1990 Fiscal Year Final Research Report Summary
Fatigue Damage of Reinforced Concrete Beams
| Project/Area Number |
01550452
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Building structures/materials
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| Research Institution | Science Univ. of TOKYO |
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Principal Investigator |
NOMURA Seturo Science Univ. of Tokyo The Department of Science and Engineering Professor, 理工学部, 教授 (30096713)
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| Project Period (FY) |
1989 – 1990
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| Keywords | Reinforced Concrete / Cyclic Loading / Fatigue Damage / Accumulation of Plastic Strain |
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| Research Abstract |
In order to establish a method of seismic design based on ultimate strength concept for reinforced concrete (RC), it is important to grasp the deformation capacity beyond flexural yielding of RC members. But it is known that the deformation capacity of RC members is decreased evidently by cyclic loading. There are many points which are uncertain about damage under cyclic loading.
In this paper, Shear bending cyclic test of cantilever flexure beam is carried out in order to clarify the failure mechanism of RC members under cyclic loading. The experimental variables are shear span ratio and hysteresis of loading displacement. On the basis of the experiment, a few considerations are obtained.
(1) The axial strain and the lateral strain in hinge zone increase as the member absorbs energy.
(2) When the axial strain in hinge zone reaches maximum and begins to decrease, the rapid cyclic failure occurs.
(3) When the rapid cyclic failure occurs, the lateral strain in hinge zone begins to increase rapidly and value of lateral strain is about 4 - 5%.
According to these phenomena, we considered the cyclic failure mechanism as follows. Under cyclic loading, members absorb energy as plastic strain in hinge zone, and that brings into existence of vacant spaces in it. When the vacant spaces become large enough, members turn out not to be able to accumulate strain any more, and that causes the rapid cyclic failure. Here, we define such a failure as "strain accumulation failure on cyclic loading". This failure mode is caused by accumulation of plastic strain and that saturation.
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