نوع مقاله : پژوهشی
نویسندگان
1 دانشکده ی مهندسی عمران، دانشگاه صنعتی خواجه نصیرالدین طوسی
2 دانشکده ی مهندسی عمران - دانشگاه صنعتی خواجه نصیر الدین طوسی
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Generally, Rayleigh damping assumes a specified damping ratio for the structure
in the dynamic analysis. Although this assumption is accepted in analysis and
design of structures, there is some distance from the experimental results
showing that the damping ratio depends on the stress amplitude. In this paper,
the damping ratio for each element is a function of its principal stress and
its value is determined utilizing a proposed algorithm called Element Developed
Energy Dissipation Algorithm (EDEDA). The proposed algorithm was implemented into a code based on finite element, which is able to simulate nonlinear behavior of mass concrete utilizing the smeared crack approach. In this regard, due to stress redistribution in the nonlinear time history analysis, we have a
new concept, namely damping ratio redistribution such that when the stress
value of each element changes, the relevant damping value is updated. Based on
an analysis of a typical concrete gravity dam (Pine Flat dam), two usual methods in the Rayleigh damping approach which include stiffness proportional damping and mass/stiffness proportional damping are considered rigorously. In addition, the brittle damping approach was utilized in the proposed algorithm, where the damping contribution of a cracked element was eliminated from the computing procedure. It was found that when the damping redistribution was taken into account, the damping ratio in each element would be updated at each time step corresponding to the principal stress. This algorithm would produce more real results about the considered gravity dam so that in the low-level seismic excitation, the response of the structure was less than that in the traditional method and raising the excitation level led to higher damping affecting the crest displacement. In addition, the stiffness proportional damping leads to crack profiles in the neck region of the dam body showing more correspondence than the results obtained from the models with mass/stiffness proportional damping.
کلیدواژهها [English]
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