Details of a Researcher - Kohiyama, Masayuki

Papers - Kohiyama, Masayuki

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Vulnerability Functions Using Seismic Diagnosis Data Extended by Equivalent Linear Models

Masashi SHIOMI and Masayuki KOHIYAMA

AIJ Journal of Technology and Design (Architectural Institute of Japan) 13 ( 26 ) 481-486 2007.12

Research paper (scientific journal), Joint Work, Accepted

It is important to establish an accurate vulnerability function to estimate seismic damage. The purpose of this study is to expand vulnerability functions of wooden buildings using seismic diagnosis data based on equivalent linear models. The vulnerability functions consider characteristics of the region such as ground and building characteristics. The paper describes a method to calculate ratio of building damage in a region. The accuracy of the method is verified using the damage data of the Great Hanshin-Awaji Earthquake Disaster.

Access to Document (DOI)

Questionnaire Survey on Effective Explanation of Seismic Capacity of Houses (Part 2. Effectiveness of Probability-Based Explanation)

Sasaki, K., and Kohiyama, M.

2nd International Conference on Urban Disaster Reduction (Disaster Management Society of Taiwan, National Science and Technology Center for Disaster Reduction, and National Taiwan University) 9 2007.11

Research paper (international conference proceedings), Joint Work

Effectiveness of probability-based explanation of seismic capacity was investigated based on a questionnaire survey. Dynamic analysis using a two-degree-of-freedom model of a wooden house was conducted to formulate a fragility curve. Then, probability of damage in a certain period was evaluated based on the fragility curve and a seismic hazard curve. An empirical formula of relation between JMA intensity and peak ground velocity was used to evaluate probability of damage under a certain seismic intensity.
About 55% of the respondents answered that probability of damage under a certain seismic intensity was the easiest among presented explanations of seismic capacity, and less than 10% of the respondents chose probability of damage within a certain period as the easiest explanation. In explaining several seismic capacities for comparison, showing only ratio or difference of the probabilities of damage was not as easy to understand as showing each probability value. The respondents had bias of overrated seismic risk first. But a house with high seismic capacity was preferred even after information on proper risk of seismic damage and additional cost to improve seismic capacity were provided. These results suggest that probability of damage is useful to explain seismic capacity of house.

Questionnaire Survey on Effective Explanation of Seismic Capacity of Houses (Part 1. Perceived Risk of Earthquake and Building Collapse)

Kohiyama, M., and Sasaki, K.

Research paper (international conference proceedings), Joint Work

The questionnaire survey was conducted to clarify effective explanation of seismic capacity of houses. The respondents were people who lived in Yokohama City, Kawasaki City or 23 Wards of Tokyo, who wanted home ownership for 20 to 30 years in future, and who were 30 to 49 years old, and 759 valid answers were obtained. Questions regarding seismic risk perception and preference of seismic capacity of a house were asked through a Web page from November 1 to 2, 2006.
It was observed that the respondents overrated seismic risk; about 60% of the respondents thought that they would experience strong ground motion of JMA intensity 7 in future and 85% thought a damaging earthquake would occur within 30 years in their or nearby town. In addition, the respondents underrated performance of a house with higher earthquake resistance grades. Risk of building collapse could be reduced to 1/5 by upgrading from Grade 1 to Grade 2 (1.25 times larger resisting force) and 1/10 from Grade 1 to Grade 3 (1.5 times larger resisting force). However, about 70% of the respondents did not think that the risk could be reduced to the above ratios. These results suggest that preference of seismic performance of a house can be changed by providing reliable risk information.

Effective Explanation of Grades of Seismic Capacity Using Probability of Damage

Sasaki, K. and Kohiyama, M.

