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A New Approach of Imaging Defects in Concrete Structures
Lee, Sanghun,Endo, Takao,Kagaya, Makoto,Sugawara, Takashi 한국방재학회 2012 한국방재학회 학술발표대회논문집 Vol.11 No.-
Image created by stack imaging spectral amplitudes based on the impact-echo (SIBIE) method is largely one-dimensional because a single frequency domain spectrum for wave reflected below a single point of impact is used to create the image. The method has limitations for representing defects in a cross section of a concrete structural element using two-dimensional coordinates. This study focused on defect detection and visualization in a concrete structural element using multiple impacts and accumulated SIBIE. An impactor was used to induce energy at multiple points at positioned at prescribed intervals along the structural element. A modified SIBIE method was applied to the collected data of each point and the modified SIBIE images were accumulated to generate one image (an accumulated SIBIE image). As a result, the defect positions could be represented in the cross section of the structural element using a two-dimensional coordinate system.
Detecting defects in concrete structures using accumulated SIBIE
Lee, Sanghun,Endo, Takao,Ishida, Hiroki 한국방재학회 2015 한국방재학회 학술발표대회논문집 Vol.14 No.-
Images created by stack imaging spectral amplitudes based on the impact-echo (SIBIE) method are largely one-dimensional because a single frequency domain spectrum for waves reflected below a single point of impact is used to create them. The method has limitations for representing defects in a cross section of a concrete structural element using two-dimensional coordinates. This study focused on defect detection and visualization in a concrete structural element using multiple impacts and accumulated SIBIE. An impactor was used to induce energy at multiple points positioned at prescribed intervals along the structural element. A modified SIBIE method was applied to the collected data for each point and the modified SIBIE images were accumulated to generate one image (an accumulated SIBIE image). As a result, the defect positions could be represented in the cross section of the structural element using a two-dimensional coordinate system. And the method appears to improve upon existing methods to detect voids or other defects in concrete.
Yasukazu Hijikata,Shigeo Ueda,Takao Yasuhara,Daisuke Umebayashi,Toshiki Endo,Toshihiro Takami,Masaki Mizuno,Kazutoshi Hida,Minoru Hoshimaru 대한척추신경외과학회 2022 Neurospine Vol.19 No.4
Objective: To assess the current management of primary spinal cord tumors (PSCTs) and determine whether and to what extent there are differences in surgical strategies for PSCTs. Methods: The Neurospinal Society of Japan conducted a survey between April 1 and 30, 2021. Certified spine surgeons were requested for information on the frequency of surgeries in 2020 and the surgical strategies adopted for each PSCTs. The following tumor histologies were focused: schwannoma, meningioma, and cauda equina tumor as extramedullary tumors; and ependymoma, hemangioblastoma, astrocytoma, and cavernoma as intramedullary tumors. The participants were divided according to their response as follows: experts, who had experienced ≥ 100 surgeries for PSCTs, and nonexperts. Results: Among 308 participants (63%), 35 (11%) were experts. The total number of PSCTs in 2020 was 802 of which 564 tumors were extramedullary and 223 were intramedullary. Schwannoma accounted for 53% of the extramedullary tumors, and ependymoma accounted for 39% of the intramedullary tumors. Surgical strategies significantly differed among both the experts and nonexperts groups. Some discrepancies in the adopted surgical strategies were observed between groups. Some of the nonexperts, and none of the experts, ruled out surgery for schwannomas (Eden type 4), astrocytomas, or cavernomas. Five nonexperts (2.2%), and none of the experts, resected the entire dura for meningiomas. Conclusion: A nationwide survey revealed that a sufficient consensus did not exist regarding surgical strategies for PSCTs. A disease-specific registry for PSCTs is necessary in academic societies.
Goto, Shintaro,Sakai, Toshikazu,Endo, Takao,Nagahara, Sabro 대한원격탐사학회 1996 International Symposium on Remote Sensing Vol.12 No.1
The effect of land use change (LUC) on the surface runoff were investigated by using the 1960's land use (LU) map and the 1980's LU map. The 1960's LU map was made by digitizing Agricultural Atlas by us and the 1980's LU map was made from 1987's NOAA-GVI data in southeast Asia. Firstly LUC area is selected by comparing the two LU maps. Secondly the change of surface runoff after and before LUC was estimated by using Fukushima and Suzuki (1986)'s model. Finally the relation between the change of surface runoff and the condition of soil erosion was discussed. Consequently the average surface runoff after drastic LUC between 1960's and 1980's was over two times more than 1960's. And the distribution of the drastic LUC area is almost same as the water erosion area. As a result, it was pointed out that the drastic LUC area was easy to be accepted by water erosion.
