The paper presents a study on the existing low-rise unreinforced masonry (URM) buildings constructed in the period from 1945 to 1980 in Serbia and neighbouring countries in the Balkans. Buildings of this typology experienced damage in a few earthquakes in the region, including the 2010 Kraljevo, Serbia earthquake and the 2020 Petrinja, Croatia earthquake. The focus of the study is a seismic design approach for Simple masonry buildings according to Eurocode 8, Part 1, which is based on the minimum requirements for the total wall area relative to the floor plan area, which is referred to as Wall Index (WI) in this paper. Although the intention of Eurocode 8 is to use WI for design of new buildings, the authors believe that it could be also used for seismic assessment of existing masonry buildings in pre- and post-earthquake situations. A study on 23 URM buildings damaged in the 2010 Kraljevo, Serbia earthquake has been presented to examine a relationship between the WI and the extent of earthquake damage. Seismic evaluation of a typical 3-storey URM building damaged in the 2010 earthquake was performed according to the requirements of seismic design codes from the former Yugoslavia and Eurocode 8.

Timber-concrete composite structures are innovative structural systems which have become the subject of extensive research and practical usage, primarily due to their attractive mechanical properties. This article deals with the experimental procedure and the analysis of the mechanical behavior of two different series of timber-concrete composite beams with the same span and geometry of cross-sections. In the first BF-series, the screws were used as a connecting system between the timber and concrete parts, whereas in the BN-series the combination of notches and screws, as a more complex system, was used for the same purpose. Both series were exposed to loading up to a failure by means of the standard four-point bending test. The mechanical behavior of the BF and BN-series beams was analyzed by a comparative analysis referring to: the correlation of the failure loading and the deflection, mechanisms of failure, the strain development across the height of mid-span’s and support’s cross-sections, the horizontal displacement in the timber-concrete interlayer at the support zones, the value of shear stresses and the calculated values of the effective bending stiffness of the beams. The differences in bearing capacity between both series of beams were negligible (about 5%), the effective bending stiffness of BF beams is lower for 32.86% compared to the BN-series and the average value of deflections in BF-series beams is twice as high than in the BN-series. The BN-series beams showed better mechanical behavior in aspects of development of shear stresses in support zones, exhibiting lower shear stress values with an average of 40%.

Starting with the premise that the choice of the optimal method for strengthening reinforced concrete (RC) structures is a complex task and that ferrocement strengthening is comparable to other advanced strengthening technologies due to its cost-effectiveness, ease of construction, and durability, this paper presents a comparative study of the flexural bearing capacity of RC beams strengthened with ferrocement strips applied by gluing. An overview of the life cycle assessment (LCA) based on embodied energy or CO₂ is presented in the introduction, based on the existing literature review. The research includes tests of 15 RC beams of identical cross-sections (150/250 mm) and a span of 3000 mm. Strengthening was conducted by applying four types of ferrocement strips (different widths and wire mesh layers). Two factors were examined: the verification of the comprehensive FEM numerical model against the experimental results and the applicability of existing simplified calculation methods for sufficiently accurate results which could be used in regular practice. The results show that the failure forces obtained from numerical models and experimental models differ by no more than 3.94%. The increase in the bearing capacity of the strengthened models is up to 21.4%. The transformed area method for the cracked section showed good results when compared to the FEM and experimental models. The analytically calculated failure force is contingent upon the partial factor for variable action, which was explored within the 1.5–1.7 range.

There is a significant building stock of post-WWII low- and mid-rise unreinforced masonry (URM) buildings in Serbia and the region (former Yugoslavia). Numerous buildings of this typology collapsed due to the devastating 1963 Skopje, Yugoslavia earthquake, causing fatalities, injuries, and property losses, as well as experienced damage in a few recent earthquakes in the region, including the 2010 Kraljevo, Serbia earthquake (M_W 5.5) and the 2020 Petrinja, Croatia earthquake (M 6.4). These buildings are three- to five-stories high, have clay brick masonry walls, and rigid floor slabs, usually with an RC ring beam at each floor level. This paper presents a case study of a URM building which was damaged due to the 2010 Kraljevo earthquake and subsequently retrofitted. A comparison of seismic analysis results, including the capacity/demand ratio and displacement/drift values, for the original and retrofitted building according to the seismic design and retrofit codes which were followed in Serbia as well as some of the neighboring countries for several decades and Eurocode 8 has been presented. The results of this study show that the selected retrofit solution that satisfied the Yugoslav seismic code requirements is not adequate according to the Eurocode 8, primarily due to significantly higher seismic demand.

Masonry has been widely used for the construction of residential buildings in Serbia and the majority of European countries. Confined masonry (CM) is a contemporary masonry technology that consists of load-bearing masonry walls enclosed in lightly reinforced horizontal and vertical reinforced concrete (RC) confining elements. CM has been widely used for the construction of low-rise and mid-rise residential buildings in Serbia and the region (Yugoslavia) since the 1960s. The design case study of a typical multi-family residential building located in Niš, Serbia (the third-largest urban center in the country), is discussed in this paper. This building was initially designed as a five-story CM structure in accordance with the 1981 Yugoslav seismic design code PTN-S, which was enforced in Serbia until 2019, when the Eurocode was adopted for official seismic design codes. Due to architectural constraints, the original design solution involving the CM system was not compliant with the code; hence, an alternative design using an RC-frame system with masonry infills was adopted. A comparison of two different design solutions provides insight into the different requirements of seismic design codes that have been used in the region. It is important to observe that seismic forces for RC structures determined in accordance with the PTN-S code are considerably lower compared to the ones determined according to EC 8-1, with the ratio ranging from 0.37 to 0.69. The seismic shear force according to Eurocode 8 is 1.46 times higher than the force that was used for seismic design according to the PTN-S code in the case of RC-frame structures. The results of an analysis of CM structures show that the seismic shear force in accordance with Eurocode 8 is almost 2.6 times higher than the force that was used for seismic design in accordance with the PTN-S code. The findings of this study are believed to be useful for understanding the difference in seismic design solutions for previous seismic design codes (which were used in the region for more than 40 years) and the present codes (Eurocodes).

Composite timber-concrete constructions are innovative structural systems which have become the subject of research and practical usage, primarily due to their attractive mechanical properties. This article deals with the experimental procedure and the analysis of the mechanical behavior of two different serious of timber-concrete composite beams. In the composite beams of the A series, screws were used as a fastening system in the interlayer between the timber and concrete parts, whereas in the B type series, a more complex system, the combination of notches and screws, was used for the same purpose. Both series were exposed to loading up to a fracture point by the means of the standard procedure (four point bending test). The mechanical behavior of the A and B-series beams was analyzed by a comparative analysis referring to: the correlation of the fracture loading and the deflection at the moment of fracture, forms and mechanisms of fracture, the development of dilatations at certain points of specific cross-sections, the displacement in the timber-concrete interlayer in the support zones, the value of shear stresses and the calculated values of the effective bending stiffness of the beams. The B-series beams where a more complex fastening system, as it was expected, showed a better mechanical behavior than the A-series beams.