Stress-Strain Law for Confined Concrete with Hardening or Softening Behavior

This paper provides a newgeneral stress-strain lawfor concrete confined by steel, fiber reinforced polymer (FRP), or fiber reinforced cementitious matrix (FRCM), obtained by a suitablemodification of the well-known Sargin’s curve for steel confined concrete.The proposed law is able to reproduce stress-strain curve of any shape, having both hardening or softening behavior, by using a single closed-form simple algebraic expression with constant coefficients. The coefficients are defined on the basis of the stress and the