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In this paper, the seismic response of a three 5 story reinforced concrete (RC) frame system buildings is analysed through the fragility and vulnerability analyses. The constructions are designed in accordance with the structural Eurocodes. All three buildings have the same area, but different shape in the base. For the analysis of the response of structural system to the earthquake actions, the method of nonlinear static (NSA) analysis was applied and based on the obtained results, fragility probability density functions and vulnerability curves were constructed using statistical methods. Structural damage state threshold parameters are determined based on the methodologies described in RISK-UE project. Comparative analysis of the structural damage probability for the three analysed RC buildings is applied in both main directions and as the whole as well. Based on the analysis results, final remarks and conclusions were formulated.

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.

The robustness of a reinforced concrete (RC) five-storey building (frame system stiffened by walls) is analysed in the paper. A high ductility class structure is designed in accordance with structural Eurocodes. The response of the structure to eight different scenarios of the ground floor vertical element loss is analysed. Nonlinear Static Analysis (NSA) and Nonlinear Dynamic Analysis (NDA) methods are used for the robustness analysis. Fragility curves of the building are derived from statistical analysis of these results. The values obtained through NSA and NDA, damage limit states of the system, and fragility curves, are compared. The influence of the position of the removed element on robustness of the structure is also analysed.

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.

This paper formulates a mathematical model using the extrapolation of load-settlement curves with a rational function for analyzing the capacity of piles obtained from the static load test (SLT). In preliminary analyses, the extrapolation was based on the application of a number of mathematical functions that were gradually eliminated by iterative selection and filtering. The solution was obtained by extrapolation with a rational function. Using a rational function in the extrapolation of the load-settlement curve, a clearly identifiable part is obtained in which the asymptote is vertical, indicating the reached limit state of capacity in the soil and/or in the pile. The probabilistic analysis showed that no unique value for pile capacity was obtained, and that the spectrum of capacity values depends on the probability of occurrence of the corresponding event.

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.

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.

Over the last several decades, adhesive bonding has been validated as a good alternative to traditional joining methods in metallic construction. On the other hand, the main factor that limits the wider use of structural adhesives in civil engineering industry is scepticism about their long-term performance, especially when subjected to variable amplitude fatigue loading. Most of the research on predicting the fatigue life of adhesive joints subjected to this type of loading dealt with composite adherends. In this paper, straightforward method for prediction of strength degradation and fatigue failure under random spectrum loading is presented and validated for the case of adhesively bonded single lap joints made of aluminium adherends. It is based on the normalized strength reserve principle, proposed by the same authors in their previous research. The normalized strength reserve model is expanded to the case of variable amplitude fatigue, incorporating the cycle mix parameter in order to account for load interaction effects. Very good agreement was obtained between the fatigue life predictions of the presented method and experimental results from the literature.

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 presents the use of a numerical model based on layered finite elements in the analysis of stress and strain due to creep and shrinkage of concrete and relaxation of prestressing steel in statically indeterminate composite structures. The calculation algorithm allows significant changes in the structure through characteristic time intervals, in accordance with technological procedures used during realisation of works. The corresponding computer program adapted to daily practical engineering design is also developed.

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.

This paper presents the case study of the authors&rsquo, design of the earth-sheltered house in Village Dobraca near Kragujevac, Serbia, in the context of development and some thermal properties of the underground housing. The historical insight, in brief, provides a better understanding of the reasons for their modern use as energy efficient and sustainable structures. It shows that underground houses even today are more thermally efficient than above ground houses since, besides earth, there is no need for new additional thermal layers. The article also includes a review of the representative physical forms of the underground housing through different periods, with the result of measurement of their main properties. The study of the underground housing structures provides an insight of the relation between the location and typology of underground homes in a contest of climate zones. These structures have an almost constant temperature, which provides the primary &ldquo, comfort&rdquo, condition in which the man is determined to live in. The results on property-based monitoring data showed that the earth-sheltered house could provide the thermal comfort that is close to the ideal human needs temperature. Today, the new materials and especially the solar, geothermal, and wind accessories, enables the maximum sustainability of these specific building structures and provides them with an even better energy efficiency.

U radu je analiziran utjecaj momenta koji se prenosi spojem unutrašnjeg stupa i ploče, te utjecaj čvrstoće betona na nosivost ravne ploče na proboj. Sedam uzoraka u punoj veličini ispitano je eksperimentalno i numerički. Rezultati su prikazani u obliku krivulje opterećenje-rotacija ploče i uspoređeni s kriterijima loma prema teoriji kritične posmične pukotine (CSCT), kao i s približnim izrazima. Provedena je nelinearna analiza MKE uz kalibraciju modela s eksperimentalnim podacima radi boljega poklapanja numerički dobivenog odnosa opterećenje-rotacija s eksperimentalnim rezultatima., The effects of moment transfer at the flat-slab-inner-column connection, and the influence of concrete strength on the punching resistance of slabs, are analysed in the paper. Seven full scale specimens are investigated experimentally and numerically. The results are presented as load-rotation curves and compared with the critical shear crack theory (CSCT) failure criterion, and with other comparable expressions. A detailed nonlinear FEM analysis, involving calibration of model with experimental data, is conducted to ensure better correspondence of numerically obtained load-rotation relationship with experimental results.

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.

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 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.