4 F. Léo et al. Stresses to concrete B1 at 100years Stresses in B1 and B2 > valid limit If No Yes One case stress before and after Stresses to concrete B2 at 100years Relaunch calculations Stresses in B1 and B2 > valid limit If No Yes Stresses to profile Step1 Step2 Step3 Step4 Step5 Step6 Fig. 1.2 Flowchart for computing the rupture stress 1.3 Results and Discussion 1.3.1 Crack Opening with First Reinforcement The fracture due to creep and relaxation effects have been discussed in this section. The applying force is 22 kN/m2 (breaking load of the beam when we do not use reinforcing steel taking up traction in concrete) at the serviceability limit state. The consideration of cracking of concrete under LUSAS is computed by using steel reinforcements. We therefore started by applying a very weak reinforcement, composed of 6 mm bars every 30 cm, in the longitudinal and transverse direction of the beam, on the upper face and on the lower face. Figure 1.3 presents the relationship between crack opening versus time for creep and shrinkage effects. It was observed that crack opening due to creep is significantly greater than that due to shrinkage. Indeed, at 100 years, creep represents 77.6% of cracking after loading and shrinkage only 22.4%. On the graph, we can notice that even at 100 years, the cracking induced by shrinkage continues to increase very slightly whereas it is completely stopped for creep. 1.3.2 Crack Opening with Second Reinforcement In order to decrease the impact of delay deformations on crack opening, the reinforcement has been increased. In this case, bars of 6 mm every 15 cm were placed on the upper side and bars of 12 mm every 15 cm on the lower side. Figure 1.4 presents the relationship between crack opening versus time for creep and shrinkage effects. This reinforcement of steel allows to remain below the admissible limit of cracking, because when we take into account cracking due to loading and delayed effects, we arrive at 0.08 mm at 100 years. Once again, we realize that the cracking due to creep is much greater than that due to shrinkage. The proportion remains the same since 77.6% of the cracking due to delayed effects comes from creep.
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