2002 Fiscal Year Final Research Report Summary
Importance Evaluation of Existing Road Bridges in Local Cities for Seismic Disaster Prevention taking account of Street-Blockade
| Project/Area Number |
13650524
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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 |
構造工学・地震工学
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| Research Institution | The University of Tokushima |
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Principal Investigator |
NARIYUKI Yoshifumi The University of Tokushima, Engineering, Associate Professor, 工学部, 助教授 (20127848)
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| Project Period (FY) |
2001 – 2002
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| Keywords | Street-blockade / Discreminant analysis / Mahalanobis' distance / Existing road bridge / Importance evaluation / Seismic disaster prevention / Local core city / Aerial photograph |
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| Research Abstract |
As a basic study on the order of priority of earthquake-resistant reinforcement of existing road bridges, in this study, an estimation method of street-blockade due to strong earthquake ground motion and an importance evaluation system of existing road bridges from the view point of seismic disaster prevention were investigated.
First street-blockade condition in Nagata-ward of Kobe City was visually investigated based on Aerial photographs taken within three days just after the 1995 Hyogoken-Nanbu earthquake. It became clear that the percentage of street-blockade was 32.5% there. Attributes of each link (street width, sidewalk width, angle between each link and tangent to fault line, number of roadside houses and collapsed house rate) were read from detailed housing map and distribution map of collapsed houses. From the result of the discriminant analyses based on Mahalanobis' generalized distance, in which criterion variable was existence of street-blockade of each link and prediction
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variables were the above-mentioned attributes of each link, it was found that accuracy was 86% and though the collapsed house rate contributed much to the accuracy, both angle between each link and tangent to fault line and number of roadside houses made few contributions to that.
Then the above-mentioned discriminant equation was incorporated into the system for evaluating the importance factor of existing road bridges in local cities. This extended system was applied to the central part of Tokushima City assuming that a near-field earthquake with a magnitude of 7.7 occurred at the eastern half segments of the Median Tectonic Line in the Shikoku Island. The percentages of collapsed houses and street-blockade in Tokushima City were 46% and 11.5% respectively. Each evaluation result is visually displayed on personal computer by using a simplified GIS.
From the evaluation results, it is shown that there is much effect of street-blockade and number of bridges retrofitted simultaneously on the importance of road bridges from the viewpoint of seismic disaster prevention. Less
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