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The durability of concrete structures, which are designed for long-term use is predominantly determined by the resistance to chemical influences, i.e., the concrete’s ability to protect the reinforcement steel. The carbonation and the chloride ingress into concrete are the most significant causes of steel corrosion and the potential failure of the structure. The primary goal is to ensure that any significant damage does not occur during the structure's service life, primarily achieved by selecting an adequate thickness of the concrete cover. The issue is approached through calculations based on performance analyses, and the use of appropriate models for these chemical phenomena. The paper provides a brief overview and the methodology for analysing the impact on the durability of concrete structures in accordance with the leading international normative documents. The emphasis is on the recent changes introduced in second generation of European Eurocode standards. The consequences of the analysed phenomena are presented through the results of field tests conducted at salt factories, coke industries, and thermal power plants, and through laboratory tests. The tests were performed in order to develop a rapid prediction method for the measure of chloride ingress into concrete without the stimulating chloride ion migration by electricity, as an alternative to standardized tests.

Textile-reinforced concrete (TRC) is a reinforced concrete, where steel reinforcement is replaced with textiles or fibers. Textile reinforcement is a material consisting of natural or synthetic singular technical fibres processed into yarns or rovings which are woven into multi-axial textile fabrics having an open mesh or grid structure. In the paper an overview of tests results related to mechanical properties, deformation properties and durability characteristics of textile meshs are presented. Applications of different textiles as reinforcement in TRC is analyzed through some realized projects. TRC has been successfully employed for strengthening or repair of damaged structural elements and lightweight, thin structural elements (precast thin-walled elements, shells, tanks, pipes, pedestrian bridge, waterproofing structure, integrated cladding systems, external insulation system).

Research at faculties in Serbia after WWII, even though they were fruit of individual efforts, resulted in significant theoretical contributions. Organized, mostly applied research was conducted within institutes with participation of scholars and researchers of the faculties. Since 1952, the Association of Yugoslav Laboratories (AYL) consolidated the research, thus providing a considerable contribution to the structural engineering in Serbia. This contribution in the field of theory and practice was the basis for the notable achievements that glorified our structural engineering worldwide. Theoretical contributions contained in the doctoral dissertations in the field of Theory of structures and Geotechnics are significant, so they were listed in the paper. Majority of these studies became a part of research project as late as in 1976, and they are briefly presented in the paper. The synthesis of project results from fundamental and technological development research was published in numerous monographs, articles, papers and proceedings of scientific and professional meetings and some of them are commented in this paper. The necessity to introduce technical regulations which have already been adopted in the EU countries EN 1990 to 1999, i.e. the Eurocode, was emphasized. There is a brief discussion of several research directions which are topical nationwide as well as worldwide.

Safety and functionality of concrete road bridges are of a special importance for the traffic flow continuity in different circumstances including after earthquakes, floods, as well as after vessel or vehicle impact on piers. This is why almost all countries use Bridge Management Systems (BMS). They include the bridge inspection manuals, guidelines, report writing, bridge condition evaluation and determination of priorities (rating) for maintenance work or rehabilitation to achieve the design service life of bridges. This paper presents a comparative analysis of some documents of certain countries and associations, related to BMSs and their main components.

Built heritage is incessantly exposed to natural disasters including numerous earthquakes. Therefore, it is important to take measures to reduce vulnerability and increase the protection of buildings depending on the exposure to seismic hazard and the importance of the building. Studying the history of construction reveals examples of building constructions aimed at protecting against earthquakes. For this reason, such examples are presented here, starting with the buildings from the distant past until now. The documentation related to the action of earthquakes throughout history and the procedures in planning the building protection measures in order to preserve the heritage from dilapidation were commented. The paper, also, presents some examples of incorrect use of materials and construction technologies that damage the original structural fabric, and thus, the value of a certain cultural property.

