One- and Two-Dimensional Maximum Softening Indicators for Reinforced Concrete Structures under Seismic Excitation

The maximum softening concept is based on the variation of the vibrational periods of a structure during a seismic event. Maximum softening damage indicators, which measure the maximum relative stiffness reduction caused by stiffness and strength deterioration of the actual structure, are calculated for an equivalent linear structure with slowly varying stiffness characteristics. In the paper, a one dimensional scalar valued and a two-dimensional vector valued maximum softening damage indicator are defined. The one dimensional damage indicator, defined considering the variation in the first period of the structure, analogous to a SDOF system, is a genuine global damage index representing the average damage throughout the whole structure