Résumé:
A beam must have a ductile behavior to be able of supporting large deformations beyond its maximum load capacity. To ensure this behavior, a special attention should be given to construction requirements such as the rate of transverse reinforcement, the appropriate stirrup distribution, the rate of longitudinal reinforcement, the strength of concrete, the compressed concrete confinement, etc. In the same time, any type of brittle fracture should be avoided.
In this context, we developed an experimental research program. Validation tests of forty full-scale beams have been done in our Laboratory of Soil Mechanics and Structures (LMSS), taking into account the impact of different parameters. These tests allowed following, up to failure, the evolution of cracks and observing the different possible mechanisms. They also gave a lot of loading curves.
This also allowed evaluation of the bearing capacity of beams and the determination of the parameters that have a remarkable influence on the reinforced concrete beams and particularly on the increase of ductility. The stress-strain and the force-displacement curves derived from these tests have shown that the adequate spacing and the increase in the volumetric ratio of the transverse steel positively affect the confinement and increase the ductility of the beams. Also, the longitudinal reinforcement rate significantly improves the strength. A comparison of our test results with those of the literature was satisficing.
We also planned to conduct a simple numerical calculation, on a modified model, for the analysis of moment-curvature behavior of a shrunk-beam section to predict the curvature ductility. Determining the curvature requires knowing the compression zone of the beam section. Two methods were proposed: the first is an iterative one. The second method, so called method of possible cases, is proposed by Rezaie[ ] and helped us find exactly the position of the neutral axis. As a result, we saved a precious time of calculation. A comparison of the experimental test results with those derived from numerical modeling showed that the momentcurvature curves are encouraging and close to those of the reinforced concrete beams analysis under static loads.
