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The results of the experimental research program realized on a bridge model constructed by using the seismically isolated system upgraded with space-bar devices (USI-SB) are presented in the paper. The installed adaptable system for seismic protection of bridges utilizes double spherical rolling seismic bearings (DSRSB) as seismic isolators, while the qualitative improvement of seismic performances is achieved through the use of novel adjustable multi-directional space-bar energy dissipation (SB-ED) devices. The experimental program consisted of quasi-static testing of isolation and energy dissipation devices under the cyclic loading and extensive shaking-table testing of a large-scale bridge model with installed USI-SB system. For both types of devices, a very stable all-directional response during cycling tests, as well as the favorable hysteretic behavior of the energy dissipation devices along the entire range of applied large displacements were registered. In the dynamic testing, the system showed high seismic response modification performances needed for the efficient protection, exhibiting its large potential in the qualitative improvement of seismic performances of isolated bridges.

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.

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.

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.

The objective of this study is to investigate seismic response of bridges with unconventional configuration such as skewed and curved bridges. The influence of skewness and horizontal curvature on seismic performances of bridges, with a special focus on their influence on the probabilistic seismic demand model (PSDM), is analysed. Since the studies of seismic performances of bridges are nowadays formulated in probabilistic frameworks it is important that the established (PSDMs) meet specific criteria so they can be considered a reliable tool in seismic assessment of bridge structures. Twelve types of bridges are considered in this study by varying two bent types, three values of skewness and two values of curvature. Nonlinear dynamic analyses are conducted for all the considered samples. Longitudinal, transversal and resultant column drift ratios are considered as the bridge response. Five earthquake intensity measures are investigated and each of them are calculated from both horizontal components. In addition, the resultant measures are obtained by applying the SRSS rule on the components. The formed PSDMs are analysed in order to examine their efficiency, proficiency and sufficiency. Adverse effects of skewness and curvature on seismic performances of bridges are noticed in the conducted analyses by comparing mean values of column displacement ductility, established prediction models and fragility demand curves. It was noticed that these effects are more prominent for bridges with single pier bents with one weak direction in comparison with double pier bents. Finally, it is found that more accurate models (efficient and proficient) are obtained when structure dependant measures are used in PSDMs. Modified models including resultant measures and resultant response are proposed for fragility analysis of curved and skewed bridges.

The revitalization of existing masonry buildings, built decades ago, is a very topical and complex structural engineering issue, especially when the building was built in the area of significant seismic activity. A large number of masonry buildings in the city of Niš, as well as in other places in Serbia, were built in the period before the adoption of technical regulations on the design and construction of seismically resistant structures and they are at insufficient safety level in the event of an earthquake. Therefore, it is necessary that structural strengthening meets the seismic resistance requirements laid down in Eurocode 8 or other relevant codes. In order to choose the method of structural strengthening, detailed seismic analyses must be carried out in several variants along with the application of relevant technical regulations. The effects of five analyzed structural strengthening methods were checked against the provisions of Eurocode 8, Part 1 and Part 3, which relate to the recommendations for the geometric characteristics of shear walls, and they were applied on two types of existing masonry buildings in Niš. On the basis of the performed analyses, conclusions were drawn regarding the methodological approach of the assessment of the condition of the structure, its seismic resistance and decision-making on remediation and/or strengthening measures.

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.

This paper involves the analytical and numerical calculations of the the largest pre-stressed concrete free-standing structure in the world – the Dome of the “Hall 1 of the Belgrade Fair”, designed by a well-known Serbian scientist and engineer Branko Žeželj, one of the founders of the Institute for testing of materials IMS in Belgrade, conveniently positioned just across the street, best known for coming up with a concrete pre-stressing system, which is still widely used today. As a part of this research, this large and unique structure will be analyzed from point of view of structural integrity, including numerical simulation of crack growth in one of its support columns. Presented analyses also include the calculation of forces and moments in the structure as a whole, while also taking into account foundation displacements in the columns.