Journal of Japan Association of Earthquake Engineering (Japan Association of Earthquake Engineering) 7 ( 6 ) 31-47 2007.11

Research paper (scientific journal), Joint Work, Accepted

The questionnaire survey was conducted to clarify effective explanation of grades of seismic capacity using probability of damage. The panels living in Yokohama City, Kawasaki City or 23 Wards of Tokyo who were in their thirties to forties, and who wanted home ownership were selected and 759 valid answers were obtained. Questions regarding seismic risk perception and preference of seismic capacity of a house were asked. As a result, it was observed that the panels overrated seismic risk and demanded various seismic capacities. Additionally, it was revealed that explanation using the probability of damage in relation to seismic intensity was effective, and that a house with high seismic capacity was preferred even after information on risk of seismic damage, which might remove the bias of the overrated seismic risk, and on additional cost to improve seismic capacity were provided.

Fundamental Study on Building-Elevator System for Reduction of Earthquake Damage to Main Rope

Asami MITSUI and Masayuki KOHIYAMA

Journal of Structural and Construction Engineering (Transactions of AIJ) (Architectural Institute of Japan) ( 621 ) 41-48 2007.11

Research paper (scientific journal), Joint Work, Accepted

Due to past several earthquakes, damage of elevators, especially in rope, were reported. It is quite important to maintain the function of an elevator for rescue activity after a severe earthquake. This study clarifies the correlation between vibration of a main rope of an elevator and the characteristics of a building (stiffness and damping factor). Influence of the setting position of a driving machine is also investigated. A model of a thirty-story building with elevator system is analyzed on vibration modes and dynamics responses to several seismic ground motions. It is shown that two-elevator system, which sets a transfer floor in the middle height of a building, can reduce the response of a main rope, and that increased damping factor can also reduce the response.

CONSIDERATION FOR PREPARATION OF PROPER PROPOSALS BY ACADEMIC SOCIETIES AND FOR THEIR IMPLEMENTATION

Kimiro MEGURO, Yasunori HADA, Hiroyoshi OSHIMA, Masayuki KOHIYAMA, Shinya KONDO, Mitsuaki SAEKI, Gaku SHOJI, Yoshiaki HISADA, and Miho Yoshimura OHARA

土木学会地震工学論文集 (Japan Society of Civil Engineers) 8 2007.08

Research paper (scientific journal), Joint Work, Accepted

本論文は，大都市圏の地震防災性の向上に資する従来よりも効率的で，かつ，より説得力のある提言を行うことを目的として，提言の施策への反映状況や既往の提言の文章表現や構造を分析した。具体的には，既往の提言の文章の表現や構造を詳細に分析し，提言の各文章を主語，述語，目的語に分類し検討を行った。また提言を社会に発信するまでの手続き(体制)についても，関連する学会を対象に調査した。最終的に，今後，学会が提言を行う際に参考となるポイントについてとりまとめ，地震防災性向上に資する提言のあるべき姿を示した。

Analysis on the Proposals for Earthquake Disaster Reduction by Academic Societies and Their Effects on the Society

Kimiro MEGURO, Yasunori HADA, Hiroyoshi OSHIMA, Masayuki KOHIYAMA, Shinya KONDO, Mitsuaki SAEKI, Gaku SHOJI, Yoshiaki HISADA, and Miho Yoshimura OHARA

土木学会地震工学論文集 (土木学会) 10 2007.08

Research paper (scientific journal), Joint Work, Accepted

本論文は，大都市圏の地震防災性の向上に資する従来よりも効率的で，かつ，より説得力のある提言のあり方を検討することを目的として，土木学会や建築学会が兵庫県南部地震の後に行った提言の分析と提言を取り巻く環境の分析を行った。具体的には，地震被害や地震防災対策の全体像に対する既往の関連学会の提言の位置づけと，対象としてきた課題の分野を明らかにし，これらの提言が社会に及ぼした影響や提言を取り巻く環境の変化を，研究発表，科学技術研究費補助金，国の防災関連予算，及び関連新聞記事等の変化から定量的に分析した。

Experimental Study on Indices to Detect Damage of RC Beam Based on Fourier Analysis of Response to Impact Excitation

Sano, A., Kumagai, Y., and Kohiyama, M.

