Faculty Profiles - HANJI Takeshi

Papers - HANJI Takeshi

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Local strain approach to extremely low cycle fatigue assessment for thick-walled steel pier with box section

Tao Chen, Kazuo Tateishi, Takeshi Hanji

Proceedings of the 9th Korea-Japan Joint Seminar on Steel Bridges page： 235-246 2007.8

Language：English Publishing type：Research paper (scientific journal)

In a seismic event, steel piers may undergo large strain fluctuations of typically one to tens of cycles. That will possibly result in fracture of base end joints or beam-column joints, namely extremely low cycle fatigue. In this paper, thick walled un-stiffened box section steel piers subjected to incremental cyclic loading are analyzed by a three-dimensional elastic-plastic finite element analysis with shell and solid elements to investigate the behavior of local strain at weld toe. Several parameters, such as width thickness ratio, slenderness ratio, weld toe radius and axial loading, are taken into account. From engineering point of view, it is preferable to employ a simple parameter reflecting the local strain behavior. Here, the local strain is correlated to nominal strain, which is average strain along effective failure length by fiber model. Finally, a simple approach to extremely low cycle fatigue assessment is proposed and applied to test results.

Low cycle fatigue assessment for welded joints based on local strain approach Reviewed

Kazuo Tateishi, Takeshi Hanji, Tao Chen

The 60th Annual Assembly of International Institute of Welding page： XIII-2160-07 2007.6

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

As a method to predict fatigue strength of welded joints in extremely low cycle fatigue region, local strain based approach was discussed in this paper. Low cycle fatigue tests were conducted on T-shaped welded joints in order to find the crack initiation point and to obtain the fatigue life. On the other hand, local strain field around welded toe, where fatigue cracks were formed in fatigue tests, was analyzed by elasto-plastic finite element analysis, and the local strain amplitude at the cracking point was quantified. Based on the fatigue life obtained by fatigue test and the local strain amplitude by FEA, fatigue test results were compared with the low cycle fatigue strength curve, i.e., strain versus fatigue-life diagram. Test data were consistent with the strength curve. Consequently, it was demonstrated the fatigue assessment method based on local strain approach is available to predict the fatigue strength of welded joints even in extremely large strain region.

A prediction model for extremely low cycle fatigue strength of structural steel Reviewed

Kazuo Tateishi, Takeshi Hanji, Kuniaki Minami

International Journal of Fatigue Vol. 29 ( 5 ) page： 887-896 2007.5

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Miner's rule has been accepted as a simple and effective method for predicting the low cycle fatigue life under variable strain amplitude. However, in an extremely large strain field, corresponding to the fatigue life of less than 10 cycles, the accuracy of Miner's rule has not been verified. In this study, low cycle fatigue tests under variable strain amplitude in an extremely large strain field were conducted with a newly developed testing system. Miner's rule always predicted a longer fatigue life than the observed life. A simple model introducing the damage mechanics concept was proposed and its validity was examined as another method for predicting low cycle fatigue
life.

DOI： 10.1016/j.ijfatigue.2006.08.001

A new local strain based approach to low cycle fatigue assessment of welded joint Reviewed

Kazuo Tateishi, Tao Chen, Takeshi Hanji

Steel Construction Engineering, JSSC Vol. 13 ( 52 ) page： 73-81 2006.12

Language：English Publishing type：Research paper (scientific journal)

Several T-shaped welded joint models are analyzed by finite element method for low cycle fatigue assessment in this paper. Joint is subjected to random loading blocks and strain history is counted by range pair-range counting method. Endeavor is exerted to correlate local strain range of coarse FE model that ignores the weld toe profile with strain range obtained by fine material properties and loading pattern are also taken into account. After that, strain range factor while others' effects are insignificant. At last, proposed approach is introduced to the analysis of T shaped welded joint test. It turns out simple and convenient in low cycle fatigue assessment since cumbersome modeling of weld local profile becomes not necessary.

