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This paper uses theorem of shakedown to assess the shakedown limit of elastic–plastic offshore structures. For this aim, an envelope of elastic response of the structure to cyclic loading cases is required. The shakedown limit is basically a valid collapse mechanism and can be quantified using yield line analysis. In this work, Melan theorem of shakedown (lower bound) is employed. Requiring simple elastic envelope and the domain defining yield lines only are the advantages of the Melan theorem. The shakedown analysis can be conducted by the finite element method (FEM), which is the main body of this paper. In order to evaluate the method of this paper, which is in fact combining the Melan theorem and the FEM, two steel offshore frames are analyzed using the proposed method and the results obtained are compared with the results of classical non-linear analysis method. 相似文献
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In this paper, a formulation for shakedown analysis of elastic-plastic offshore structures under cyclic wave loading is presented. In this formulation, a fast numerical solution method is used, suitable for the Finite Element Method (FEM) analysis of large offshore structures on which shear effects in addition to bending and axial effects are taken into account. The Morison equation is adopted for converting the velocity and acceleration terms into resultant forces and it is extended to consider arbitrary orientations of the structural members. The theoretical methods of the shakedown analysis are discussed in detail and the formulation is applied to an offshore structure to verify the concept employed and its analytical capabilities. 相似文献
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The current study was carried out in order to investigate the short-term effect of different dilutions of wastewater on soil chemical properties, chemical fractions of zinc (Zn) and copper (Cu), and to assess the chemical buildup of heavy metal on two bean species. The experiment was performed as factorial based on completely randomized design with different dilutions of wastewater on two bean cultivars in two soil textures. The treatments consisted of irrigation with treated wastewater over all growing season, irrigation with wastewater and freshwater in equal proportions, and irrigation with well water only as control. The result showed that soil parameters are significantly affected by application of wastewater irrigation. Irrigation with wastewater increased the concentrations of organic matter, electrical conductivity, N, K, P, Fe, Cu, Zn, Mn, and Ni in soils compared to the control treatment. However, their values were all below international standards. Application of wastewater decreased soil pH and calcium carbonate equivalent. Plant tissue analysis showed increases in N, P, K, Zn, Cu, Zn, and Mn concentrations in grain and frond of beans in wastewater treatment as compared to the control. The concentrations of all elements in plants were lower than the toxic threshold. Chemical fractionations of Zn and Cu indicated that chemical forms of these metals were affected by irrigation with wastewater. Irrigating with wastewater resulted in the movement of Zn from the labile fractions towards the nonlabile fractions. In turn, mobility factor of Cu increased with application of wastewater. Maximum fresh and dry yields of beans were obtained from wastewater treatment compared to the control treatment. This study indicated that wastewater irrigation improves soil properties, plant growth, and yield without any contamination in soil and toxicity in plants. 相似文献
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H. Aliani S. BabaieKafaky A. Saffari S. M. Monavari 《International Journal of Environmental Science and Technology》2017,14(9):1999-2008
Identification of capacities for development of ecotourism is an undeniable priority in any country. For this purpose, various methods have been proposed by different researchers for locating regions with a potential for the development of ecotourism. These regions have different strong and weak points depending on the regional conditions. Evidently, the use of quantitative methods and reduced expert involvement in the process of decision-making and evaluation can yield better results. Therefore, in this research, a multi-criteria evaluation method based on fuzzy logic and network analysis process (ANP) has been used for the evaluation of the development of ecotourism. Therefore, one of the semi-northern regions of the country—Taleghan county, Alborz province—which has different capacities regarding ecotourism was chosen and investigated. Ecological and socio-economic criteria and indices were first identified and then quantified by fuzzy method, after which they were normalized. Further, the weight of factors was determined by the ANP method. Thereafter, using weight linear combination (WLC) operator, all the layers were combined and the region’s potential for ecotourism was zoned. The outcomes show that out of the entire area, 75.2% has different abilities for ecotourism development, while the remaining area lacks any special ability. Further, the results of the research indicate that the concurrent use of fuzzy logic and ANP method in determining the priority and weight of criteria provides more logical and flexible conditions compared to other methods for land evaluation in the context of the mentioned aim through WLC method. 相似文献
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Daryoushi Masoud Saffari Hamid Mahdavian Abbas 《Izvestiya Physics of the Solid Earth》2021,57(6):950-964
Izvestiya, Physics of the Solid Earth - ln this study, two relationships have been presented for predicting the significant duration values $$({{D}_{{s5 - 75}}}$$ and $${{D}_{{s5 - 95}}})~$$ of... 相似文献
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In the present paper, using action derivative with respect to Ricci scalar and its expansion relative to red-shift, to the second-order and consequently without needing dark energy, the history of cosmos expansion is reconstructed in vacuum. Then, employing supernova data, free parameters of the model which are the expansion coefficients, are calculated. It will be seen that if the free parameters of the model are zero, action of general relativity, which is a boundary mode of the gravity, is found. Also the cosmic age for this model in vacuum is calculated. Finally, it is attempted to reconstruct the reference action in terms of its Taylor expansion. Thus, it will be found that the reconstructed action and their actions definitely pass the Solar system tests. 相似文献
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Journal of Seismology - Earthquake is always known as a natural phenomenon with complex and unpredictable characteristics. One of the parameters which affects the ground motion properties is soil.... 相似文献
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Xie Wei Nie Wen Saffari Pooya Robledo Luis F. Descote Pierre-Yves Jian Wenbin 《Natural Hazards》2021,109(1):931-948
Natural Hazards - Landslide hazard assessment is critical for preventing and mitigating landslide disasters. The tuning of hyperparameters is of great importance to achieve better accuracy in a... 相似文献
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Journal of Seismology - 相似文献
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Performance-based seismic design(PBSD) aims to assess structures at different damage states. Since damage can be directly associated to displacements, seismic design with consideration of displacement seems to be logical. In this study, simple formulae to estimate the peak floor displacement patterns of eccentrically braced frames(EBFs) at different performance levels subjected to earthquake ground motions are proposed. These formulae are applicable in a PBSD and especially in direct displacement-based design(DDBD). Parametric study is conducted on a group of 30 EBFs under a set of 15 far field and near field accelerograms which they scaled to different amplitudes to adapt various performance levels. The results of thousands of nonlinear dynamic analyses of EBFs have been post-processed by nonlinear regression analysis in order to recognize the major parameters that influence the peak displacement pattern of these frames. Results show that suggested displacement patterns have relatively good agreement with those acquired by an exact nonlinear dynamic analysis. 相似文献
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