Correlation Between Structural Performance Levels and Damage Indexes in Steel Frames Subjected to Earthquakes

Abstract. Various damage indexes have been introduced in recent years incorporating di erent parameters for estimating structural damage. Amongst these indexes, Plastic Ductility and Drift have been the center of attention of standards and building codes, like FEMA-356, because of their straightforward physical interpretation and ease of calculation. In this paper, several steel moment frames have been considered and their responses have been evaluated under a set of scaled earthquakes. A group of various damage indexes, which included cumulative and non cumulative, cyclic fatigue based, deformation based and modal parameter based, has been considered and the damage to structures has been evaluated on their basis. On the other hand, the performance levels of the frames have been estimated on the basis of the FEMA-356 standard. Based on these results, the correlation between FEMA performance levels and the values of damage indexes has been studied and some polynomial equations have been proposed. These simple equations can be used to estimate the value of the damage indexes from FEMA performance levels. Also, the range of each damage index for each FEMA performance level has been determined. At last, based on the concepts underlying each damage index, the indications of some important aspects of the structure response correlated to each FEMA performance level are investigated. Keywords: Seismic assessment; Structural damage index; FEMA-356; Performance levels