Low- and High-cycle Fatigue Behavior of Load-carrying Cruciform Joints with Incomplete Penetration and Strength Under-match

Takeshi Hanji,Kawin Saiprasertkit,Chitoshi Miki 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.4

The fatigue strengths of load-carrying cruciform joints with incomplete penetration and a strength mismatch between the base metal and the deposit metal were studied. Low- and high-cycle fatigue tests were performed on specimens with five matching conditions and two sizes of incomplete penetration. The test results revealed that the failure life was governed by crack propagation in both the low-cycle and high-cycle fatigue regions, and the crack propagation paths differed according to the matching and loading conditions. In addition, the fatigue strengths of the joints were compared for the degree of strength matching and the size of incomplete penetration in the low- and high-cycle fatigue regions. It was found that the effect of strength matching on the fatigue strength is negligible in the high-cycle fatigue region, but it becomes large in the low-cycle fatigue region and significantly reduces the fatigue life of the specimen in the under-matched joints.

Low Cycle Fatigue Assessments of Corner Welded Joints based on Local Strain Approach

Takeshi Hanji,박진은,Kazuo Tateishi 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.3

Low cycle fatigue strengths of corner welded joints with single bevel groove welding were studied. Low cycle fatigue testswere performed with three types of specimens which have different sizes of weld root face. The test results indicated that thelow cycle fatigue strength of the corner welded joints strongly depends on the weld root size. Then, the fatigue strength of thecorner joints was evaluated based on the effective notch strain at the weld root tip which was calculated by elasto-plastic finiteelement analyses. A unique relationship between the effective notch strain and the fatigue life of the joint was observedregardless of the weld root size. Therefore, it was revealed that the effective notch strain approach is applicable to evaluate thelow cycle fatigue strength of the corner welded joints.

Fatigue Crack Growth Characteristics of Several Kinds of Structural Steels Under Low-Cycle Fatigue Loading

Chao Jiang,Takeshi Hanji,Kazuo Tateishi,Masaru Shimizu 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.1

Because low-cycle fatigue is one of the failure modes in steel structures during earthquakes, crack growth prediction in the low-cycle fatigue region has become an important factor in the evaluation of the seismic performance of steel structures. This study conducted fatigue crack growth tests with several kinds of structural steels to clarify their crack growth behaviour in the low-cycle fatigue region. These tests employed an elastic compliance technique usually used in the high-cycle fatigue region to determine crack size. Before applying the elastic compliance method to a low-cycle fatigue crack growth test, a correlation between specimen load-line crack-opening elastic compliance and crack size was analytically derived. The test results indicated that crack sizes obtained by the elastic compliance method agree relatively well with those actually measured from images. Moreover, it was revealed that the crack growth rate can be correlated with the cyclic J-integral range calculated by finite element analysis, and that the relationships between the crack growth rate and the cyclic J-integral range are similar regardless of the steel type.

Local Strain-Based Low-Cycle Fatigue Assessment of Joint Structure in Steel Truss Bridges During Earthquakes

Chao Jiang,Takeshi Hanji,Kazuo Tateishi,Masaru Shimizu 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.5

During the 2011 Tohoku Earthquake, a truss bridge joint structure was cracked due to large cyclic deformation, making us recognize the importance of assessing the seismic performance of joint structures in truss bridges from the viewpoint of low-cycle fatigue. In this study, seismic response analysis of an actual deck truss bridge was performed under diff erent seismic waves, and local strain behavior generated at welded joints around a joint structure was clarifi ed using a zooming analysis technique. The results revealed the possibility that welded joints for a lateral gusset-plate in a joint structure can be cracking sites during earthquakes. In addition, it was indicated that seismic isolation bearings can signifi cantly reduce the local strain at the joint structure and improve its low-cycle fatigue performance. Moreover, as a simple countermeasure, weld toe treatment by grinding is also eff ective to decrease the possibility of low-cycle fatigue cracking at the joint structure.

Slip Coeffi cient and Ultimate Strength of High-Strength Bolted Friction Joints with Compact Bolt Spacing and Edge Distance

Shogo Kiyokawa,Kazuo Tateishi,Takeshi Hanji,Masaru Shimizu 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.4

In current design codes, the minimum bolt spacing and edge distance for high-strength bolted friction joints are specifi ed based on the bolt diameter, regardless of the plate thickness or steel strength. However, the mechanical performance of joints with a more compact bolt spacing than that given in the current design specifi cations has been little examined. In this study, the slip and ultimate strength of high-strength bolted joints with a compact bolt spacing and edge distance were investigated. Tensile tests were conducted on friction-type joints with various bolt arrangements. The use of a compact bolt arrangement was not observed to have a negative infl uence on the slip strength in these tests. The estimated strengths corresponding to the experimentally observed failure modes were found to agree fairly well with the experimental results within a 10% error. A parametric fi nite element analysis was also conducted to investigate the infl uence of the bolt arrangement on the slip coeffi cient. It was concluded that the bolt spacing and edge distance have little infl uence on the slip coeffi cient.

