Assessment of Seismic Capacity of Existing Buildings – Effects of Uncertainties

The seismic capacity of three buildings used as telecommunication centers in Greece is assessed based on design drawings that do not reflect accurately the “as built structure” and on limited information about the soil conditions. The buildings were designed under the old Greek codes for Earthquake Resistant Reinforced Concrete structures, already known to be quite inadequate both in the characterization of the seismic action and in providing sufficient strength and ductility to the structural members and the building as a whole. Steel telecommunication towers with several disk antennas had been added to the building roofs at later times. With limited knowledge about the type of soil at the building sites, the effect of soil flexibility was first examined in a parametric way and subsequently the assessment of the buildings' capacities was made on the basis of both elastic dynamic and inelastic static (pushover) analyses. For the latter analyses, the main uncertainty that was hereby addressed was the selection of a suitable horizontal load distribution. It was observed that different distribution may lead to different results regarding the buildings' capacity. However, in all cases examined, it was found that a drastic intervention would be needed to bring all three buildings up to current standards of increased seismic safety required by the new code for high importance telecommunication buildings that should stay operational during a strong, design level, earthquake.