Residual strength models are widely used for the fatigue analysis of composites subjected to both constant and variable amplitude fatigue. However, they often require large experimental efforts to determine the model parameters. The aim of this research is to develop a simplified mathematical model which uses a single set of parameter values to predict the strength degradation of the elements subjected to different load levels, and thus, to reduce the required experimental effort for the determination of model parameters for each load level separately. The new two-parameter model is developed here on the basis of normalization of the difference between the residual strength and maximal applied load in the constant amplitude cyclic loading, herein referred to as the strength reserve, with respect to initial conditions. The model is validated using different experimental data sets from the literature. High correlation with the experimental data is observed. Moreover, the curves obtained by using the single set values of parameters matched the curves of some of the most accurate residual strength models from the literature.

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.

This paper elaborates the formulation and application of an integral methodology for overall energy performance improvement of office buildings and demonstrates its application. The developed multi-objective methodology is demonstrated on a reference office building located in a temperate climate zone with high annual temperature variations. The idea is to formulate a research based proposition in building science with a formulation of a general/integral methodology which could be applied widely in energy performance refurbishment of existing office buildings and help architects and engineers in the early-design stages of new projects. The goal was to formulate an optimized building envelope model using multi-criterion optimization methodology in order to determine efficient window to wall ratio (WWR) and window geometry (WG) in the function of indoor illumination quality, followed by the assessment of glazing parameters influence on the annual energy demand. The integral methodology for overall energy performance improvement of office buildings utilizes multi-criterion optimization method and highly detailed Building Information Modeling (BIM) programs and dynamic energy simulation engines. The developed coupled-integral methodology links together both building envelope construction optimization and user comfort. The methodology is both flexible and adaptable for application in various climatic conditions and for different construction types.

On the territory of Montenegro, road straight and curved bridges with middle range spans are often frame structures with multi column bent type and a capping beam. This paper presents the response of tree RC bridges: two curved bridges (with radius R=250 m i R=150 m) and one straight bridge. Bridges under consideration are frame structures with multi column bent (two circular columns) and capping beam integrated into the deck. Skewness of the bridge bent is also considered in this paper. Tree angles of skew are analyzed: 0˚, 20˚ and 30˚. Significant mode shapes are obtained through modal analysis. Comparative analysis of modal responses is carried out and conclusions about the influence of skewness and horizontal curve on modal shapes and periods of vibrations are made. Static-nonlinear analysis was performed for all nine bridge prototypes. The obtained results were compared and conclusions about influence of considered geometric parameters were made.

A semi-analytical procedure for the determination of the critical force of a pin-ended column loaded by axial force and bending moment is proposed. It is based on the principle of minimum potential energy of internal and external forces. The equations for strain energy have been derived for the first- and the second-order displacements per section, including compressed and tensile concrete and reinforcement. The energy of the external forces with axial and flexural displacement effects has been derived on the assumed sinusoidal deflection curve. The trapezoid rule is applied to integrate the segment internal energy. The proposed method uses a non-linear stress–strain curve for concrete; bilinear elastic–plastic relationship for reinforcement; equilibrium conditions at a sectional level to generate the strain energies along the member. The effects of shear deformations are neglected. The effect of lateral confining by the stirrups to strength is also analysed. The results obtained with the proposed model have been verified and compared with experimental results from the literature.

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.

century, at the time of intense urban development and migration into urban areas in Europe. These buildings need retrofitting to comply with contemporary demands of building performances. The directive [1], among other requirements for the planned maintenance of essential properties during the service life, sets for thermal comfort and energy savings. During RB service life, it is necessary to monitor the structure's performance through regular inspection of deterioration and other defects, investigate and detect the emerging problems and control the appropriate maintenance works [2]. The service life depends on the physical deterioration of materials and limitation of applied solutions, as well. The energy efficiency, especially thermal protection of buildings is a problem whose solution may also include the issues of technological, economic, social, legal, and moral obsolescence [3] of the existing residential buildings that were built in an industrial manner. Therefore, it has to be primary assessed so the energy rehabilitation measures could be set as compatible to the other building renewal activities.