Effect of UHPFRC Overlay on Fatigue Cracks Propagating from U-rib Welds of Orthotropic Steel Decks

Masafumi Hattori,Kazuo Tateishi,Takeshi Hanji,Masaru Shimizu 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.6

Over the last decade, fatigue cracks have been observed at welded joints between U-ribs and deck plates in many orthotropic steel deck bridges in Japan. This paper focuses on fatigue cracks that initiate from a weld root of rib-to-deck welded joints and propagate to a deck plate. This study examines the eff ect of a countermeasure that uses overlaying Ultra-High Performance Fiber Reinforced cement-based Composites (UHPFRCs) on steel decks with cracks from U-rib welds, and confi rms the fatigue durability of this method. Specifi cally, the retardation of crack propagation and the fatigue durability of the UHPFRC itself as well as the interface between the UHPFRC and the deck plate were confi rmed by a wheel running test and fi nite element analysis. Based on the results, it was clarifi ed that this countermeasure has a positive eff ect on retarding further crack propagation compared with the method of overlaying steel fi ber reinforced concrete, which is generally adopted. In addition, it was revealed that the studied countermeasure has suffi cient fatigue durability.

Fatigue Strength Improvement of Weld Joints with Cope Hole

최성민,Kazuo Tateishi,Takeshi Hanji 한국강구조학회 2013 International Journal of Steel Structures Vol.13 No.4

Weld joint with a cope hole has relatively low fatigue strength, since high stress concentration is generated due to local sheardeformation inside the cope hole. In this study, fatigue strength improvement for the cope hole joint by burr grinding isinvestigated. I-section beams with cope holes, of which boxing weld toes were smoothly finished by burr grinding, were testedand analyzed in order to know the fatigue strength and the local stress behavior of the joint. Test and analysis resultsdemonstrated that the benefit of grinding on fatigue strength improvement is relatively small when shear stress is largely appliedto the cope hole detail.

Failure Probability for Fatigue Crack in Web Plate of Bridge Girder

Cut Atika Putri,Kazuo Tateishi,Masaru Shimizu,Takeshi Hanji 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.1

Out-of-plane gusset joints are commonly used in welded assembly structures such as bridges. The studies regarding outof- plane gusset joint often defi ne fatigue life of this joint as the condition when the crack has fully penetrated through the web plate. However, the time frame from crack initiation until reaching complete structural failure is unclear. In this study, extended fatigue crack propagation analysis of out-of-plane gusset joint is performed. The variation of infl uential parameters such as fl ank angle, weld toe radius, material constant, and the threshold value of stress intensity factor range was considered. The crack propagation analysis was done until the crack reaches 80% of the lower fl ange plate of the bridge girder. Since the crack propagation life is highly infl uenced by traffi c conditions, the probability distribution of the number of cycles and the crack width (2 b ) is presented in regards to the fatigue life ratio. In estimating the failure probability of the joint, the infl uence of human error to detect cracks during the inspection is considered. Five cases of the probability of crack detection are assumed to represent the capability of the inspector. It was found that bridge inspection and reparation of cracks are important in controlling the failure probability.

Evaluation of Thickness Effect on Fatigue Life Variation of Longitudinal Welded Gusset Joint

Cut Atika Putri,Tateishi Kazuo,Masaru Shimizu,Takeshi Hanji 한국강구조학회 2024 International Journal of Steel Structures Vol.24 No.2

Numerous studies have been conducted regarding the fatigue strength of longitudinal welded gusset joints. Most studies employed relatively small specimens. Thus, this study aims to evaluate the variation of fatigue life of longitudinal welded gusset joints by using the probabilistic fracture mechanics approach, particularly for larger specimens. Although some studies claimed that lower fatigue strength is found in the thicker main plate specimens, however only a limited number of fatigue test was conducted. A probabilistic approach was employed to conquer the shortfall. In this study, fatigue crack propagation analysis was performed on the main plate thicknesses of 12, 40, and 60 mm to evaluate the eff ect of main plate thickness on the fatigue life of the joints. Then, a probabilistic approach is given to investigate the variation of fatigue life of the joint. In addition, fatigue tests were carried out to investigate the crack propagation behavior on larger specimens. A signifi cant decrease in fatigue life was observed by the increase of the main plate thickness from 12 to 40 mm, however, no further decrease thereafter. The fatigue strength of longitudinal welded gusset joints with the main plate thickness of 12 mm was appertained to category F in the JSSC design curve. Meanwhile, the fatigue strength of longitudinal welded gusset joints with the main plate thickness of 40 and 60 mm falls into category G in JSSC. This condition was also confi rmed by the fatigue test results, where both specimens were classifi ed as category G in JSSC.