Basic functions ·Compatibility: Es=8c Constitutive law: Constitutive law for steel bar When s,≤8y( s=EEs When &3 o=fy=const f E。E0Em Constitutive law for concrete Oc=f(8c)=AE08c A-k Plastic coefficient EeBasic functions • Compatibility: s c    • Constitutive law: Constitutive law for steel bar When s y    s Es s    When s y    f const  s  y  Constitutive law for concrete c c E c  f   0  ( )  E0 Ec   Plastic coefficient