Dr. Ludovic Jason, SEMT, CEA DEN, Université Paris Saclay, F-91191 Gif sur Yvette, France

Biography: From 2004 till now, Dr. Ludovic Jason is Research Engineer at the French Sustainable Energies and Atomic Energy Commission (CEA), Saclay, France. He obtained his Phd thesis at Ecole Centrale de Nantes (France) in 2004 and his Accreditation to Supervise Research (HDR – highest French diploma) in 2016. From 2012 to 2018, he was deputy director of the Institute of Mechanical Sciences and Industrial Applications (IMSIA – CNRS-EDF-CEA-ENSTA laboratory). He is co-author of papers in international journals regarding the simulation of the mechanical behavior of large dimension civil engineering structures like containment buildings of nuclear power plants. His work is focused on the development of modelling strategies for civil engineering applications, including reinforced concrete constitutive laws, steel-concrete bond models, thermo-hygro-mechanical simulations for tightness estimation and scale changing methods.

Speech Title: Simulation of the active confinement in a steel-concrete bond model for reinforced concrete structures

Abstract: A numerical model to take into account the effect of the stress state on the bond behavior between steel and concrete in reinforced concrete structures is proposed. It is based on a zero thickness element, adapted to large-scale simulations and the use of 1D elements for steel bars. It supposes the definition of a bond stress – bond slip law which includes the confining pressure around the steel bar as a parameter. The implementation of the model is presented and the calibration of the bond law is discussed. A general equation is especially proposed. This evolution law is validated through the comparisons to 28 pullout tests. The model is able to reproduce the evolution of the bond stress (especially the bond strength) as a function of the confinement pressure, whatever the configuration (different concrete cover to steel diameter ratios). Finally, the consequences at the structural level are investigated on a reinforced concrete tie. The response for different confining pressures is especially studied. It shows the capability of the model to reproduce the “expected” tendencies with an increase of the initial elastic stiffness with increasing pressures and consequently a higher number of cracks in the stabilized nonlinear regime. The “transfer length” is also shown to decrease with increasing confining pressures.

Keywords: concrete structures, steel-concrete bond, confinement

Acknowledgements: The authors gratefully acknowledge the partial financial support from ENGIE for the development and the analysis of the simulation results.