Application of Impact-Echo Method for Heterogeneous Materials
Sanghun LEE,Jun ABE,Shunsuke GOTO,Takao ENDO,TMitsuhiro TAKEDA,Masafumi KITATSUJI 한국방재학회 2014 한국방재학회 학술발표대회논문집 Vol.2014 No.-
Heterogeneous materials such as rock cannot be expected to have homogeneity so as to be used as structural materials. For example, in order to test large rocks more than one cubic meter, measures need to be taken against weaknesses such as internal cracks and fracture zones that can easily be overlooked in compressive strength tests. The impact-echo method could be available for evaluating strength and detecting internal defects in-situ concrete component with relatively good accuracy. In this study, measurements using the impact-echo method were carried for several types of rock specimens used at automobile crash safety tasting, and, by comparing the results with compression strength tests, the applicability of the impact-echo method for strength estimation of heterogeneous materials was evaluated.This work was supported by JSPS KAKENHI Grant Number 25420462.
이상훈,엔도타카오,이원철,Lee. Sang-Hun,Endo. Takao,Lee. Weon-Cheol 한국방재학회 2007 한국방재학회 학술발표대회논문집 Vol.2007 No.1
A continuing elevated bridge is replaced with mass-spring system model, and a part of the bridge is cut out as an analytical area. A viscous boundary is installed at both ends, and dynamic analyses are carried out changing the wave velocity of the viscous boundary, The result is compared with a result of a very long model corresponding to the solution with infinite length. A wave velocity is chosen so that the good performance of a viscous boundary is exhibited. The parametric analyses are carried out changing the model of various structural properties, and an approximation expression is suggested to obtain the wave velocity easily for setting a viscous boundary.
점성경계를 이용한 반무한 연속 고가교에 있어서의 지진동 계속시간이 지진응답에 미치는 영향
미우라다이키 ( Miura Daiki ),이상훈 ( Lee Sanghun ),엔도타카오 ( Endo Takao ) 한국구조물진단유지관리공학회 2018 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.22 No.2
When conducting the seismic response analysis on a long elevated structure, if the transmitting boundary is set at both ends of the analysis region, there is a condition that the response becomes larger than in the case of the free boundary. In this research, we studied the influence of the effective duration time of earthquake motion on the maximum displacement amplitude of earthquake response and the response energy of earthquake when carrying out similar analysis using viscous boundary. As a result, it was confirmed that the correlation between the effective duration and the relationship between the viscous boundary and the maximum displacement amplitude ratio of the free boundary is low. On the other hand, for the relationship between the effective duration time and the response energy ratio between the viscous boundary and the free boundary, the variance was small and a certain correlation was confirmed.
이상훈,엔도타카오,이시카와마사미,한연희,Lee. Sang-Hun,Endo. Takao,Ishikawa. Masami,Han. Yeon-Hee 한국방재학회 2008 한국방재학회 학술발표대회논문집 Vol.2008 No.1
Between traffic-induced vibration of a bridge and fatigue damage of its attached structures are very closely related. But any evaluation and design method considering the fatigue damage is not established yet. As an experimental method of evaluation of the fatigue durability, a method based on cumulative damage using a stress range histogram has been often used. However, to use the method, the fatigue durability of unmeasured points could not be evaluated. Then, in this paper, dynamic analysis of a sign frame on a bridge is carried out based on the vibration data of the bridge. And model optimization was performed for good agreement between measured responses and computed responses. As a result, we could get stress range histograms and calculate fatigue durability of unmeasured points.
이상훈,엔도타카오,카가야마코토,스가와라타케시,Lee. Sanghun,Endo. Takao,Kagaya. Makoto,Sugawara. Takashi 한국방재학회 2013 한국방재학회 학술발표대회논문집 Vol.2013 No.1
Image created by stack imaging spectral amplitudes based on the impact-echo (SIBIE) method is largely one-dimensional because a single frequency domain spectrum for wave reflected below a single point of impact is used to create the image. The method has limitations for representing defects in a cross section of a concrete structural element using two-dimensional coordinates. This study focused on defect detection and visualization in a concrete structural element using multiple impacts and accumulated SIBIE. An impactor was used to induce energy at multiple points at positioned at prescribed intervals along the structural element. A modified SIBIE method was applied to the collected data of each point and the modified SIBIE images were accumulated to generate one image (an accumulated SIBIE image). As a result, the defect positions could be represented in the cross section of the structural element using a two-dimensional coordinate system.