Issue 37

P. Bernardi et alii, Frattura ed Integrità Strutturale, 37 (2016) 15-21; DOI: 10.3221/IGF-ESIS.37.03 15 Focussed on Multiaxial Fatigue and Fracture Numerical simulation of early-age shrinkage effects on RC member deflections and cracking development P. Bernardi, R. Cerioni, E. Michelini, A. Sirico Dept. of Civil, Environmental, Land Management Engineering and Architecture, University of Parma (Italy) patrizia.bernardi@unipr.it, roberto.cerioni@unipr.it, elena.michelini@unipr.it, alice.sirico@studenti.unipr.it A BSTRACT . Shrinkage effects on short-term behavior of reinforced concrete elements are often neglected both in design code provisions and in numerical simulations. However, it is known that their influence on serviceability performance can be significant, especially in case of lightly-reinforced beams. As a matter of fact, the restraint provided by the reinforcement on concrete determines a reduction of the cracking load of the structural element, as well as an increase of its deflection. This paper deals with the modeling of early-age shrinkage effects in the field of smeared crack approaches. To this aim, an existing non-linear constitutive relation for cracked reinforced concrete elements is extended herein to include early-age concrete shrinkage. Careful verifications of the model are carried out by comparing numerical results with significant experimental data reported in technical literature, providing a good agreement both in terms of global and local behavior. K EYWORDS . Reinforced concrete; Shrinkage; Cracking; Short-term loading; Non-linear analysis; FEM. I NTRODUCTION n the design of reinforced concrete (RC) members, creep and shrinkage effects are usually taken into account for the evaluation of long-term deflections and pre-stress losses. It is indeed well known that these phenomena have a significant influence on the behavior of RC elements under sustained loads, by increasing their deformations and crack width over time. On the contrary, their effects on short-term response are often disregarded [1, 2]. Several theoretical and experimental works (among others, e.g. [3, 4]) have however pointed out that the restraining of concrete shrinkage (usually due to the presence of embedded reinforcement) significantly affects the cracking resistance of structural elements, as well as their deformations even under short-term loading. As a consequence, a proper numerical modelling should consider this effect, so as to avoid inaccurate predictions of structural performances at serviceability conditions. To this aim, concrete shrinkage can be explicitly considered by treating it as a prescribed deformation or as a fictitious force in the analyses [5-9]. In this work, an existing smeared-crack model for RC elements subjected to in-plane stresses, named 2D-PARC [10-12], is extended so as to correctly take into account early-age shrinkage effects. In more detail, concrete shrinkage is rigorously modelled by inserting it explicitly into 2D-PARC general algorithm as a prescribed deformation. The effectiveness of the proposed procedure is verified herein through the modelling of two experimental programs [13, 14] on RC shrunk beams with low reinforcement ratio tested to short-term bending. These elements are highly sensitive to shrinkage effects, especially in presence of a non-symmetric arrangement of steel reinforcement in the element cross-section. The restraint I