Simplified Model of Low Cycle Fatigue for RC Frames

This note describes a simplified model of damage for reinforced concrete (RC) frame members. The model is different from those proposed in the literature because it combines the concept of inelastic hinge and the methods of fracture and continuum damage mechanics. The model allows the characterization of the following effects: (1) unsymmetrical cross section with different yield capabilities at positive and negative bending; (2) influence of the axial force on the flexural member behavior, stiffness, and strength degradation due to cracking of the concrete; (3) plastic deformations due to the yield of the reinforcement; and (4) different stiffness under positive and negative flexure due to unsymmetrical cracking even in symmetrical sections and low cycle fatigue. The modeling of the low cycle fatigue effects, which is the main object of this note, is made using concepts from fracture mechanics. Numerical simulations of tests reported in the literature validate the model.