Damage characterization of the 1999 Athens Earthquake

On September 7, 1999 a strong earthquake with magnitude Mw=5.9, occurred close to the city of Athens in Greece. More than 80 buildings collapsed, about 150 deaths and hundreds of injuries were reported. A preliminary damage investigation was carried out by two of the authors in the most struck area. The most serious damages were observed at the northern suburbs of Athens, where the prevalent construction systems are reinforced concrete frames and masonry buildings. The hysteretic energy demands imposed on the RC buildings should have been quite high and not compatible with the structural systems and the inadequate construction details, but the overstrengths, redundancy and especially the presence of infill walls, contributed to a significant increase of the seismic capacity. In this way the survival of many buildings can be explained. The paper concerns some impressions gathered during the field visit about the observed damages, the construction typologies, the macroseismic intensities and other remarks based on some accelerometric, geological and seismological data today available. In particular the energy and displacement demands derived for the available strong motion data are analyzed and compared with the corresponding structural capacity of the typical existing RC buildings in the damaged areas. The comparison was performed by means of simulation of the dynamic nonlinear response of reinforced concrete frames with and without infill walls.