraga
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fracture Mechanics ◽  
Fatigue Cracking ◽  
Life Extension ◽  
Element Analysis ◽  
Profile Control ◽  
Hull Structure ◽  
Weld Toe ◽  
Plate Connection

Application of controlled weld toe profiles can be considered an option to extend the fatigue life of welded connections when ongoing tankers are converted in dry docks to serve like offshore ships (FPSOs and FSOs). Very slim chances to implement such fatigue improvement will arise when these vessels are in service, since a converted ship is designed to be inspected, maintained and repaired in situ and not in dry dock as it is uneconomical to interrupt production. Codes recognize fatigue life extension by means of a controlled weld toe profile, e.g. [1]. Application of a controlled weld toe profile during conversion in selected areas previously identified by stress analysis of the hull structure can lead to extend the converted vessel fatigue life to comply with an expected field life. The American Bureau of Shipping S-N curves allow a credit of 2.2 on fatigue life when suitable toe grinding and NDE are provided. A controlled weld toe profile can be applied in fatigue crack repaired welds during ship conversion or even on those that during ship conversion are found in a non-cracked condition but were identified prone to fatigue cracking in a stress assessment analysis under in-service conditions. Credit on fatigue life in various codes and results from experimental data obtained from fatigue tested specimens with a controlled weld toe profile are given. Comments on the design of a controlled weld toe profiles and recommendations based on experimental experience for the implementation of equipment to perform a controlled weld toe profile are also given. A Fracture Mechanics approach for the assessment of controlled weld toe profiles for fatigue life extension purposes is described. Initially, a comparison of SCFs for a typical ship hull plate connection with and without weld toe profile control determined by Finite Element Analysis (FEA) is presented. Then, results obtained from the FEA connection such as through plate stress distribution are used in a Fracture Mechanics Analysis to compare the fatigue crack growth curve in as-welded condition to that with controlled weld toe profile.

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