Local Scale Damping Model for Reinforced Concrete Elements

Abstract

Reinforced concrete (RC) structures dissipate energy when subjected to seismic excitations. Modeling seismic energy dissipations on a rational basis still represents challenging issues. At local scale, dissipative constitutive RC models are developed to take into consideration different phenomena, such as cracks opening, friction, plasticity, and their couplings or rebar bond slip. Practically some of those dissipative mechanisms are modeled by equivalent Rayleigh viscous damping at the global structural level. However, Rayleigh damping lacks a physical basis leading sometimes to an uncontrolled evolution of energy dissipation when non linearities occur [1]. This paper provides the basis of an updated local damping model based on parameters modeling concrete dissipative phenomenon, to reduce the need for arbitrary equivalent viscous damping as much as possible and thus better model energy dissipations on a rational physical basis. Using shake table experimental results on prismatic RC beams [2], a numerical study is presented to assess the performance of sixteen different global damping formulations to represent physical energy dissipation mechanisms. Energy balance analyses are used to evaluate dissipative phenomena at the local concrete level and to demonstrate that friction is the most significant local dissipative phenomenon. In addition, an equivalent viscous damping identification method is developed to determine transient damping ratio evolution during dynamic computations as a function of damage parameters, like stiffness degradation. An exponential function is found suitable to take into consideration global viscous damping adjustment as a function of local damage occurring during dynamic nonlinear analyses. COMPDYN 2021 8 th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering M. Papadrakakis, M. Fragiadakis (eds.