As part of the Mediterranean–transasian belt, the Croatian territory is characterized by a pronounced earthquake activity, with the strong ground motion occuring every 20 to 30 years. Although many buildings are designed in accordance with Eurocode 8 provision for earthquake resistant buildings, there is still a significant number of older buildings constructed without following any norms. The most detailed seismic tests are prescribed for so–called ''building without category'' to which they belong and school buildings and accordingly, the case study applied in this paper is 2D model of reinforced–concrete (RC) frame structure of primary school ''August Šenoa'' in Osijek. The primary school ''August Šenoa'' was designed in 70s of the last century in accordance with former Yugoslavian standards on technical conditions for design. The case study in this paper is based on seismic vulnerability assessment of low ductility reinforced–concrete 2D frame structures. For the seismic vulnerability assessment is used so– called ''State of the Art'' method, respectively nonlinear dynamic analysis of the incremental type (IDA) the numerical model of the building, whose configuration consists of RC frame. The interpretation of data obtained IDA analysis leads to the conclusion that these configurations (RC frames) are the most exposed to reaching the set limit state or, ultimately, cause construction collapse. In the implementation of IDA analysis, numerical model of RC frame is exposed to real time histories accelerogramms, or more precisely – the set of seven real time histories accelerogramms. There are four limit states of damage based on which damage states of RC frame structure are defined. Eventually, as a result of analytical resarch, IDA fragility curves and damage probability matrices for set of seven real time histories were defined.