DOI： 10.11273/jssc1994.13.52_73

A prediction model for extremely low cycle fatigue strength of structural steel and welded material Reviewed

Kazuo Tateishi, Takeshi Hanji

The 59th Annual Assembly of International Institute of Welding page： XIII-2119-06 2006.7

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Miner's rule has been accepted as a simple and effective idea for predicting the low cycle fatigue life under variable strain amplitude. However, in an extremely large strain field, corresponding to the fatigue life of less than ten cycles, the accuracy of Miner's rule has not been verified. In this study, low cycle fatigue tests under variable strain amplitude in an extremely large strain field were conducted with a newly developed testing system. Since test results indicated that Miner's rule always predicted a longer fatigue life than the observed life, we proposed a modified life prediction model introducing the damage mechanics concept and investigated its validity.

Improvement of extremely low cycle fatigue strength of welded joints by TIG dressing Reviewed

Takeshi Hanji, Kazuo Tateishi, Kazuya Kitoh, Kuniaki Minami

Steel Construction Engineering, JSSC Vol. 13 ( 50 ) page： 27-34 2006.6

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

In order to prevent the low cycle fatigue damage in existing steel bridge members as observed in the Hanshin-Awaji Great Earthquake in 1995, improving the fatigue strength of welded joints can be a realistic option. In this study, the effect of TIG dressing, which is one of the ways to finish the weld toe, was investigated. As a specimen, T-shape welded joint specimens were employed. Some specimens were finished with TIG dressing, and the others were left as-welded. The low cycle fatigue tests were conducted for these specimens in the same conditions. The test results indicated that TIG dressing made the low cycle fatigue life of welded joints much longer.

DOI： 10.11273/jssc1994.13.50_27

Extremely low cycle fatigue assessment for welded joints based on peak strain approach Reviewed

Takeshi Hanji, Kazuo Tateishi, Kuniaki Minami, Kazuya Kitoh

Journal of Structural Mechanics and Earthquake Engineering, JSCE ( 808/I-74 ) page： 137-145 2006.1

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

As an estimation method of low cycle fatigue strength of welded joint in extremely large strain field, fatigue assessment method based on peak strain approach was verified. T-shape welded joints were employed for the low cycle fatigue test. The local strain field around welded portion and the peak strain at the cracked point was analyzed by elasto-plastic finite element method. The relationship between the peak strain and the fatigue life was consistent with the fatigue strength curve proposed by the authors. Consequently, it was demonstrated the fatigue assessment method based on peak strain approach was available even in extremely large strain region.

DOI： 10.2208/jsceja.62.101

Extremely low cycle fatigue assessment method for welded joint by peak strain approach

Takeshi Hanji, Kazuo Tateishi, Kazuya Kitoh

Proceedings of 6th Japanese-German Bridge Symposium page： CD-ROM 2005.8

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

As an estimation method of fatigue strength of welded joint in extremely low cycle fatigue region, peak strain based fatigue assessment method was verified. T-shape welded joints were employed for the verification test. The specimen was analyzed by elasto-plastic finite element method in order to quantify the local strain field around welded portion and the peak strain at the cracked point. On the other hand, fatigue life of the specimen was experimentally obtained by low cycle fatigue tests. The relationship between the peak strain and the fatigue life was consistent with the fatigue strength curve proposed by the authors. Consequently, it was demonstrated that the fatigue assessment method by peak strain approach was available even in extremely low cycle fatigue region.

A prediction model for extremely low cycle fatigue life under variable strain amplitude

Kazuo Tateishi, Takeshi Hanji

Proceedings of the 8th Japan-Korea Joint Seminar on Steel Bridges page： 251-257 2005.8

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Extensive experiments on low cycle fatigue for plain steel material have been conducted and obtained some important results. However there are few studies for extremely low cycle fatigue, corresponding to the strain more than 0.10.
In this study, a new low cycle fatigue testing system, in which a steel plate specimen was subjected to bending deformation and the image technique was introduced to measure the strains in the specimen, was developed. The testing system has enabled the low cycle fatigue test with introducing extremely large strains into the specimen. Low cycle fatigue tests on plain steel plates under constant and variable strain amplitude were conducted by using the system. Based on the test results, an estimation method for low cycle fatigue strength in extremely low cycle fatigue region was proposed.

