HOW ARE THE EQUIVALENT DAMPING RATIOS MODIFIED BY NONLINEAR ENGINEERING DEMAND PARAMETERS?

Abstract eng:
When attempting to predict the seismic response of reinforced concrete (RC) structures, a trade-off has to be found out between a realistic representation of the dissipations through material behavior law and a numerically more efficient modeling with a controlled computational demand such as a Rayleigh-type damping model. Anyway, constitutive laws only describe internal dissipation and actually need a complementary dissipation term often chosen as a proportional damping matrix to take into account external dissipation sources such as interactions with the environment. Decoupling these two contributions in global dissipation measurement from experimental tests is still challenging. To address this problem, a numerical study based on an experimentally identified structural model is here presented. To this end, an experimental campaign has been carried out on RC beams set up on the AZALEE shaking table of the TAMARIS experimental facility operated by the French Alternative Energies and Atomic Energy Commission (CEA). In this paper, the experimental campaign is first presented. Secondly, a suited constitutive model is formulated and identified from the experimental results. Third, numerical dynamic experiments are carried out in order to assess the influence of several parameters on the energy dissipation and on the equivalent viscous damping ratio through two different methods. The validity of these results is assessed on a numerical case where a nonlinear model and an equivalent linear model are compared with each other. Experimental results of dynamic tests are also used as reference in order to estimate the additional viscous damping necessary to take into account the whole energy dissipation.

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