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A modified energy-balance equation accounting for P-delta effects and hysteretic behavior of reinforced concrete members is derived. Reduced hysteretic properties of structural components due to combined stiffness and strength degradation and pinching effects, and hysteretic damping are taken into account in a simple manner by utilizing plastic energy and seismic input energy modification factors. Having a pre-selected yield mechanism, energy balance of structure in inelastic range is considered. P-delta effects are included in derived equation by adding the external work of gravity loads to the work of equivalent inertia forces and equating the total external work to the modified plastic energy. Earthquake energy input to multi degree of freedom (MDOF) system is approximated by using the modal energy-decomposition. Energy-based base shear coefficients are verified by means of both pushover analysis and nonlinear time history (NLTH) analysis of several RC frames having different number of stories. NLTH analyses of frames are performed by using the time histories of ten scaled ground motions compatible with elastic design acceleration spectrum and fulfilling duration/amplitude related requirements of Turkish Seismic Design Code. The observed correlation between energy-based base shear force coefficients and the average base shear force coefficients of NLTH analyses provides a reasonable confidence in estimation of nonlinear base shear force capacity of frames by using the derived equation. 相似文献
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S. Kelebek U. Demir O. Sahbaz A. Ucar M. Cinar C. Karaguzel B. Oteyaka 《International Journal of Mineral Processing》2008,88(3-4):65-71
The effects of dodecylamine (DDA), kerosene and pH on the recovery of combustible matter and ash content of a lignitic coal from Tuncbilek, Turkey have been studied using a three-variable and two-level (23) factorial experimental design. The coal sample responded favourably to batch flotation with high recoveries in excess of 95% using both kerosene and DDA respectively. The main effects of all three factors on the recovery are positive. Significance of DDA as a collector, is somewhat greater than that of kerosene, but its selectivity for ash reduction is not significant at the 95% confidence level. The pH-dependence of recovery by these collectors is opposite to each other. The DDA-induced flotation recovery is lowest at pH 9.4, an effect which has been related to precipitation of cationic species of this collector. The kerosene-induced recovery and grade of combustible matter increases with pH and this has been attributed to a better dispersion of coal and its associated clays. The two-way interaction effects are all negative at a smaller level. The main and interaction effects have been discussed on the basis of adsorption at most favourable surface sites, different modes of orientation of DDA species, competition with kerosene, and probable collecting properties of the frother used. The simultaneous effects of the two collectors on the recovery of combustible matter have been discussed at each pH value used. 相似文献
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Eren Ucar Eirik Keilegavlen Inga Berre Jan Martin Nordbotten 《Computational Geosciences》2018,22(4):993-1007
Simulating the deformation of fractured media requires the coupling of different models for the deformation of fractures and the formation surrounding them. We consider a cell-centered finite-volume approach, termed the multi-point stress approximation (MPSA) method, which is developed in order to discretize coupled flow and mechanical deformation in the subsurface. Within the MPSA framework, we consider fractures as co-dimension one inclusions in the domain, with the fracture surfaces represented as line pairs in 2D (face pairs in 3D) that displace relative to each other. Fracture deformation is coupled to that of the surrounding domain through internal boundary conditions. This approach is natural within the finite-volume framework, where tractions are defined on surfaces of the grid. The MPSA method is capable of modeling deformation, considering open and closed fractures with complex and nonlinear relationships governing the displacements and tractions at the fracture surfaces. We validate our proposed approach using both problems, for which analytical solutions are available, and more complex benchmark problems, including comparison with a finite-element discretization. 相似文献
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