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<p>Being located in the central part of the Balkans, Republic of Macedonia has an economically strategic position for the region. Conditions of bridges are therefore significant in assessment of the entire seismic risk for the regional transportation network. This paper deals with vulnerability of road bridges typical for the Republic of Macedonia by use of an expanded multiple stripe analysis method approach. Typical bridges were selected based on an inventory study, which included statistical analyses of in situ collected data on all vital structures along the main roads and highways in the territory of the Republic of Macedonia. The results from the performed statistical analysis showed that most of these bridges represented reinforced concrete bridges with main girders. To define the vulnerability of these bridges, representative examples of variable geometrical characteristics were selected. Their values were adopted in combination with the values obtained from the statistical analysis. Vulnerability curves were obtained analytically by nonlinear dynamic analyses and use of different sets of ground motions scaled to different intensity levels. PGA was used as a measure of intensity. Based on nonlinear behaviour of the bridges and development of displacements in the bearings, four damage levels were defined. The soil-structure interaction was also taken into account in the analysis of the representative bridges. The seismic response of the typical reinforced concrete girder bridges was at an acceptable level.</p>

Following the M=6.4 earthquake that hit Durres in Albania on 26.11.2019, at the request of the Government of the Republic of Albania to the Government of R.N. Macedonia, in coordination with the deputy Prime Minister of the Government of R. N. Macedonia and the Director of the Bureau for Forensic Expertise of the R. N. Macedonia as operational coordinator, teams of experts were established for assistance and support to the local teams in rapid assessment on the structural safety of damaged buildings in the most affected areas. The Institute of Earthquake Engineering and Engineering Seismology -IZIIS (Ss. Cyril and Methodius University in Skopje) was leading the Macedonian mission with four teams composed of 11 experts. Most of the structures that were the subject of inspection were residential, mainly constructed as reinforced concrete structure and flat-slab systems prior the year 2000. Most of these structures suffered major nonstructural damage with negligible structural damages and extensive repairable structural damages. The cause of incurred damages was inconsistent application of recent knowledge in design, construction, and control of earthquake resistant structures. In order to define corresponding technical solutions for repair and strengthening, especially for the vital structures, it is necessary to take additional measures as detailed engineering inspection and science-based analysis.

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The proper seismic design of bridge structural bearings and expansion joints enables avoiding high repair costs after earthquakes. The paper discusses some experiences of the authors in design of bridge bearings and expansion joints according to Eurocodes. Within the scope of the detailed design of several new road overpasses, railway underpasses and railway bridges in the Republic of Macedonia, a special project on design of structural bearings and expansion joints has been realized. Based on the performed analyses, several issues are discussed. First, it has become evident that the geometry and the layout of the bridge structures have an influence on the layout and the fixation of the bearings (i.e., fixed, guided in one direction or bearings movable in all directions). The bridge shape in plane, the number of spans, the alignment disposition, etc. have also affected the adoption of bearing types and dimensions. Finally, the dynamic parameters and seismic behaviour of the bridges have appeared to be crucial in the design of the bearings. The paper also includes a comparison between design of bearings according to the Eurocodes and the Macedonian codes. For the purpose of comparative investigation of different layout solutions for the bearings' fixation, apart from static analyses, dynamic non-linear time-history analyses, using time-history ground acceleration records that correspond to the Eurocode 8 design spectra, have also been performed. From the analyses, the most superior layouts in terms of fixation, position and number of bearings have been obtained for each treated bridge structure. Precious experience has been gained during realization of the project. Since the Eurocodes' design philosophy has already moved toward development of new technologies for bearings, it is inevitable to make changes in the Macedonian practice. This philosophy has brought more freedom to the design process, especially in making decisions in obtaining optimum solutions depending on predominant actions, especially seismic ones.