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Choosing "an idealized model of the structure" in the classical theory of structures, connections between the members of the linear systems are usually adopted as ideally pinned or absolutely rigid. Ideally pinned connection does not allow relative displacement of interfaced sections foci, while sections can freely and independently rotate. The rigid connection does not allow both relative displacement and relative rotation. Numerous studies based on experimental results and numerical simulations, which were conducted over the last forty years, indicate that a large number of the node connections of members of linear systems can be classified neither as an ideally pinned nor as absolutely rigid. Systematization of recent results of scientific research, both theoretical and experimental work in this field in our country and worldwide, especially in the field of reinforced concrete linear systems, is performed in the first part of this doctoral thesis. The Chapter 1 presents an introductory discussion and an overview of the development of methods for analysis of linear girders, while in the Chapter 2 the results of the international project COST C1 ˝Semi- Rigid behavior˝ are analyzed in details, especially within the working groups for prestressed and reinforced concrete structures and seismic design. A special contribution to the study of this problem in our country is given by numerous theoretical and experimental works of the team of researchers from the Faculty of Civil Engineering in Niš under the leadership of Prof. Dr. Milic Milicevic. The theoretical approach to the design of structures with semi-rigid connections using the classical formulation of deformation method was analyzed in these works in details which an overview is given in the Chapter 3. Bearing in mind that the contemporary analysis of stress-strain state of complex engineering structures can not be imagined without a matrix formulation and implementation of electronic computers, the matrix formulation of structural analyzes of systems with semi-rigid connections is presented in the same chapter, which opens wide opportunities for relatively quick and simple analysis of these systems by use of modern methods of structural analysis. Variation formulation of the stiffness matrix and the equivalent load vector determination is shown in the Chapter 4, while the use of computers in the analysis of structures with semi-rigid connections is given in the Chapter 5. The results of the full size experimental analysis of a behavior of prefabricated reinforced concrete structures with semi-rigid connections carried out on the newly designed and constructed buildings Minoma and cold storage Lovopromet in Nis under static load are presented in the Chapter 6. In Chapter 7 is shown the experimental determination of the dynamic characteristics of structures by ambient vibration method which is performed on buildings constructed in structural systems Minoma and Amont in Nis. In the second part of the doctoral thesis experimental study is shown, which was realized in cooperation with the "Institute of Earthquake Engineering and Engineering Seismology" of the University St. Cyril and Methodius, Skopje, Republic of Macedonia, as a part of the static and dynamic stability attesting project of the standardized modulus of prefabricated RC halls program of structural system "AMONT", including analysis of obtained results, numerical modeling and calculation of reinforced concrete linear structures constructed in this system taking into account the real characteristics of connections. Almost all earthquakes that have occurred in the world in recent decades have caused severe damage or total demolition of precast reinforced concrete structures with semi-rigid connections (industrial iv halls and other various structures which differ in number of floors and ground floor typology). The most important is to provide that there are no human casualties during this damage, but the demolition of these buildings during the earthquake causes huge losses. In addition to the losses in terms of the economic value of the building itself, demolition most often has caused destruction of the very expensive industrial equipment. Modern technological lines in contemporary industry may be five to ten times more expensive than the value of the building itself. If the long-term economic consequences of the termination of the production process are taken into account, it is clear that the seismic safety of industrial halls is of vital importance in any seismically vulnerable region, which includes the territory of Serbia. In the second part of the doctoral thesis original results obtained on the basis of extensive theoretical and experimental research are presented with the aim to give adequate contribution in the field of real observation of present problems, in order to define the structural conditions and measures to improve the seismic safety of these specific structural systems. For this purpose primarily real phenomena and causes of damage and demolition of similar buildings during earthquake action are studied (Chapter 8). Based on the selected characteristic prototype of an industrial hall, which is widely present in Serbia, very extensive program of experimental research was carried out. These studies have provided original results and new insights into the real behavior of structural connections based on constructed full size physical models testing under the simulated cyclic load to the point of failure (Chapter 9). Improved methodological concept for nonlinear analysis of integral facilities with semi-rigid connections is formulated on the base of the experimental results by use of totally non-linear mathematical model (Chapter 10). A consistent theoretical procedure applicable for a detailed analysis of nonlinear seismic response of the systems with semi-rigid connections has been formulated and presented in the Chapter 11. The methodological concept of developed computer software used for detailed analysis of nonlinear seismic response of the selected prototypical building is presented in the shortest in the Chapter 12. The analytical part of the specific research includes the realization of extensive analysis of nonlinear seismic response of the selected characteristic prototypical industrial hall, with the aim to show the practical applicability of formulated analytical model and theoretical procedure for nonlinear analysis. The concept of formulated totally nonlinear mathematical model is shown in the Chapter 13, while in the Chapter 14 and the Chapter 15 the most significant results of the performed analysis of nonlinear seismic response of the building in transversal and longitudinal direction due to the effect of real registered earthquakes are presented. The fundamental facts that have been reached on the basis of completed complex analytical research are stated in the Chapter 16. Formulated and implemented detailed nonlinear analyzes enable improved design and wide practical application of standardized industrial halls and other facilities of this type in seismic zones of various intensity.Based on the results of completed integral theoretical, experimental and analytical studies, adequate conclusions and appropriate recommendations for further experimental and analytical research are summarized in the Chapter 17.

This dissertation contains analysis of reinforced concrete (RC) walls performance under seismic loading. Limit states, ductility and energy indicators of RC walls behavior are examined, along with their failure mechanisms. Sources of theoretical and experimental research of RC walls behavior under static load and load that simulates seismic action are thoroughly and critically examined. Proposal of a nonlinear mathematical model of RC walls behavior under cyclic load was provided, as well as a simplified model suitable for practical analysis Results of analysis are verified by the available experimental research. Nonlinear numerical models of RC walls are used in this study for simulation of seismic action impact on the multi-storey buildings in dual structural systems. Using adequate (here developed or modified) numerical model provides information about the parameters required for proper behavior of RC walls in concrete structures. Based on the proposed model, building structures of various layouts, heights and arrangement of RC walls were analyzed. The analysis was performed using nonlinear methods: static nonlinear (push-over) method and dynamic method which integrates motion equation (time-history method). Storey drift, maximum inter-storey drift and acceleration of ceilings are comparatively analyzed, as criteria for assessment of seismic performances, due to their direct influence on the damage of structural and nonstructural elements.