Shahrokh Ghavamian

Benchmarks for the validation of a non local damage model

ABSTRACT The aim of this contribution is to present a series of organised benchmarks that helps at validating the robustness of the FE implementation of a constitutive relation, its pertinence with respect to experiments, and quantitative and qualitative comparisons of structural elements. It is applied to an isotropic damage model used for concrete, coupled with a non local gradient formulation to avoid a spurious description of strain localisation. After the elementary (uniaxial monotonic, cyclic or triaxial loading) and structural (three point bending tests) simulations, an industrial application is presented in the form of a representative structural volume of a containment building for French nuclear power plants.

Damage mechanics applied to the seismic behavior of concrete structures

ABSTRACT The seismic behavior of reinforced concrete structures is generally evaluated through modal spectral approaches, based on linear elastic analysis. In the case of seismic reevaluation of existing structures using traditional methods, since the nonlinear behavior of materials is not taken into account, these techniques often lead to an overestimation of the needs in reinforcement. In this contribution, it is proposed to highlight how including nonlinearity in the mechanical behavior of concrete and steel can improve the seismic evaluation of RC structures. For this purpose, a pushover technique is applied on an office building. Contrary to a classical approach, the progression of the failure mode and the mechanical degradation can be obtained and used to accurately elaborate the best retrofitting strategy. Some improvements of the constitutive laws are nevertheless needed if the use of this type of approaches is to be extended to more complex structures. However, the maturity of most constitutive models is not enough to allow industrial applications.

Analyse du risque sismique pour les structures en béton armé élancées

ABSTRACT Hereafter, the seismic behaviour of slender reinforced concrete structures is studied. One can notice the significant influence of second order moments (also named P-Δ) particularly when material nonlinearity is present. These influences are governed by the geometry of the structure, material nonlinearities and seismic load intensity. A prospective analysis of these phenomena are presented in this work.