Asia-Pacific Workshop on Structural Health Monitoring (Keio University) 395-403 2006.12

Research paper (international conference proceedings), Joint Work

Regarding damage detection of reinforced concrete (RC) structure using an impact hammer and a piezoelectric acceleration sensor, experiment and analysis were carried out to propose a reliable index to assess severity of damage to a member of RC structure. A test piece of a RC beam was used. First, the test piece was simply supported and two vertical downward forces were loaded monotonically to damage it. At some stage of damage severity, the test piece was moved out from the loading apparatus, and then was supported by urethane bearings. After that with an impact hammer, an impulse wave was given on the surface of the test piece in which downward forces were applied. The vibration (acceleration) of the normal direction of the surface was measured by the six accelerometers that were placed on the loaded and impact excited surface. Impact excitation was conducted at seven points. The above set of processes of loading (damaging) and measuring response to impact excitation was repeated until the test piece exhibited multiple visible cracks from the bottom to the top of the beam. The accelerograms were analyzed by the Fourier transform and some indices using not only the Fourier amplitude spectrum but also the Fourier phase spectrum were examined on the applicability for detecting damage.

Incentives and Disincentives to Retrofitting: Importance of Risk Communication in Programs of Earthquake Disaster Reduction

Masayuki KOHIYAMA, Miho YOSHIMURA, and Kimiro MEGURO

Journal of Environmental Engineering (Transactions of AIJ) (Architectual Institute of Japan) ( 606 ) 89-96 2006.08

Research paper (scientific journal), Joint Work, Accepted

For programs of earthquake disaster reduction, past studies have revealed that it is quite important not only to provide reliable risk information, but also to promote the communication with others for information exchange. The result of a questionnaire survey to homeowners supported this neighbors’ positive influence to retrofitting and also identified importance to provide engineering information on retrofitting plainly and to improve credibility of contractors of retrofitting work. Hence, interactive risk communication among homeowners, engineers and government officials is desired to assist comprehensive seismic risk management of homeowners. Based on the findings, programs to promote seismic risk management of houses are proposed from a viewpoint of effectiveness of risk communication.

Analysis on Strong Motion Indices Relevant to Damage of Two-Story Wooden Structures Based on Rank Correlation Coefficient

Masayuki KOHIYAMA

Journal of Structural and Construction Engineering (Transactions of AIJ) (Architectural Institute of Japan) ( 605 ) 55-62 2006.07

Research paper (scientific journal), Single Work, Accepted

Strong motion indices are analyzed on relevance to damage of two-story wooden structures. After nonlinear time history analyses of models with various stiffnesses for nine hundred input motions, a rank correlation coefficient are evaluated with respect to the relevance between intensity of an index and structural damage defined by a certain threshold of maximum story drift. It is clarified that the responses of linear single-degree-of-freedom systems with a particular elongated period and 20% damping ratio show fairly good correlation with the damages. It is observed that specific combinations of stiffnesses tend to disperse the damage, and consequently reduce the relevance.

Urban Damage Detection Using Remote Sensing Technology: Accelerating Response after a Severe Earthquake

KOHIYAMA MASAYUKI

Invited Lecture at National Center for Research on Earthquake Engineering, Taiwan 2006.06

Research paper (other academic), Single Work

Damage Estimation of Urban Houses Considering Seismic Performance and Urban Damage Detection Using Remote Sensing Technology

KOHIYAMA MASAYUKI

Invited Lecture at National Central University, Taiwan 2006.06

Research paper (other academic), Single Work

Correlation between Strong Motion Indices and Damage of Wooden Structures Based on Nonparametric Statistics

Kohiyama, M.

