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RISS 인기검색어
- 검색키워드
- 저자 : Norris Stubbs (검색결과 7 건)
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Nondestructive damage evaluation of deep beams
Dincal, Selcuk,Stubbs, Norris Techno-Press 2017 Structural monitoring and maintenance Vol.4 No.3
This paper presents a Level III damage evaluation methodology, which simultaneously, identifies the location, the extent, and the severity of stiffness damage in deep beams. Deep beams are structural elements with relatively high aspect (depth-to-length) ratios whose response are no longer based on the simplified Euler-Bernoulli theory. The proposed methodology is developed on the bases of the force-displacement relations of the Timoshenko beam theory and the concept of invariant stress resultants, which states that the net internal force existing at any cross-section of the beam is not affected by the inflicted damage, provided that the external loadings in the undamaged and damaged beams are identical. Irrespective of the aspect ratios, local changes in both the flexural and the shear stiffnesses of beam-type structures may be detected using the approach presented in this paper.
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Damage Detection in Jacket-Type Offshore Structures From Few Mode Shapes
Jeong-Tae Kim(김정태),Norris Stubbs(노리스 스텁스) 한국해양공학회 1994 韓國海洋工學會誌 Vol.8 No.1
본 연구에서는, 소수의 모드형상의 진동반응만이 측정된 자켓형 해양구조물에 존재하는 손상의 위치와 그 크기를 결정할 수 있는 알고리듬이 제시된다. 먼저, 모드형상의 변화로부터 직접 손상위치와 크기를 결정하는 이론이 제시된다. 다음으로, 세개의 진동모드형상이 측정된 자켓형 해양구조물의 수치예를 이용하여 알고리듬의 적합성이 예증된다. 본 연구의 결과는 다음과 같다. 첫째로, 자켓형 해양구조물에 존재하는 손상의 위치가 정확하게 예측되었다. 둘째로, 예측된 손상의 크기가 비교적 정확하게 예측되었다. An algorithm to locate and estimate severity of damage in jacket-type offshore structures for which modal responses are available for very few vibrational modes is presented. First, a theory of damage locaization and severity estimation(which yields information on the location and severity of damage directly from changes in mode shapes) is formulated. Next, the feasibility the damage detection algorithm is demonstrated by using a numerical example of an offshore jacket platform for which only three vibration modes are measured. Form the material presented here, two major results are observed. First, all damage locations in the offshore jacket platform are correctly predicted. Next, predicted damage is relatively correctly estimated.
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Nondestructive damage detection in structures using changes in compliance
Choi, Sanghyun,Park, Sooyong,Stubbs, Norris Elsevier 2005 International journal of solids and structures Vol.42 No.15
<P><B>Abstract</B></P><P>A methodology to identify damage in a structure is presented in this paper. The method utilizes a new form of damage index based on the changes in the distribution of the compliance of the structure due to damage. The changes in the compliance distribution are obtained using the mode shapes of the pre-damaged and the post-damaged state of the structure. The validity of the method is demonstrated using numerically generated data from beam structures and experimental data from a free–free beam structure with inflicted damage. In the numerical and experimental examples, the damage identification performance of the proposed method is compared with that of the existing strain-energy-based method. The results of the numerical and experimental studies indicate that the proposed compliance-based damage index method can be used in damage identification of the structure.</P>
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Improved parameter identification using additional spectral information
Nam, Dongho,Choi, Sanghyun,Park, Sooyong,Stubbs, Norris Elsevier 2005 International journal of solids and structures Vol.42 No.18
<P><B>Abstract</B></P><P>Spectral information such as natural frequencies from a frequency response function has been widely utilized in structural parameter identification problems. Recently the use of other information in the frequency response function, e.g., antiresonant frequencies, is getting attention. This paper presents application of additional spectral information such as antiresonant frequencies and static compliance dominant frequencies to structural parameter identification problems. The existing sensitivity-based system identification technique is extended by adopting the antiresonant frequencies and the static compliance dominant frequencies, and the performance of the approach using additional spectral information is compared with the approach using only natural frequencies via a numerical example of a mechanical system. The results of the numerical study indicate that the use of additional spectral information improves the accuracy in parameter identification.</P>
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Identification of the tensile force in high-tension bars using modal sensitivities
Park, Sooyong,Choi, Sanghyun,Oh, Soon-Taek,Stubbs, Norris,Song, Hwa-Cheol Elsevier 2006 International journal of solids and structures Vol.43 No.10
<P><B>Abstract</B></P><P>In certain field applications involving the repair or replacement of structural members, the knowledge of the tensile forces in tension members may be critical in the selection of the retrofit or rehabilitation process. To date, several methods have been presented to estimate in situ tensile forces using static and/or dynamic responses of the tension members. However, each and every one of these methods has its disadvantages as well as advantages in its procedures, level of accuracy, and equipment requirements. This paper presents a practical method to identify the tensile force in a high-tension bar using the changes in the modal sensitivities. The methodology can identify not only the tensile force but also other related parameters such as the magnitude of end constraint. The methodology utilizes the sensitivity relationship between the natural frequencies, the structural parameters, and the tensile force in the member. In this paper, the basic elements of the approach are summarized and the proposed method is validated using both numerical and experimental data. Also, the impact of model uncertainty to the performance of the parameter identification is investigated.</P>
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