Improvement of extremely low cycle fatigue strength of welded joints by TIG dressing

Kazuo Tateishi, Takeshi Hanji, Kazuya Kitoh

Proceedings of 6th Japanese-German Bridge Symposium page： CD-ROM 2005.8

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

The improvement of extremely low cycle fatigue strength of welded joints by TIG dressing was investigated. T-shape welded joint specimens of which weld toes were finished by TIG dressing were tested. The fatigue test results were compared with that of as-weld specimens tested in the same conditions. The test results indicated that TIG dressing could substantially increase the extremely low cycle fatigue strength of welded joints.

Low cycle fatigue testing system by means of image technique and its application to steel welded joints Reviewed

Takeshi Hanji, Kazuo Tateishi

Proceedings of the 1st International Conference on Advances in Experimental Structural Engineering page： 603-609 2005.7

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

A new low cycle fatigue testing system has been developed, in which a steel plate specimen is subjected to bending deformation, and strains of the specimen are measured by image technique. In this study, the low cycle fatigue tests of steel welded joints under constant and variable strain amplitude, particularly the fatigue life less than ten cycles in extremely large strain field, was conducted by using the newly developed testing system. On the basis of the test results, the applicability of low cycle fatigue life prediction model was confirmed, which has been developed for plain steel material, to welded portion, such as deposit metal and heat affected zone (HAZ).

Simple measuring method of surface profile of corroded steel plate by digital stereography Reviewed

Kazuo Tateishi, Kengo Shibata, Takeshi Hanji

Steel Construction Engineering, JSSC Vol. 12 ( 46 ) page： 27-34 2005.6

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

Surface profile of structural members sometimes gives valuable information to estimate mechanical behavior of existing structures. In this study, based on stereography technique, a simple method to measure the surface profile was developed, and apllied to a corroded steel plate surface. The method gave good results even for corroded steel plate surface which has few image patters and characteristics. The accuracy of the method was also discussed on the results for a variety of system conditions, such as camera position and camera resolution.

DOI： 10.11273/jssc1994.12.46_27

A prediction model for extremely low cycle fatigue strength of welded materials Reviewed

Kazuo Tateishi, Takeshi Hanji, Kazuya Kitoh, Kuniaki Minami

Journal of Structural Engineering, JSCE Vol. 51A page： 1275-1282 2005.3

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

We investigated the low cycle fatigue strength of welded materials under constant and variable strain amplitude in extremely large strain region. The test results indicated that fatigue strength of welded materials, particularly heat-affected zone (HAZ), was much lower than that of plain material. We then developed a model to predict the extremely low cycle fatigue strength of welded materials. Fatigue life estimated by this model was well agreed with test results.

Low cycle fatigue strength of butt-welded steel joint by means of new testing system with image technique Reviewed

Kazuo Tateishi, Takeshi Hanji

International Journal of Fatigue Vol. 26 ( 12 ) page： 1349-1356 2004.12

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

In this study, we investigated the low cycle fatigue strength of welded joints using a new fatigue testing system in which the image analysis technique was used to measure the strains in specimens. After checking the validity of the testing system, we used this new system to conduct fatigue tests on welded joint specimens. The test results indicate that the fatigue strength of welded material (weld deposit and heat affected zone) is much lower than that of the plain material.

DOI： 10.1016/j.ijfatigue.2004.03.016

Low cycle fatigue strength of welded joints in extreme large strain field Reviewed

Kazuo Tateishi, Takeshi Hanji

Proceedings of the 2nd International Conference on Bridge Maintenance, Safety, Management and Cost page： CD-ROM 2004.10

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Authors have developed a new low cycle fatigue testing method, in which a specimen is subjected to bending deformation and strain of the specimen is measured by image analysis. The advantage of this method is to be able to induce extreme large strain in steel plate even if it includes welding. In this study, the fatigue strength of welded joints in extreme large strain field was investigated by a newly developed testing system. The test results indicated that the fatigue strength of welded joints was much lower than that of plain material, and heat affected zone (HAZ) was the weakest spot.