The double strap joint splicing of glass fiber reinforced polymer (GFRP) bars for reinforced concrete (RC) beams strengthening, applying the near surface mounting (NSM) method, has been proposed in the paper. The proposed method consists of application of the supplementary GFRP bars symmetrically positioned in the cut-off zone of the main GFRP reinforcement. The performances of this splicing method have been experimentally tested for the most unfavorable case of the GFRP reinforcement cut-off in the maximal bending moment zones. During the experiment, the varied parameter has been overlapping length of the bars, taking values of 20Ø and 40Ø. Evaluation of the splicing technique is done comparing the experimental results with the results of the behavior of beams strengthened by GFRP bars without cut-off and with cut-off, but without splicing. Experimental research encompassed analysis of strength, stiffness, ductility, crack pattern, strains in the steel, GFRP reinforcement and concrete, and the failure modes of the beams. It has been shown that in case of the cut-off of the GFRP bar, strengthening effectivity decreases for 39%, and that in the case of bypassing the cut-off using double strap 20Ø and 40Ø long, strengthening effectivity decreased 23%, and 14% respectively, compared to the beam without GFRP bar cut-off. Using extrapolation, it has been shown that double strap with length of 60Ø provided strength equivalent to the case without cut-off. The result of application of this splicing method of the additional GFRP bars is significant increase of strength and serviceability of the strengthened RC beams. [ABSTRACT FROM AUTHOR]

This article examines the structural integrity of the pre-stressed concrete dome of Belgrade fair hall 1, which is the largest of its kind in the world. The analysis is conducted using numerical simulation and finite element analysis, and the results show extreme values at critical locations within the model. The article also discusses the application of a concrete pre-stressing system called IMS-¿e¿elj in the construction of the dome, which is considered a prominent example of this system worldwide. The findings provide valuable insights into the construction and maintenance of large concrete structures. [Extracted from the article]

Comparative non-linear static (NSA) and non-linear dynamic analyses (NDA) of 2D frames (as parts of skeletal 3D structures) of RC buildings founded on piles are presented in this paper. In order to produce a more realistic presentation of behaviour of a frame structure, the analysis involves a structure-foundation-soil interaction. Also, the model involves a linear-non-linear dynamic pile-soil interaction, using link elements. The foundation consists of drilled piles having 60 cm in diameter. The soil is modelled using Multi-linear plastic link elements, as well as with p-y curves, on both sides of the pile, assuming that p-y curves transfer only compression (p-y curves are experimentally determined non-linear relationships of displacement/pressure in soil, along the depth of a pile). The analysis shows the problems which accompany extraction of a 2D frame, as a representative of a regular 3D space frame. The impact of onset and location of individual plastic hinges on seismic performances of the analyzed structural system are investigated, and relative floor drifts are analyzed. It was concluded that the analysis of 2D frame, in the interaction with the foundation and soil, may provide sufficiently accurate results of behaviour and assessments of seismic performances of skeletal RC multi-storey building. It is important, because introduction of a spatial structure in such analyses is very complex and challenging.

In this paper two different methods of selection and scaling ground motion data were investigated in order to examine their effect on accuracy predicting seismic response of RC bridge. First method used is one proposed in EN 1998-2 and second method is scaling of earthquakes based on calculated conditional mean spectrum (CSM) related known parameters of earthquake scenario for certain location. For both methods certain limitations upon scaling factor were implemented in order to examine its effect on accuracy. Totally 4 sets consisted of 7 records were selected, and average seismic response were obtained from nonlinear dynamic analysis. Responses were compared to calculated real response of bridge, so called point of comparison. Conclusions were made about investigated methods accuracy and effect on imposed limitation of scaling factor on realistic prediction of seismic bridge response.

Nonlinear static analysis, known as a pushover method (NSPA) is oftenly used to study the behaviour of a bridge structure under the seismic action. It is shown that the Equivalent Linearization Method - ELM, recommended in FEMA 440, is appropriate for the response analysis of the bridge columns, with different geometric characteristics, quantity and distribution of steel reinforcement. The subject of analysis is a bridge structure with a carriageway plate - a continuous beam with three spans, with the 24 + 40 + 24 m range. Main girder is made of prestressed concrete and it has a box cross section of a constant height. It is important to study the behaviour, not only in the transverse, but also in the longitudinal direction of the bridge axis, when analysing the bridge columns exposed to horizontal seismic actions. The columns were designed according to EN1992, parts 1 and 2. Seismic action analysis is conducted according to EN 1998: 2004 standard. Response spectrum type 1, for the ground type B, was applied and the analysis also includes 20% of traffic load. The analysis includes the values of columns displacement and ductility. To describe the behaviour of elements under the earthquake action in both - longitudinal and transverse direction, pushover curves were formed.

