Standardized Multiapartment Blocks Built in Romania Before 1990: Seismic Design Levels Vs. Earthquake Performance

Abstract

An analysis of seismic force levels used in building design during the distinct periods of the pre-1990 evolution of Romanian codes is presented in the initial sections of the paper. The main changes introduced by each edition of the codes are considered in relation to the corresponding seismic macrozonation maps of the country. Seismic design forces are computed for 12 selected European building typologies, representative of the standardized, multiapartment blocks of flats built in Romania before 1990. These buildings, totaling hundreds of thousands of housing units, have withstood, so far, two to four strong earthquakes with moment magnitude, Mw, greater than 6. In a later section, the lateral resistance of the considered typologies is assessed analytically on the basis of ground motion records from the Vrancea earthquake (Mw = 7,1) on 30 August 1986, using a methodology proposed by the author and taking as reference the actual damage levels reported following the earthquake. By comparing the lateral resistances required to keep damage below these levels with the seismic forces used in design, the strength reserves mobilized during the earthquake are determined. The resulting large values can be explained by the inherent oversizing involved in standardization and also by some conservative design practices of the time.