SIMPLIFIED MODEL OF LOW-CYCLE FATIGUE FOR RC FRAMES

This note describes a simplified model of damage for reinforced concre te (RC) frame members. The model is different from those proposed in t he literature because it combines the concept of inelastic hinge and t he methods of fracture and continuum damage mechanics. The model allow s the characterization of the following effects: (1) unsymmetrical cro ss section with different yield capabilities at positive and negative bending; (2) influence of the axial force on the flexural member behav ior, stiffness, and strength degradation due to cracking of the concre te; (3) plastic deformations due to the yield of the reinforcement; an d (4) different stiffness under positive and negative flexure due to u nsymmetrical cracking even in symmetrical sections and low cycle fatig ue. The modeling of the low cycle fatigue effects, which is the main o bject of this note, is made using concepts from fracture mechanics. Nu merical simulations of tests reported in the literature validate the m odel.