8th National Conference on Earthquake Engineering (100th Anniversary Earthquake Conference) (Earthquake Engineering Research Institute) 8 2006.04

Research paper (international conference proceedings), Single Work, Accepted

To propose more useful strong motion indices and to improve estimation accuracy of building damage, some strong motion indices (peak ground velocity, spectrum intensity, Japan Meteorological Agency seismic intensity, spectral displacement, etc.) are investigated with respect to correlation with damage of wooden structures. A nonparametric correlation coefficient, Spearman’s , is employed as an indicator of accuracy of damage estimation. Multiple input motions are used for nonlinear time history analysis of two-degree-of-freedom models of wooden structures, which have various combinations of story stiffnesses. As a damage model, maximum story drift angle is considered and three levels of threshold, 1/60, 1/30 and 1/15 rad are examined, which approximately correspond to minor, moderate, and major damage of a structure. Distributions of Spearman’s  of the strong motion indices are compared, and it is revealed that displacement response of a linear single-degree-of-freedom system with a damping ratio of 20% and with the elongated period that is determined by a damage threshold, shows fairly good correlation with the structural damage.

Image Fluctuation Model for Damage Detection Using Middle-Resolution Satellite Imagery

Kohiyama, M. and Yamazaki, F.

International Journal of Remote Sensing (Taylor & Francis) 26 ( 24 ) 5603-5627 2005.12

Research paper (scientific journal), Joint Work, Accepted

A damage detection method using middle-resolution satellite images, the Image Fluctuation Model method, is proposed, which employs a stochastic model of the digital number (DN) fluctuation in a normal condition and its significance test. The DN fluctuation model is formulated by considering an imaging process of a satellite sensor and an image registration process. A resulting thematic map is created based on a confidence level (12significance level), which is defined on a pixel-by-pixel basis as follows: the minimum significance level at which the null hypothesis, that the pixel DN can be considered as a sample of the DN fluctuation model, is rejected. The confidence level provides the model-based probability of ground surface change. The method is applied to the 2003 Bam, Iran earthquake using images acquired by Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) of Terra. The receiver operating characteristic curves of the method showed better detection performance than temporal image differencing or temporal image ratioing. Though the detection performance of building damage was not comparable to visual inspection on a building basis using high-resolution images of QuickBird, the confidence level map shows similarity at the district level to damage assessment results using high-resolution images.

Damage Detection for 2003 Bam, Iran, Earthquake Using Terra-ASTER Satellite Imagery

Kohiyama, M. and Yamazaki, F.

Earthquake Spectra (Earthquake Engineering Research Institute) 21 ( S1 ) S267-S274 2005.12

Research paper (scientific journal), Joint Work, Accepted

The damaged areas of the 2003 Bam, Iran, earthquake were detected using 15-meter-resolution satellite imagery acquired by Terra-ASTER. First, fluctuation of digital numbers was modeled as a normal random variable based on 17 pre-event images on a pixel-by-pixel basis. Then, the deviation value of each digital number in the post-event image was evaluated and converted into the confidence level, which indicates the possibility of an abnormal ground surface change. The detected damaged areas were verified with a highresolution satellite image and it was observed that the areas with earthquake influence were mostly identified. However, the pixels with significant change were induced not only from heavily damaged buildings but also dusty roads, possibly due to demolition work. It was suggested that prior knowledge like a high-resolution pre-event image would assist the interpretation of the detected result.

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A Study on the Structure of Resident Awareness about Retrofitting of Low Earthquake-Resistant Houses

Miho YOSHIMURA, Kimiro MEGURO, and Masayuki KOHIYAMA

土木学会地震工学論文集 (土木学会) ( 1 ) 10 2005.08

Research paper (scientific journal), Joint Work, Accepted

既存不適格住宅の耐震化の阻害要因は補強技術の問題，居住者の防災意識，家庭事情など多岐にわたる。需要に合致した耐震化推進策が必要である。関東地域の戸建住宅所有者を対象とし，補強工事に関する意識を調査した。家族構成・経済的状況・住宅状態などに応じ，耐震診断・補強関連情報の入手過程を把握した。補強工事の実施意欲に影響を与える要因を明らかにし，住宅所有者による自発的な耐震補強対策の誘導方法について検討した。

Analysis on Strong Motion Indices Relevant to Structural Damage Using Rank Correlation Coefficient

