Developing a robust SHM method for offshore jacket platform using model updating and fuzzy logic system   总被引：1，自引：0，他引：1  

A. Mojtahedi  M.A. Lotfollahi Yaghin  Y. Hassanzadeh  M.M. Ettefagh  M.H. Aminfar  A.B. Aghdam 《Applied Ocean Research》2011,33(4):398-411

Structural monitoring is essential for ensuring the structural safety performance during the service life. The process is of paramount importance in case of the offshore jacket-type platforms due to the underwater structural parts subjected to the marine environmental conditions. This work is an experimental investigation on a laboratory model of a jacket platform with the objective of establishing a baseline finite element (FE) model for long-term structural health monitoring for this type of structures. A robust damage diagnosis system is also developed which is less sensitive to both the measurements and the modeling uncertainties. Experimental vibration tests are conducted on a physical platform model to obtain dynamic characteristics and then, the initial FE-model of the intact structure is developed to determine them numerically. Some differences between numerically and experimentally identified characteristics emerge due to various uncertainties in the FE-model and measured vibration data. To minimize these differences, initial FE-model is updated according to the experimental results. The updated FE-model is employed to predict the changes in the dynamic characteristics under variety of damage scenarios which are imposed by reducing the stiffness at the components of the model. Fuzzy logic system (FLS) and probabilistic analysis is developed for linguistic classification of damage and global damage diagnosis. Incorporation of the FLS fault isolation technique into FE-model updating method are proposed and evaluated for two different FLS methods to develop a vigorous damage diagnosis method. The efficiency of the technique is validated by different damage scenarios foreseen on the physical model. This technique is shown to be effective for diagnosing the presence of degradation and quantify it.  相似文献   

Mechanical and Physical Characterization of Tabriz Marls, Iran     

Ali Hooshmand  Mohammad H. Aminfar  Ebrahim Asghari  Hamid Ahmadi 《Geotechnical and Geological Engineering》2012,30(1):219-232

Three types of marls can be found in the Tabriz area (Iran): yellow, green, and gray/black marls. In the present paper, strength and deformation characteristics of Tabriz marls and their stress–strain behavior are investigated by various in situ and laboratory tests. In order to study the deformation behavior of these marls, various experiments such as the pressuremeter test, plate loading test (PLT), seismic wave velocity test, uniaxial compression test, standard penetration test (SPT), and direct shear test were carried out. Ranges of strain at the elastic and failure points were determined. Young’s and shear modulus were obtained. Test results showed that the strength characteristics increase with depth. The value of deformation modulus determined by the pressuremeter test was in good agreement with those obtained from the PLT. This implies that pressuremeter is a suitable in situ test for characterizing the deformation modulus of marl. Deformation modulus obtained from pressuremeter and plate loading tests were approximately 4–5 times the results of uniaxial compressive test and the deformation modulus obtained from seismic data was about 30–50 times the static deformation modulus. Stress–strain curves showed that the maximum value of strain at the elastic and failure points and the minimum value of strength and deformation modulus are corresponding to the yellow marls while the minimum value of strain and the maximum value of strength and deformation modulus are corresponding to the gray/black marls. Some empirical relationships between different characteristics of Tabriz marls were also derived.  相似文献   

A robust damage detection method developed for offshore jacket platforms using modified artificial immune system algorithm   总被引：1，自引：0，他引：1  

Mojtahedi  A.  Lotfollahi Yaghin  M.A.  Hassanzadeh  Y.  Abbasidoust  F.  Ettefagh  M.M.  Aminfar  M.H. 《中国海洋工程》2012,26(3):379-395

Steel jacket-type platforms are the common kind of the offshore structures and health monitoring is an important issue in their safety assessment.In the present study,a new damage detection method is adopted for this kind of structures and inspected experimentally by use of a laboratory model.The method is investigated for developing the robust damage detection technique which is less sensitive to both measurement and analytical model uncertainties.For this purpose,incorporation of the artificial immune system with weighted attributes(AISWA) method into finite element(FE) model updating is proposed and compared with other methods for exploring its effectiveness in damage identification.Based on mimicking immune recognition,noise simulation and attributes weighting,the method offers important advantages and has high success rates.Therefore,it is proposed as a suitable method for the detection of the failures in the large civil engineering structures with complicated structural geometry,such as the considered case study.  相似文献