This paper presents the comparative analyses of experimental and numerical research results of RC connections between the precast slab and monolithic wall (Type 1), and both monolithic slab and wall elements (Type 2). Type 1 was applied in prefabricated building system developed in Tuzla, Bosnia and Herzegovina, as the most sensitive part of the structure. In order to provide a favourable response of the bearing structure connections under seismic load (Type 1) it is dislocated in the span. In order to compare the behaviour of listed structure connection types, three specimens made of precast slabs and monolithic wall as well as three specimens made of monolithic slabs and walls were tested under quasi-static load. Thus, the mathematical models are proposed in order to analyse both types of connection, based on the exact method of displacement and FEM. Furthermore, the stiffness matrix is modified by introducing the stiffness parameter (semi-rigid) connection. The approximate Strut and Tie model is proposed according to the stress field analysis obtained by FEM.

Within the context of two case studies of complex industrial structures located in an aggressive environment, the issue of durability of reinforced concrete (RC) has been considered. Recommendations and guidelines of the International Association as well as some code provisions with regard to durability of RC structures were analyzed. Structures of the cooling tower (both of the shell and sprinkler) and the structure of Salt factory are presented briefly. The results of visual inspection of combined non-destructive and destructive investigation methodology of the concrete’s physical and mechanical properties as well as chemical measurements are presented. Parameters of the structures’ condition rating according to CEB (BI 243:1998) and a parameter recently introduced in fib (TG 5.3:2008) performance index are analyzed. These evaluations are valuable for condition assessment and taking decision about the level of repair of the heavily corroded structure. Conclusions are drawn up due to the analysis of the obtained results and on comparative analyses, and they relate directly to the state of the art system in this field. Clear recommendations in regard to RC structure durability analysis are considered by means of verification the limit state of depassivation and the reinforcement corrosion induced by chloride ingress.

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.

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 Nis in 2009.

Concrete structures (CS) are designed so that they can satisfy requirements regarding safety, serviceability, durability and aesthetics throughout their design service life. Present design procedures regarding CS required by national or international codes and standards such as Model Code Euro International Committee of Concrete (1993) now Federation Internationale du Beton (FIB), Eurocodes, ACI, RILEM, etc. are predominantly based on strength principles and limit state formulation. The durability aspect is a natural extension of the classical resistance verification where deterioration effects are normally neglected. The reliability is assessed through the given performance that must be delivered within the design service life, the so-called performance-based design. This approach can be adopted for a performance based on service life design. In the recent years design is related to durability through the analysis of carbonation, resistance to chloride ingress, improved freezing and thawing resistance, etc. The review of literature and some recommendations are presented referring to the design of structures aiming to attain greater durability of CS. The accent is put on the theory of reliability, failure probability and service life probability. The basics of this analysis are given through the principles of performances and service life, and deterministic and scholastic methods using the lifetime safety factor.

Experimental research of precast plate-monolithic wall connection within specific system developed in Tuzla, Bosnia and Herzegovina, in 80’s named “MMS” building system, is presented. System MMS is precast — monolithic building system specially adapted for high building constructions with characteristics of repetition of specific number of similar floors. The connections of monolithic wall and precast plate are executed with a dislocation potential joints opening which provided the structure displacement under seismic load. In this way joints become available for inspection and possible reparation/rehabilitation. The aim of presented researches is to determine the degree of connection loosening (yielding). The results of experimental tests will be used for numerical modeling of connections, which will be presented in forthcoming paper.