The authors of the paper, on the basis of the analysis of a large number of scientific papers, presented their original systematization of seismic analyses of structures, where a large number of them were developed during the last twenty years. Seismic analyses are generally classified into two (four) groups: Linear Static Analyses (LSA) and Nonlinear Static Analyses (NSA), and Linear Dynamic Analyses (LDA) and Nonlinear Dynamic Analyses (NDA). The analyses of nonlinear seismic structural response were classified separately from the Target Displacement Analyses (TDA) which defines the relationship of the seismic demand and seismic response. On the other hand, classification was also conducted depending on whether a nonlinear response of the system is obtained by the implementation of incremental-iterative procedures or by implementation of semi-iterative and/or semi-incremental procedures. NDA were classified according to the concept of mathematical formulation, i.e. whether they are based on only one dynamic analysis, several dynamic analyses or they are solved in combination with other methods. By implementing the conducted systematization of seismic analyses, one can efficiently consider which type of analysis is optimal for structural analysis and which type of analysis should be taken into account in the phase of preliminary and final analyses in the course of scientific research and professional projects. This paper also presents the aspects of damping modelling in structural analysis through the systematization of damping types and flowcharts, depending on the type of analysis applied: linear and nonlinear, static and dynamic. Damping has been systematized based on the way it was introduced into calculations, i.e. over material damping, link element damping and damping directly introduced into the analyses which are conducted in capacitive, time and frequency domains. In the process of creating numerical structural models, the type of damping and the way of its introduction into structural analysis can be very efficiently selected by applying the flow charts developed. By applying the developed flowcharts, alternative approaches to the introduction of damping into structural analysis can also be defined.

The paper deals with methodology developed and presented for analyzing the damage on structures exposed to accidental and seismic actions. The procedure is based on non-linear numerical analysis, taking into account the principles of Performance-Based Seismic Design (PBSD). The stiffness matrix of the effects of vertical action is used as the initial stiffness matrix in non-linear analysis which simulates the collapse of individual ground-floor columns, forming thereby a number of possible scenarios. By the end of the analysis that simulates the collapse of individual columns, the stiffness matrix is used as the initial stiffness matrix for Non-linear Static Pushover Analysis (NSPA) of bi-directional seismic action (X and Y directions). Target displacement analyses were conducted using the Capacity Spectrum Method (CSM). The structure's conditions/state was assessed based on the calculated global and inter-storey drifts and the damage coefficient developed. The damage level to the building was established using an integrated approach based on global and inter-storey drifts, so that, depending on the level of displacements for which the drifts are identified, a more reliable answer can be obtained. Applying the damage coefficient, a prompt, reliable and accurate indication can be obtained on the damage level to the entire structure in the capacitive domain, from elastic and non-linear to collapse state.

Almost to the end of the twentieth century durability was treated implicitly and its service life (SL) was not defined in technical regulations (codes) for the design of concrete structures (CS) which have been applied. Over time this approach has proved to be insufficient, especially in intensive growth environment pollution. In the current codes for the design of CS (e.g. EN, i.e. Eurocode - EC), durability is treated implicitly and most do not contain quantified guidance for the design of CS SL longer than 50 years. The SL is implicitly defined with no clear meaning, what is the end SL? It was considered that application of the provisions of these codes result in permanent CS service, and that they will achieve the required SL, which is often not the case. Experiences show that this approach fails to meet the requirements of durability, especially when the requested SL is significantly longer than 50 years (100 or more). Modern approach to the design of reliable CS is based on performance and behaviour during SL. Probabilistic approach (based on probability and reliability) design enables a more accurate forecast of the behaviour of CS during SL, but it is complex and the possibility of its wider practical application is in the developmental stage. Based on a review of literature and contemporary codes, the paper analyzed some models and approaches to the design of CS, according to durability. The emphasis is on the design of the performance, based on the indicators of durability of concrete, with current proposals for a revision of EN 1992 and EN 206, based on the experience gained and the latest research in this field.