Masayuki KOHIYAMA and Fumio YAMAZAKI

Journal of Structural and Construction Engineering (Transactions of AIJ) (Architectural Institute of Japan) ( 594 ) 41-48 2005.08

Research paper (scientific journal), Joint Work, Accepted

This paper discusses the methods to compare the relationship between the strong motion indices and damage of structures. Based on the rank correlation analysis for the dynamic analysis results, it is pointed out that the correlations could change depending on the damage levels and the structural periods. In the nonlinear time history analyses, the responses of wooden structure models of Single-Degree-of-Freedom (SDOF) were simulated for nine hundred input motions. It is observed that the responses of the linear SDOF systems with 20% damping ratio and with elongated periods, considering the damage thresholds, show fairly good correlation with the damages.

Evaluation of Earthquake Disaster Mitigation Programs for Homeowners in Japan Based on Effective Risk Communication

Kohiyama, M., Kiremidjian, A.S., Meguro, K., and Yoshimura, M.

1st International Conference on Urban Disaster Reduction (Earthquake Engineering Research Institute and Institute of Social Safety Science) 8 2005.01

Research paper (international conference proceedings), Joint Work

Seismic risk management programs for homeowners in Japan are reviewed from a viewpoint of effectiveness of risk communication. Past studies have revealed that it is quite important not only to provide reliable risk information, but also to promote the communication with others for information exchange. In addition, a more effective approach would be based on collective behavior rather than expecting individual preparedness activities in Japan. To improve the risk communication and prompt the risk management action, a program of community-level retrofitting activities is proposed that would avoid fear of dishonest contractors, enhance interaction among homeowners exchanging information, and integrate retrofitting work of a single house into revival of urban areas addressing an inner city problem by group demolition and reconstruction.

Damage Detection from High-Resolution Satellite Images for the 2003 Boumerdes, Algeria Earthquake

Yamazaki, F., Kouchi, K., Matsuoka, M., Kohiyama, M., and Muraoka, N.

13th World Conference on Earthquake Engineering (International Association for Earthquake Engineering) 13 2004.08

Research paper (international conference proceedings), Joint Work

A strong earthquake of magnitude 6.8 struck the Mediterranean coast of Algeria on May 21, 2003 and the cities of Boumerdes and Zemmouri were most heavily damaged. QuickBird satellite observed these areas before and after the earthquake. Based on these images, the present authors performed visual damage detection of buildings. Using the post-event pan-sharpened image only, totally collapsed buildings, partially collapsed buildings, and buildings surrounded by debris were identified. Some buildings were difficult to judge their damage levels, and thus, the pre-event image was also employed as a reference to judge the damage status. By this visual inspection, a total 3,446 buildings were classified in Boumerdes and 1,399 buildings in Zemmouri based on their damage grades. The locations of refugee tents in the two post-event images were also identified. These observations indicate that high-resolution satellite images can provide quite useful information to emergency management after natural disasters.

Vulnerability Functions for Wooden Houses in Japan Based on Seismic Diagnosis Data

Kohiyama, M. and Yamazaki, F.

13th World Conference on Earthquake Engineering (International Association for Earthquake Engineering) 14 2004.08

Research paper (international conference proceedings), Joint Work

The regional difference of seismic capacity of wooden houses in Japan is revealed based on the seismic diagnosis data. The new vulnerability functions of wooden houses, which use the results of seismic diagnosis and an acceleration response spectrum, are proposed. They employ a probability density function of seismic performance indices of wooden houses, which are separated into an index of the resistance force and other indices regarding the degradation of resistance force. The input seismic motion is evaluated based on an acceleration response spectrum and natural periods determined by the indices of resistance force. The application results to the 1995 Hyogo-ken Nanbu earthquake are compared with the damage statistics at the five sites, which have seismic records. Though the proposed vulnerability functions are not based on the damage statistics, the estimated damage ratios coincide fairly well with the actual damage surveyed by local governments.

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