The construction of a multi-storey parking garage in Kikinda, Serbia started 20 years ago. The bearing structure was made of precast concrete columns, beams and ribbed floor slabs. After building of the bearing precast structure, the works were stopped and the unprotected structure was exposed to atmospheric influences (snow, rain, low temperatures). Many of the structure's elements were subsequently damaged due to insufficient concrete cover, badly performed reinforcement and incorrect manipulation of elements during erection. The initial defects and damage worsened to the extent that they not only severely affected the durability of the structure, but also jeopardised the stability and bearing capacity of some structural elements. Fissures and cracks, concrete spalling and reinforcement corrosion were registered on most of the structural elements. This paper presents the damage recorded, and the characteristic instances are illustrated by photographs. The results of subsequent testing of quality of built-in materials (concrete and reinforcement) are presented separately. To establish the actual condition of the bearing structure of the garage, an examination was done under load testing. The analysis of the results of in-situ and laboratory testing and the data gathered through detailed visual examination provided the basis for real assessment of the structure. Some specific repair solutions for durability improvement and insuring of load bearing capacity and stability of the existing structure are also presented.

The paper provides an overview of ambient vibration tests and numerical analysis performed in the framework of Project NATO SfP 983828. The aim of the research is the definition of the dynamic characteristics of bridges on the examples. The paper considers three case studies: two older existing bridges and one newly constructed bridge. A comparative analysis of natural frequencies and mode shapes, obtained by ambient vibration measurements (AVM) and mathematical models (AMs), was carried with the aim to demonstrate the usefulness of ambient vibration tests for identification of the modal parameters of the tested bridge structure. Agreement between AVM and AMs results is very good. The mode shapes are very similar. Some differences between computed and measured frequencies were obtained, which can be attributed to the real nature of the boundary conditions, the uncertainty in the material properties of structure elements, and the mathematical models assumptions.

U radu je dan pregled istraživanja provedenih u okviru NATO projekta SfP 983828. Predmet istraživanja je identifikacija parametara koji utječu na dinamički odziv postojećih armiranobetonskih grednih mostova, utemeljena na mjerenjima ambijentalnih vibracija i numeričkim simulacijama uporabom modela na bazi konačnih elemenata (MKE). U tu je svrhu instrumentaliziran most preko rijeke Bosne u blizini Sarajeva. Urađena su ispitivanja ambijentalnih vibracija i geofizička istraživanja. Rezultati su analizirani i urađen je poboljšani trodimenzijski numerički model koji uzima u obzir interakciju tla i konstrukcije, kao i interakciju gornjeg i donjeg stroja mosta. Razvijeni su modeli s projektnim parametrima i parametrima dobivenim mjerenjem. Urađena je komparativna ocjena razvijenih modela i verificiran model koji je imao vrijednosti dinamičkih karakteristika konstrukcije podudarne mjerenim vrijednostima. Rezultati analize pokazuju da je odgovarajuće određivanje krutosti stupova, kolovozne ploče i ležajeva ključni parametar za pouzdanu identifikaciju sustava., An overview of research performed in the framework of the NATO Project SfP 983828 is given in the paper. The scope of the research was to identify the parameters affecting the dynamic response of an existing R/C girder bridge, based on ambient vibration measurements and numerical simulations using finite element models (FEM). For this purpose, the bridge across the river Bosnia near Sarajevo and the soil surrounding the bridge were instrumented. Ambient vibration tests and geophysical investigations were performed. The results are studied and a refined three-dimensional (3D) FEM is developed that takes into consideration the soil-structure interaction and superstructure-substructure interaction. The FEM’s with designed parameters and parameters obtained by measurements were developed. The developed FEM models are comparatively assessed and FEM model with congruence between the measured and computationally predicted dynamic characteristics of the structure was defined. The results of the analysis show that the adequate determination of the pier, deck and bearings stiffness is the key parameter for reliable system identification.

