| Project/Area Number |
08455210
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
構造工学・地震工学
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| Research Institution | HIROSHIMA UNIVERSITY |
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Principal Investigator |
SATOH Makoto HIROSHIMA UNIVERSITY,FACULTY OF ENGINEERING,ASSOCIATE PROFESSOR, 工学部, 助教授 (50034343)
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| Co-Investigator(Kenkyū-buntansha) |
ARIO Ichiro HIROSHIMA UNIVERSITY,FACULTY OF ENGINEERING,ASSISTANT, 工学部, 助手 (50249827)
IKICHAN Choy HIROSHIMA UNIVERSITY,FACULTY OF ENGINEERING,ASSISTANT, 工学部, 助手 (00284167)
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| Project Period (FY) |
1996 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥7,000,000 (Direct Cost: ¥7,000,000)
Fiscal Year 1997: ¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 1996: ¥4,300,000 (Direct Cost: ¥4,300,000)
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| Keywords | impact fracture / impact for brittle beam / dynamic shearing fracture / impact for RC beam / dynamic fracture process / dynamic photoelasticity / 脆性破壊 / 横衝撃 / 圧接鉄筋 / せん断力 / 脆性はり / 破壊へのせん断効果 |
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| Research Abstract |
Generally, the brittle fracture by a shearing force of structural members is a serious fracture phenomena because of its instant failure characteristics, In the Hanshin-Awaji Earthquake, there are many examples of this types of failures to such structures as reinforced concrete bridge piers. One of the important factors which the types of brittle fracture occur are the dynamic loads called earthquake shock acting to the structures as in the Hanshin-Awaji Earthquake.
The objective of this research is to study dynamic fracture process and mechanical characteristics of brittle fracture, and to clear the shearing effects in the fracture, The following results were obtained from the research.
1. On the mechanical characteristics of the fracture for brittle beam model subjected to lateral impact loads :
The dynamic photoelasticity method was applied to evaluate the crack propagation process and the dynamic states of stress of the epoxy beam model. An initial crack propagating from the lower edg
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e of the beam with a notch subjected to impact load is initiated by the flexural wave induced by the impact load. The crack propagates vertically to the beam axis when the impact point and the notch are same cross-section of the beam, but the crack changes the propagation direction towards the impact point or reverse direction when the impact point and the notch are not same cross-section. The reasons of the latter case are the effects of shearing stress due to the flexural wave propagation in the beam. The change of the crack propagation direction is governed by the magnitude of flexural stress in the beam when the crack propagates to the neutral axis and not by the impact position or the notch position. The crack propagation direction changes towards the part of beam growing larger flexural stress corresponding to the shear stress.
2. On the impact fracture properties of RC beam subjected to lateral impact :
The impact fracture experiments were carried out for the RC beam model by falling weight. In the experiment, two type of impact positions which were center span and 1/4 span of the beam were selected considering the shear force effects. In the case of 1/4 span of beam the fracture mode was a type of punching shear, and in the center span of beam the fracture mode was a type of plastic hinge. Also, in both types a few cracks were generated on the upper edge of the beam by the flexural wave propagation.
3. On the tensile strength of a pressure welded reinforcing bar
In the case that the pressure weld was done remaining a little oxidized surface, although the tensile strength of the bar was much the same with normally welded bar, the ductility of the bar decreased seriously and the brittle fracture occurred at welded surface. Less
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