| Project/Area Number |
59460133
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
土木構造
|
|---|
| Research Institution | Tokyo Institute of Technology |
|---|
Principal Investigator |
MIKI Chitoshi (1984, 1986) Associate Professor, Department of Civil Engineering, 工学部, 助教授 (20016645)
森 猛 (1985) 東京工業大学, 工学部, 助手
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
MORI Takeshi Research Associate, Department of Civil Engineering, 工学部, 助手 (10157860)
|
|---|
| Project Period (FY) |
1984 – 1986
|
| Project Status |
Completed (Fiscal Year 1986)
|
| Budget Amount *help |
¥4,900,000 (Direct Cost: ¥4,900,000)
Fiscal Year 1986: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1985: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1984: ¥2,400,000 (Direct Cost: ¥2,400,000)
|
|---|
| Keywords | welded bridge / fracture mechanics / stress ratio / weld defect / plate thickness / 疲労設計 / 疲労寿命 / 疲労強度 / 疲労亀裂 / 破壊力学 / 亀裂進展解析 / 応力比 |
|---|
| Research Abstract |
The effects of stress ratio, weld defect and plate thickness on the fatigue strengths of welded bridge components are studied, which should be considered in designing the bridges. This study is summarized as follows.
The effects of stress ratios on the fatigue crack growth in a high tensile residual stress field are examined. Specimens, made of 600Mpa class steel, are center-cracked type which contain longitudinal weld beads along the center of the plate. Fatigue crack growth rates and crack opening levels are measured at several stress stress ratios (-1 to 0.91). Under these test conditions, cracks fully open regardless of the value of stress ratio, and fatigue crack growth rates and threshold stress intensity factor ranges do not depend on the stress ratios.
Fatigue crack growth analysis using a fracture mechanics concept and fatigue tests are performed to quantitatively estimate the effect of weld defect (blowhole) size and shape on the fatigue strength of partially penetrated longitu
… More
dinal welded joints. In this analysis, a blowhole is regarded as a ellipsoidal cavity with small initial cracks along its wall. Number, interval, size and shape of initial cracks are determined by closely observed results on the fatigue crack initiation and propagation from the blowhole. The equivalent circular crack size for a blowhole is presented to predict fatigue life using a simplified approach. The predicted fatigue life is compared with experimental results.
The effects of plate thickness on the fatigue strengths of welded joints are studied. Fatigue tests are carried out for transverse fillet welded joints of various size with geometrically similar configurations and with same thickness rib plates. Fatigue crack growth analysis using fracture mechanics is also performed. The fatigue strengths of geometrically similar joints decrease with the increasing of the main plate thickness. However, the fatigue strengths of joints with same thickness rib plate do not depend on the main plate thickness when the plate thickness of rib plate is less than sixty percent of the main plate thickness. Less
|
