Displacements of cracked members
The weakest section in a cracked member is obviously at the location of a crack. Away from a crack, the concrete in the tension zone is capable of resisting some tensile stress and thus contributing to the stiffness (the rigidity) of the member. Thus, the stiffness of a cracked member varies from a minimum value at the location of the crack to a maximum value midway between cracks. For calculation of displacements, a mean value of the flexibility of the member is employed.