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The structures with semi-rigid connections comprise systems with the connections in joints which are not absolutely rigid, but allow, in general, some relative movements in directions of generalized displacements. Such type of connections is considered very little, or not at all, in designing of structures in today's engineering practice. If the influence of rigidity of semi-rigid connections is underestimated, and they are treated in the design as pinned, it has a negative impact on cost of a structure. But if it is overstated, the calculation results are not on the side of safety, what is reflected on bearing capacity, durability and stability, especially in the case of precast structures. Therefore Eurocodes take due account to the structures with semi-rigid connections. Matrix formulation of the analysis of systems with semi-rigid connections opens wide possibilities for relatively easy calculation by use of computers that is shown by example of seismic design. The interpolation functions, stiffness matrix, equivalent load vectors, and the consistent mass matrix are presented in this paper, particularly with an emphasis on systems with semi-rigid connection.

Criteria that are adopted in earthquake resistant design of pipelines and gas lines have to take into account seismic movements and seismic generated forces that are of significantly high probability level of appearance along the length of pipeline. A choice of criteria has to include an acceptable level of seismic hazard, while design criteria should be calculated. Seismic hazard is defined as a part of natural hazard and means probability of appearance of earthquake of corresponding characteristics in certain time and place. For design needs and calculation of influences caused by seismic forces the most important is seismic hazard of maximal horizontal acceleration due to ground vibration during earthquake. The methodology of seismic hazard calculation as base for micro seismic zoning is presented in the paper. It is shown calculation of seismic hazard of maximal horizontal acceleration due to ground vibration that is applied for 985 points at the territory of Republic of Serbia, based on which maps for return periods of 50 and 200 years are drawn.

Most often, in the case of typefied prefabricated systems, foundations are designed and constructed as prefabricated elements as well. When the structure is exposed to high intensity loading and founded on a weak soil, beam foundations are often used instead of pad foundations. Beam foundations, stiffening girders, as well as beams which support the façade elements or partition walls, are treated as beams on elastic foundations, while joint of these girders to pad foundations or vertical support elements of a precast structure can be treated as semi-rigid. Modeling of systems with semi-rigid joints on elastic foundations, for different levels of rigidity of connections, is illustrated by an example of a frame under static loading. On the basis of the results of the calculation carried out in this paper, it is evident that taking into account the elastic foundations of the member and the corresponding degree of fixation of the member on this foundations significantly affects the magnitude of the forces in the cross-sections of the member, and on the redistribution of influences in the entire structure. Yet, the foundations-and-soil interaction exerted the highest influence on the magnitude of the stress in the foundation structure itself.

The assumptions and basic equations of the first-order shear deformation plate theory of Mindlin, as one which provides more accurate solutions compared to the classical theory, are briefly presented in this paper. Application of one analytical solution derived according to this theory is presented by use of example of stress-state and deformations calculation of the reinforced concrete footing, which has been the object of recent author's experimental research. Numerical results obtained by applied procedure, which refer to the elastic domain of material behavior, are compared with experimentally obtained data of deflections of footing plate midpoint. .

The paper deals with a brief presentation of a part of the performed experimental tests of the prefabricated reinforced concrete structural system 'AMONT' for construction of various types of modern industrial halls. The test results are analyzed for two industrial halls both constructed according to this structural system but in the different phases of construction, tested in the full scale by application of AMBIENT vibration method. From the obtained Fourier spectra for measured ambient vibrations in two orthogonal direction for the structure without walls and the other with façade and filling walls, a significant discrepancy in their natural frequencies has been observed, and some conclusions about the influence of panel walls on dynamic characteristic the frame structure have been drawn out. The paper used some data of the research after the earthquake in Montenegro which took place on 15th of April 1979.

Material models describe the way they behave when loaded. The paper presents the development of the model beginning with the simplest linear-elastic and rigid-plastic ones. The basic data in the plasticity theory have been defined, such as criterion and yield (failure) surface, hardening law, plastic yield law and normality condition. Yield criteria of Tresca, Von Mises, Mohr-Coulomb and Drucker-Prager were given separately.

