A NEW GLOBAL MODEL FOR CRACKING IN RC WALLS AND SLABS UNDER SEISMIC LOADINGS

Abstract eng:
Nonlinear calculations of Reinforced Concrete (RC) buildings of Nuclear Power Plants (NPP) allow a better representation of their real structural behavior. The steel reinforcement design of these facilities and the seismic margin assessment of the existing ones are less conservative when considering the nonlinear behavior of RC structures. In this framework, the global cyclic constitutive model GLRC_HEGIS for RC walls and slabs is presented in this work. The developed model accounts for four different nonlinear physical phenomena: concrete cracking, concrete damage, steel-concrete slip and steel yielding. A fixed concrete crack pattern is considered in each finite element after cracking onset: crack orientation and spacing are determined by the stress state at the formation of the first crack. Concrete damage reproduces the loss of concrete stiffness when submitted to high stress. Reinforcement steel bars are supposed to yield at their intersection with cracks, where maximum steel stress is found due to the tension stiffening effect originated by the considered steel-concrete slip. The global stress-resultant model (which does not need multilayer modeling) is obtained by performing an analytical multi-scale analysis, accounting for in-plane efforts and out-of-plane bending moments. The implementation of GLRC_HEGIS in shell finite element models allows an efficient numerical computation of earthquake engineering applications of RC buildings, as pushover or transient dynamics analyses. GLRC_HEGIS model is applied to experimental tests on RC shear walls (CEOS.fr and SAFE programs) and to a transient dynamic analysis on the SMART benchmark mock-up representing a typical RC building of a nuclear facility. In addition of typical comparisons at the global scale (force-displacement curves), local comparisons are also shown since all the information relative to the considered physical phenomena, as steel plastic strain, steel-concrete slip, crack width or crack tangential slip, are obtained as a direct result of the finite element computation (they are internal variables of the constitutive model), see the following figure.

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