The historic building of “Sokolski dom” in Kumanovo belongs to the plain masonry type of buildings. Built in the thirties of the last century for the needs of the “Sokolski Society”, this building was once the main impetus for enrichment of cultural, entertainment and sports life, enabling the proper development of many generations. Due to its significance it was put under the protection as cultural-historic heritage in the country. The subject of this paper is a detailed analysis of the stability of existing structure, which proved the need for its repair and seismic upgrading. With detailed analysis of the bearing and deformation capacity it was determined that the existing structure does not meet the requirements according to the national regulations. Therefore, the need for repair and strengthening was imposed, with the main goal of ensuring seismic stability of the building. Considering the possibilities and certain limitation for structural interventions from one hand, and the required bearing and deformation characteristics of the elements and the structure as whole from other hand, a traditional solution for strengthening was adopted, by reinforced concrete jackets and horizontal belt course. This technical solution provides increase of the structural bearing and deformation capacity of the system, as well as its ductility capacity, which is especially important for this type of buildings in case of seismic excitations. By increasing the deformation capacity, the input energy in the system would be consumed, which would greatly increase the seismic safety and security of the building.

The unexpected misbehavior of buildings during the recent frequent earthquakes in Mediterranean region resulted in significant loss of human lives, injuries and economic losses due to the poor capacity of their structural systems and built-in materials to sustain seismic load. Among the lessons learned from recent earthquake in southeastern Europe is that identifying existing buildings' vulnerability and thus reconsidering and improving their seismic safety, should become one of the top priorities for both, state and local government in seismic prone regions.

The potentially high vulnerability and poor performance of the existing buildings, after past seismic events, including exploitation period has raised awareness of the need to improve their seismic performance. Repair and strengthening gives new life to existing or ageing structures that might otherwise be demolished and replaced. This paper will address the issues related to repair and strengthening techniques for the first category building in Skopje, N Macedonia dated from 1924. Structural and nonstructural damages were observed due to the inappropriate foundation and maintenance of the building, which have increased during exploitation period and seismic actions. In order to define the stability of the building, non-destructive tests were applied for definition the material characteristics, further used in numerical analysis. Based on the performance assessment, retrofit schemes were proposed to address the main structural deficiencies and to meet national code requirements in N. Macedonia. The results of the overall investigations and analyzes for the capacity of the building are presented in this paper. Also summarized are the necessary structural interventions to ensure the necessary stability and reliability of the building for gravitational and seismic actions in accordance with the existing legislation in the Republic of North Macedonia. Since it is a first category, the dynamic response of the structure to real seismic actions, expected at site, is also considered according to the valid legislature which defines the assessment of seismic force considering local soil conditions. The outcomes from this project indicate the efficiency of the retrofit options utilized in reducing both the economic losses and collapse vulnerability of the building.

The impact of present building code requirements for seismic design of new buildings can readily be acknowledged, however applying regulation to existing buildings is an area less well defined. Presently, there is a diverse list of existing code references which could be interpreted to require seismic upgrades of existing structures. Unfortunately, these references do not provide a clear path toward addressing the hazards, evaluation and retrofitting of existing buildings. And when it comes to existing old buildings and monuments, constructed with low or no seismic consideration, the topic becomes much more complex and challenging. The problem of earthquake protection of historic buildings and monuments is radically different from that of other existing structures, due to the priority given to preservation of aesthetic, architectonic and historic values instead of keeping the structure operational. In providing the protection of these structures in a manner that requires the least intervention and the greatest care to preserve authenticity, the experts are permanently challenged by the fast development and the improved performance of new materials and techniques. This paper presents the integrated multidisciplinary approach to seismic protection of important structures that has been developed by the Institute of Earthquake Engineering and Engineering Seismology, IZIIS, Skopje, and implemented in the process of seismic upgrading or reconstruction of historic buildings and monuments in the country and beyond.

During the past earthquakes, we have witnessed extensive structural damage on modern highrise buildings. The use of flat-slab or partially flat-slab system, inadequate seismic dilatation joints, occurrence of plastic hinges in columns, short columns mechanism, building additional storeys on already designed/constructed structures, inadequate transverse reinforcement in columns and beams and so on. The solution to the problem is in implementing the most recent knowledge in analysis, design and construction. The Institute of Earthquake Engineering and Engineering Seismology has established a methodology to improve the current practice procedures, enabling analysis and design of robust and economical reinforced concrete structures with controlled and conducted ductile behaviour of elements and systems in general, up to ultimate limit states of the strength and deformability. The process of designing stable and economic structures is extremely complex, due to the necessary harmonization of a series of parameters related to the construction on one hand and its response to actual earthquakes on the other. The methodology and the dynamic response of real reinforced concrete buildings is presented here, through block diagrams and results from analysed examples. The reinforced concrete structures are designed with controlled and dictated ductile behaviour of the structural elements and the structure as a whole, for gravity/static loads and also for seismic/dynamic impacts that are expected for the defined location.