The paper presents a brief description of experiment within the research project 'Theoretical and experimental analysis of interaction of shallow reinforced concrete foundations and soil for the purpose of improvement of national regulations and implementaation of Eurocode system' where in situ tests of a series of reinforced concrete foundation footing were performed, by loading until failure. As a rule, methods for calculation of shallow foundations settlement on granular soils overestimate the expected settlement, and underestimate soil bearing capacity, which results in a conservative foundation design. In order to test accuracy and reliability of the different settlements prediction methods, a comparative analysis of settlements calculated using these methods and those measured during experiment, was performed.

Application of systems for passive vibration control is an efficient way for seismic protection of structures. Systems for passive vibration control consist of seismic isolation devices and energy dissipation devices. Base isolation of structures is a concept where devices for passive vibration control are placed in foundations of buildings. Various energy dissipation devices have been developed and tested so far, while metallic dampers represent a significant class. Those devices dissipate energy through the yield of metal material which they are made of. The metallic dampers have often been used because of their main advantages reflected in stable hysteretic behavior and well-known models for analytical prediction of the dissipated energy and structural response. Most of the metallic dampers have been developed for application in the beam-column joints or in the bracing system. The innovative energy dissipation device named multi-gap multi-level multi-directional seismic energy absorber, intended for the application in the horizontal seismic dilatation in the system of base isolation, has been developed recently by the group of the authors among whom is one of the authors of this paper. The main parts of the absorber are vertical components with linearly changeable circular cross-section. Due to the lateral displacements of the isolated structure the vertical components bend and energy dissipation is provided by yielding of the steel material they are made of. According to the previous experimental and numerical study of the absorber's vertical components, three-dimensional finite element model of the absorber has been developed and presented in this paper. The aim of the numerical analysis is to determine mechanical properties of the absorber based on the lateral force-displacement diagram. Furthermore, a simplified numerical model using one-dimensional beam finite elements has been proposed. The performance of the absorber has been determined using the available semianalytical solution for elastoplastic deflection of non-prismatic cantilever beams previously developed by the first author as well. The obtained results have been compared and it has been concluded that all three modelling approaches provide reliable mechanical properties of the absorber necessary for dynamic analysis of structures in engineering practice. [ABSTRACT FROM AUTHOR]

Strengthening of concrete structures is applied as a solution for various deterioration problems in civil engineering practice. This also refers to the structures made of self-compacting concrete (SCC), which is increasingly in use, but there is a lack of research in this field. This paper presents an experimental analysis of flexural behavior of reinforced concrete (RC) continuous beams made of SCC, strengthened with fiber reinforced polymer (FRP) materials (glass (GFRP) and carbon (CFRP) bars, CFRP laminates), by the use of near surface mounted (NSM) and externally bonded (EB) methods. Six two-span continuous beams of a total length of 3200 mm, with the span between supports of 1500 mm and 120/200 mm cross section, were subjected to short-term load and tested. The displacements of beams and the strains in concrete, steel reinforcement, FRP bars and tapes were recorded until failure under a monotonically increasing load. The ultimate load capacities of the strengthened beams were enhanced by 22% to 82% compared to the unstrengthened control beam. The ductility of beams strengthened with GFRP bars was satisfactory, while the ductility of beams strengthened with CFRP bars and tapes was very small, so the failure modes of these beams were brittle. [ABSTRACT FROM AUTHOR]

Self-compacting concrete (SCC) is a type of concrete that is placed in the formwork under its own weight. Although there are many studies showing the behavior of SCC beams, most relate to the behavior of simple supported beams. Unlike those, this is a study of continuous beams made of SCC aimed to analyze their flexural performance as well as to confirm the possibility of using nonlinear finite element analysis (FEA) in the design of such structural elements. An experimental study of three two-span continuous beams of a total length of 3400 mm, with the span between supports of 1600 mm, with 150/200 mm cross section made of SCC exposed to short-term loading, was carried out. The parameter that varied is the percentage of tensile reinforcement, with values of 0.65, 0.86 and 0.94 being selected. As all analyzed beams have shown a satisfactory load-bearing capacity and stiffness, the research confirmed the possibility of using SCC in continuous beams in civil engineering practice. Using Abaqus/Standard software, a nonlinear numerical model is proposed, which is validated and verified against experimental research, as there is only a 5% difference in the numerically calculated ultimate load compared to the experimentally measured values. [ABSTRACT FROM AUTHOR]