The available experimental and numerical results of many studies of behavior of reinforced concrete connections for different stages of loading, up to fracture loading, are presented and analyzed in this paper. The problem of beam-column connection (or plate-wall connection) in prefabricated monolithic structures is emphasized. Fracture mechanisms of RC structures, the theoretical basis for their analysis, and the use of fracture mechanics in RC structures were also considered, as well as the mathematical models of prefabricated connections. In order to formulate an adequate mathematical model for calculating the connections, the dominant parameters influencing the behaviour of these connections were analyzed. A failure model for the prefabricated wall - monolithic RC plate connection was formulated. In building the model, the results of implemented experimental and numerical research of prefabricated connection in the MMS system from 2007 were used. Experiences with the implementation of the aforementioned construction system in structures in Tuzla, in the 1980's last century, were additionally used. The proposed mathematical models provide a sufficiently accurate failure assessment of prefabricated reinforced concrete connections.

Large panel residential buildings, dating from second half of 20 Century, are to be found in almost every urban settlement across Europe. Within the context of three case studies of urban blocks in Bulgaria (Mladost - Sofia), Macedonia (Karpos III - Skopje) and Serbia (Detelinara - Novi Sad), comparative analysis and evaluation of technical and structural characteristics according to reliability (seismic resistance and fire safety) and sustainability (energy efficiency, internal air quality, accessibility) criteria has been conducted. Additionally, previous experiences from individual renewal projects are reviewed. Previous experiences and comparative analysis results, could contribute to formulation of wider applicable solutions and development of new urban renewal strategies.

This paper analyzes application of modern reinforcement methods for reinforced concrete (RC) beams using fiber-reinforced polymer (FRP) materials. Basic characteristics of FRP materials and the method of mounting the FRP bars within concrete, that is, near the surface of the beams (NSM method) are presented. The properties of this method and its advantages in comparison to externally bonded reinforcement laminate method (EBR) have been analyzed. The results of measured deflections and width of the cracks of the beams reinforced by FRP bars, depending on the load are presented and discussed, in comparison to the results obtained from the non-reinforced beams. The experimental research was published at the Faculty of Civil Engineering and Architecture of Niš in 2009.

This paper is a sequel to [19] where the theoretical foundations were given for the analysis of durability of concrete structures. An overview of some approaches to modeling the durability of RC structures is given in the paper. Experiences resulting from experimental and numerical research of some influential parameters leading to corrosion of the reinforcement, cracks and delaminating of the surrounding concrete, which leads to the decrease of service life of the RC structure's elements, are described in details. Methodologies of structure evaluation presented in this paper are based on assessment of critical influential parameters and represent a methodology of reasonable maintenance of an engineering construction, i.e. reasonable service life of the structure. The methods are based on analysis of conditions and performance (Condition Rating Method and Performance Rating Method). The results of ratings of concrete structures in the industrial zone of the city of Tuzla are presented in the final part of the paper.

Thermal properties of the wall structure elements made from gel and straw ("Ethno-eco-passive houses") have been investigated. The gel was made from a mixture of clay, lime, and water. A 1-D mathematical model based on the continuum mechanics, for predicting the thermal conductivity, is proposed. The results obtained by applying the proposed mathematical model were compared with the measurement data of experimental tests, using the Isomet 2114 instrument. The program envisages the measurement of thermal conductivity of three specimens, 5-year-old, comprising three series within 365 days. In the theoretical analysis, the same parameters of thermal stability were treated as in the experiment. The average value of the material thermal conductivity is 0.0990 W/mK, so it can be concluded that, the composite material intended for the envelope of the proposed constructive system "Ethno-eco-passive house" is verified as thermally suitable. [ABSTRACT FROM AUTHOR]