Identification methods of material‐based damping for cracked reinforced concrete beam models

Abstract

AbstractSeismic performance evaluation in structural design requires the use of sophisticated numerical models. In particular, to accurately represent the non‐linear behaviour of reinforced concrete (RC) structures when subjected to dynamic loadings, the energy dissipation mechanisms must be accurately represented. However, the classical viscous damping models, which are still widely used, are not based on physical considerations at the material level and the choice of damping parameters is often arbitrary. This paper, thus, proposes a time‐domain damping identification method based on equivalent single‐degree‐of‐freedom (SDOF) systems. The methodology is developed using either an updated linear model or a non‐linear energy‐dissipating constitutive model. Energy dissipative phenomena are cracking, friction and unilateral effects upon crack closure. Both models allow the identification of different damping transient variations: (i) With the updated linear model, intrinsic damping ratios and frequencies are identified to define a simple generic damping model, and (ii) with the non‐linear constitutive model, the identified viscous damping ratios represent the dissipative phenomena not described by the material model. The aim is to propose simple models that can be used by anyone to complement their own models. Applying the method to experimental data allows evaluating effective damping ratio transient variations as functions of variables representative of non‐linear behaviour. It is shown that it is possible to accurately model the energy dissipation that is missing in the non‐linear dynamic constitutive models through effective viscous damping models based on dissipative phenomena internal variables.