On the Relation Between Local and Global Damage Indices

Keywords: Seismic Risk Analysis, Global Damage Indices, Earthquake Resistant Design, Reliability Analysis, Earthquake Loads, Interstory Ductility, Structural Dynamics, and Earthquake Engineering.

Abstract: This study, based on the analysis of a database of structures subjected to simulated earthquake loads on a shaking table, shows that parameter-based global damage indices can be related to local stiffness degradation through operations of averaging over the body volume. The relationship obtained is applied to the case of numerical simulations of damage events as well as to the case of actual structures tested on shaking tables. Some results are also presented, relating parameter-based global damage indices to averages in space and in time of the local plastic strain. The relationship between local and global damage variables is also considered from an empirical point of view. A relationship between the apparent softening (global variable) of the structure and the interstory ductility (local variable) has been established. A set of fragility curves relative to structural limit states, have thus been defined.