A prediction model for extremely low cycle fatigue life under variable strain amplitude Reviewed

Kazuo Tateishi, Takeshi Hanji, Kuniaki Minami

Journal of Structural Mechanics and Earthquake Engineering, JSCE ( 773/I-69 ) page： 149-158 2004.10

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

For predicting the low cycle fatigue life under variable strain amplitude, Miner's rule has been accepted as a simple and effective idea. In extreme large strain field corresponding to the fatigue life of less than ten cycles, however, the accuracy of Miner's rule has not been verified yet. In this study, by means of a newly developed testing system, low cycle fatigue tests under variable strain amplitude in extreme large strain field was conducted. The test results showed Miner's rule always predicted longer fatigue life than actual life. As another idea for predicting low cycle fatigue life, we proposed a simple model introducing the damage mechanics concept and examined its validity.

DOI： 10.2208/jscej.2004.773_149

Low cycle fatigue strength of steel in extreme large strain field Reviewed

Kazuo Tateishi, Takeshi Hanji

Proceedings of the 3rd International Conference on Earthquake Engineering page： 561-565 2004.10

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Extensive experiments on the low cycle fatigue for plain steel material have been conducted and obtained some important results. There are few studies, however, on the low cycle fatigue in the extreme large strain field, corresponding to the fatigue life less than ten cycles.
In this study, we developed a new low cycle fatigue testing system, in which a specimen was subjected to bending deformation and the strain in the specimen was measured by image analysis technique. Low cycle fatigue tests on plain steel plates under constant and variable strain amplitude were conducted by using the testing system. Based on the test results, an estimation method for low cycle fatigue strength in the extreme large strain field was proposed.

A study on low cycle fatigue strength of welded joints by means of testing system with image analysis Reviewed

Kazuo Tateishi, Takeshi Hanji

Journal of Structural Mechanics and Earthquake Engineering, JSCE ( 752/I-66 ) page： 277-287 2004.1

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

Low cycle fatigue strength of welded joints was investigated by means of newly developed fatigue testing system in which image analysis technique was applied to measure the strain of specimens. It was validated that the strain measured by the image analysis was almost equal to measured value by strain gauge, and the low cycle fatigue strength of steel plate without welding was in good agreement with the results reported in former researches. After verifying the testing system, fatigue tests were carried out on welded joint specimens. The test results indicated that the low cycle fatigue strength of welded joints was much lower than that of plain material, and fatigue life was reduced by half.

DOI： 10.2208/jscej.2004.752_277

3-D shape measurement of corroded surface by using digital stereography Reviewed

Takeshi Hanji, Kazuo Tateishi, Kazuki Kitagawa

Proceedings of the 1st International Conference on Structural Health Monitoring and Intelligent Infrastructure page： 699-704 2003.11

A study on low cycle fatigue strength of butt welded joint by means of image analysis technique

Kazuo Tateishi, Takeshi Hanji

Proceedings of 5th Japanese-German Joint Symposium on Steel and Composite Bridges page： 405-409 2003.9

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Since Great Hanshin-Awaji Earthquake caused low cycle fatigue failures at base joints and beam-to-column connections in steel piers, it is important to investigate the low cycle fatigue strength of welded joints in civil structures. In this study, low cycle fatigue strength of welded joints was investigated by means of a new fatigue testing system in which image analysis technique was introduced to measure the strain of specimens. It was validated that the strains measured by the image analysis were almost equal to those by strain gauges, and the low cycle fatigue strength of plain steel plate was in good agreement with the result reported in the former studies. The low cycle fatigue tests carried out on welded joint specimens indicated that the fatigue strength of the welded joints was much lower than that of plain material.

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