The fire which spread over the top six floors of the 54 m tall building of the Open University in Novi Sad, caused severe damage to the load-bearing reinforced (RC) concrete structure and the steel facade structure. This paper presents the recorded data on the damage and the assessment of the structure after the fire. All the damage is described and the most characteristic ones are illustrated with photographs. The damages caused by the fire have been classified according to the criteria of the manner and degree to which they are manifested. The authors separate and describe the defects, which occurred as a result of errors made during the construction of the building. The results of the subsequent testing of the quality of the built-in materials are also presented in the paper. It has been concluded that the damage of the elements of the load-bearing RC structure from the 8 th to the 12 th floor has been so severe that the stability and bearing capacity of this part of the structure has been jeopardized, but with appropriate repair measures it can be restored to its previous condition.

The characteristic damage and repair of four silo cells for white soya flakes are described in the paper. Cylindrical steel cells, with 6 m diameters and 15 m high, are placed upon RC structure composed of a ring beam supported by eight columns 7.5 m high. The silo is so designed that the loading is transmitted and distributed uniformly on the ring beam. Filling and emptying of the silo is automatic by use of vibrating exemptor. After 10 years of service, the following damage was registrated on the structure: buckling of the vertical steel stiffening ribs of the steel envelope in the supporting zone, strains and cracks on the horizontal leg of the steel angle bar. On that basis the causes of damage were identified, among which the most important are: 1) imperfection at contact between the supporting part of the cell and the RC ring, so that instead of the contact along the total surface, concentrated supporting occurred along the beam; 2) eccentricity of the cell in horizontal plane in relation to the RC ring which caused uneven loading of the ring; 3) additional dynamic loading caused by the emptying equipment. By the repair design two variants were considered. In the first variant, the strengthening of the supporting part of the cell is proposed by welding additional steel plates to form a ring of box section with corresponding stiffening ribs. Besides, the way the cell leans on the steel structure is changed, so that centrally above the columns neoprene bearings are designed. For their installation the elevation of the cell is assumed by means of hydraulic jacks. Thus the static system is changed, i.e. the way of loading transmission by unloading the RC ring. According to the second variant, the repair should include strengthening of the RC ring by additional reinforcement and by concreting a new layer after injecting the cracks. Cost analysis of the variant solutions showed that the first one was more acceptable, and consequently it was realized. Inspection of damage, testing of structure, production of design and repair works were done in the period June–October 1992.

The paper summarizes an example of assessment of a cable-stayed pedestrian and motorway overpass in Tuzla city urban environment based on static and dynamic tests. The outlined research included testing of bridges induced by vehicles, ambient vibration testing, modal identification, finite element modelling and assessment of structural behaviour. The field investigations involved measurement of deformations (displacement and dilatation), vibrations induced by vehicles and ambient vibrations. Modes were identified by using Enhanced Frequency Domain Decomposition techniques (frequency domain). Details on the experimental procedures, instrumentation and data analysis techniques are presented and discussed. In the numerical study, deformations forms and vibration modes were determined using a 3D finite element model of the bridge and the information obtained from the field tests. Some conclusions and recommendations for similar bridges were given at the end of the paper.

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.

The paper presents a multidisciplinary approach to the assessment of seismic performances based on the Performance-Based Earthquake Engineering (PBEE), taking into account the multi-criteria optimization theory in analyzing the priority methods for bridge rehabilitation/strengthening. One bridge model was subjected to nonlinear static pushover analyses (NSPA), target displacement analyses using the spectrum capacity method (CSM), vulnerability analyses, and reliability analyses, while for a damaged bridge, in addition to be considered using the above methods, was also analyzed using the VIKOR method of multi-criteria optimization. Seismic performances were determined based on monitoring the system's plastification and analyzing the relevant parameters for the level of target displacement, such as target displacement, total shear force, spectral displacement, spectral acceleration, vibration period, damping and ductility. The phases of damage were considered using the probabilistic analysis of vulnerability and reliability: slight, moderate, extensive and complete, as a function of system ductility.