2002 Fiscal Year Final Research Report Summary
Intermediate-story Collapse of Reinforced Concrete Building Structures
| Project/Area Number |
12650582
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Building structures/materials
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| Research Institution | Tokyo Metropolitan University |
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Principal Investigator |
YOSHIMURA Manabu Tokyo Metropolitan Univ., Dept. of Arch., Graduate School of Eng., Prof., 大学院・工学研究科, 助手 (20210768)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAMURA Takaya Tokyo Metropolitan Univ., Dept. of Arch., Graduate School of Eng., Research Assoc., 大学院・工学研究科, 教授 (50305421)
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| Project Period (FY) |
2000 – 2002
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| Keywords | intermediate-story collapse / reinforced concrete columns / shear failure / loss of axial load carrying capacity / building designed by old code / seismic retrofit / earthquake response analysis |
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| Research Abstract |
During the 1995 Hyogoken-Nanbu earthquake, many concrete buildings suffered complete collapse at an intermediate story. Such collapse is believed to be due to that columns at a certain intermediate story underwent severe shear failure and eventually came to be unable to sustain axial load. To study this, shear-failing RC column specimens were tested. The specimens were laterally loaded until it came to be unable to sustain axial load. Axial load ratio and loading path were test parameters. The major findings are as follows:
1) Collapse occurs when shear force decreases to about zero.
2) Axial load level is decisive for the collapse behavior. Lateral drift and vertical deformation at the collapse were about 3 to 5% and 1% for axial stress of 0.27fc while they were about 10 to 20% and 2 to 5% for axial stress of 0.18fc.
3) Loading history has a significant effect on the collapse behavior including a failure mode.
4) A ration of vertical deformation increment vs. lateral drift increment increases as the loading proceeds.
When strong earthquakes occur in the future, many buildings designed according to the old code are very likely to suffer severe damages similar to intermediate-story collapse. Hence, they have to be retrofitted. Therefore, seismic drift demands of old buildings and those retrofitted using walls were analyzed and compared. Ten-story and five-story model buildings were studied. The major findings are as follows:
1) If old buildings are retrofitted in such manner that their base shear strength is more than or equal to 0.5 of the total weight, each inter-story drift demand remains within 1 % of the story height.
2) A slight difference in the strength of added walls may occasionally result in large difference in the drift demand.
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