François Voldoire

Prediction of Cracking in RC Walls Under Cyclic Loading by Means of a Novel Global Constitutive Model

In Reinforced Concrete (RC) structures, cracking is often a critical design parameter since engineering design codes limit the maximum crack opening to preserve the durability, tightness and aesthetics of RC buildings; robust and reliable crack opening computation methods are therefore necessary. For the case of large RC buildings (in particular for nuclear power plants), and specially for the case of cyclic (seismic) loadings, computational demanding finite element calculations are needed and so overall modeling is used. In this article, we propose to calculate the crack opening by means of a novel global (stress-resultant) nonlinear constitutive model for RC walls that incorporates crack opening as an internal variable. By means of an analytical averaging procedure and suitable physical hypotheses, four different local nonlinear phenomena are taken into account in the global model formulation [1]: (i) concrete cracking in two different crack directions and permitting both normal and tangential relative crack displacements; (ii) concrete stiffness reduction modeled by a scalar damage variable; (iii) steel-concrete slip and interface bond stresses, which are at the origin of the tension stiffening effect; and (iv) steel yielding localized at the cracks. The model is able to reproduce the behavior of RC plates submitted to in-plane and out-of-plane cyclic solicitations. Validation is provided by comparison with several experimental tests on RC structural elements, accounting for a large range of solicitations. Results show a good agreement both at global (force-displacement curves) and local (crack opening) levels. DOI 10.21012/FC9.105 Miquel Huguet et al.

DYNAMIC SOIL-STRUCTURE INTERACTION MODELING STRATEGIES APPLIED TO KASHIWAZAKI-KARIWA NUCLEAR POWER PLANT CASE-STUDY

On the framework of the French research project SINAPS@, the main goal of this work is to assess the impact of different soil-structure interaction modeling strategies on the Unit 7 Kashiwasaki-Kariwa Nuclear Power Plant reactor building response during the Niigata Chuetsu-Oki earthquake mainshock. his actual nuclear power plant case-study was already investigated during the KARISMA (KAshiwazaki-Kariwa Research Initiative for Seismic Margin Assessment) international benchmark exercise on 2009 organized by the IAEA (International Atomic Energy Agency) and OECD/NEA, which concluded on the difficulty to correctly predict the Unit 7 Reactor Building response during the mainshock by considering available standard soil-structure interaction modeling. The modeling strategies investigated in this work include soil non-linearity, by considering a cyclic critical state elastic-plastic model, and structuresoil-structure interaction influence by directly considering a simplified model of the adjacent Turbine Building. All numerical simulations are performed using code aster Open source software. The comparison of results with recorded signals within the Unit 7 Reactor Building allow to emphasize some conclusions about the role of modeling assumptions. This paper gathers the research work conducted by EDF R&D in the SINAPS@ task 4.3 during the years 2015-2016. 2330 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 2330-2342

SEISMIC EVALUATION OF EMBANKMENT-TYPE STRUCTURES WITH COUPLED HYDRO-MECHANICAL MODEL

The response of geotechnical structures under earthquake loading is highly nonlinear and often leads to problems of slope stability, foundation settlement and soil liquefaction. The prediction of these failure modes is a topic of great interest in geotechnical earthquake engineering, particularly for structural integrity assessment, which requires estimation of structural behavior during and after collapse. In this study, the earthquake response of a road embankment resting on a soil foundation is investigated. Both fully drained and coupled effective stress analysis are performed. Moreover, two different soil types are used for the embankment (looseto-medium and medium-to-dense sand). In the fully drained case, no failure of the embankment is observed for the medium-to-dense sand and for a certain level of ground motion. However, in the coupled effective stress simulation, for the same material and input motion, liquefaction of the foundation soil can lead to the generation of a thick shear band which produce large settlements and accelerate the failure of the embankment. The response of the loose-to-medium sand is fundamentally different, as several localization zones are generated, at the foundation part and inside the embankment body, as well. In both simulations fully drained and coupled effective stress analyis the embankment fail can occur due to shear band generation inside the embankment.