Todorov, Koce
Preferred name
Todorov, Koce
Official Name
Todorov, Koce
Main Affiliation
Email
todorov@gf.ukim.edu.mk
19 results
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Item type:Publication, Base isolation as effective tool for plan irregularity reduction(European Association of Earthquake Engineering (EAEE), 2017-10); Lazarov, Ljupco - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Nonlinear Static vs. Incremental Dynamic Analysis of Infilled Frames with Open First Floor(Society for materials and structures testing of Serbia, 2018); Lazarov, LjupcoMasonry infill, as a part of building structures, is characterised with significant in plane strength and stiffness and it can greatly alter the response of structures exposed to seismic loads. Irregular distribution of infill in plane and along building height can lead to series of unfavourable effects (torsion effects, dangerous collapse mechanisms, soft or weak storey, variations in the vibration period, etc.). In order to investigate the influence of irregular distribution of masonry infill to the seismic performance of code designed reinforced concrete frames, an extensive nonlinear static and dynamic analysis was performed. Six reinforced concrete frames with different number of storeys, designed as bare frames were analysed. In the phase of assessment, all structures were upgraded with the masonry infill panels in all storeys except the first one. Masonry infill was defined with two different strength and stiffness characteristics. The obtained results show significant influence of masonry infill on the main structural characteristics: strength, stiffness and ductility, as well as on the seismic performance of analysed frames. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Seismic response of base isolated plan irregular structures(European Association of Earthquake Engineering (EAEE), 2018); Lazarov, LjupcoNine spatial five storey structures with different type and degree of plan irregularity are analysed in this paper. The seven structures have rectangular shape, while the other two have T shape in plan. The first structure with rectangular shape is regular. Three of the remaining six structures with a rectangular base, analysed as fix supported, do not comply the condition for maximum allowed eccentricity between the centre of mass and centre of stiffness and two of the other three do not comply the condition for torsional sensitivity according to which torsional radius should be greater than the radius of gyration of the floor masses. Base isolation significantly reduces eccentricity between centre of stiffness and centre of mass of the structures with stiffness eccentricity and increases the torsional radius on each floor of torsionally sensitive structures, which leads to compliance of previously mentioned criteria. Fast nonlinear time history analysis is applied to determine the dynamic response of base isolated structures. The results obtained for the isolated rectangular structures show great reduction of the torsional effects and the interstorey drifts, compared with the corresponding fixed base structures. Fixed base structures with a rectangular shape, has 4 to 5 times larger rotations compared with the isolated. In contrast, the maximal rotations of structures with T shape occurred at base isolated models. The maximal interstorey drifts at base isolated models are about 2.5 times smaller in comparison with fixed based. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Application of base isolation systems at plan irregular structures(Macedonian Association of Structural Engineers, 2017-10); Lazarov, LjupcoApplication of base isolation systems is one of the possible solutions to avoid the negative effects from irregularity of structures in plan. In order to investigate the advantages of the application of these systems, a detailed evaluation of the behaviour of six spatial five storey structures with different level of plan irregularity and different shapes in plan was performed. All structures are analysed as fixed base and base isolated. At irregular structures with rectangular shape in plan, base isolation significantly reduces eccentricity between the centre of stiffness and the centre of mass. Oppositely, in structures with “T” shape, eccentricity is larger at base isolated models. The maximal interstorey drifts of base isolated models are about 2,5 times smaller in comparison with the fixed base. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Stiffness Characteristics Modelling of RC Frame Structures According to Eurocode 8(Macedonian Association of Structural Engineers, 2010) - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Structural Application and Analysis of FRP Pultruded Elements(Macedonian Association of Structural Engineers, 2017-10); Chifliganec, CvetankaThe FRP elements obtained by the process of pultrusion are advanced, adaptable and in the hands of engineers open new horizons for application. They have their origin in the automotive and aviation industry, but in the last two decades their structural application has been intensified. This paper summarized their structural application, also gives an overview of current standards and codes for their design. Because the pultrusion elements are characterized by high strength, but small modulus of elasticity, most common form of collapse is due to local or global instability. Considering the orthotropic characteristics of the pultruded elements, shell elements are used in the software SAP2000 in order to analyze the forms of buckling that occur in elements exposed to compression and bending - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Seismic behavior of asymmetric structures with different degree of irregularity(European Association of Earthquake Engineering (EAEE), 2018); Lazarov, LjupcoIrregularity in plan can significantly affect the desired ductile response of structures exposed to earthquake loading. Most of the seismic design codes contain provisions for control of structural irregularities. According to EN 1998-1, a building can be characterized as regular in plan, if six different conditions were satisfied, at all story levels. Some of these conditions are qualitative, but some of them that are based on the determination of eccentricity between the center of mass and the center of stiffness or torsional radius, are quantitative. In order to investigate the influence that the degree of irregularity in plan has on the behavior of the buildings on seismic loading, several mathematical models of five story RC frame structures are analyzed. The degree of irregularity is regulated with the length of the seismic wall placed at the external frame of the structure. Nonlinear dynamic analysis is performed with purpose of numerical evaluation of the seismic behavior of the structures, whereupon input ground motions from three previous earthquakes are used, Imperial Valley – El Centro 1940, Victoria Mexico – Chihuahua 1980, Chi Chi Taiwan 06 – CHY028 1999. Input acceleration histories are scaled for three different levels of seismic hazard that correspond to PGA of 0.12g, 0.24g and 0.36g. In all analyses the seismic action was applied in one direction, perpendicular to the axis of irregularity. From the obtained results it can be noticed that the maximal displacements and the interstory drifts of the structure always occur at the most distant frame from the center of stiffness. The rotations that occur at the top story of the structure are not varying significantly with respect to the irregularity degree - Some of the metrics are blocked by yourconsent settings
Item type:Publication, New Polygonal Hysteretic Model for Simulation of Superelasticity Effect of Shape Memory Alloys(Society for materials and structures testing of Serbia, 2012); Petkovska Oncevska, SvetlanaThe term shape memory alloys (SMA) refers to the group of metallic materials that demonstrate the ability to return to the same predefined shape or size when exposed to an appropriate thermal procedure. The unique characteristics of SMA, i.e., the high damping capacity, the high level of stress and strains recovery, the re-centring capabilities and the high corrosion resistance make this material attractive for scientific research. This paper shows the general characteristics of the shape memory alloys and the main physical-mechanical properties of the most frequently used commercial alloys. Definition of a material model for numerical simulation of the superelastic response of shape memory alloys is very important for their mathematical modelling. For that purpose, a new original polygonal hysteretic model with variable tangent stiffness has been developed for description of the superelasticity effect in the case of cyclic axial loading The model has a number of advantages as are the simple algorithm for computation, the easy definition of the necessary material parameters by means of a uniaxial compressive or tension test, the different elastic characteristics in the austenite and martensite phase, the possibility of simulation of different loading conditions at cyclic loading and the easy implementation in some of the open software codes. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Strength, stiffness and ductility of masonry infilled frames under lateral loads(Association of Structural Engineers of Serbia, 2018); Lazarov, LjupcoMasonry infill is characterized with significant in-plane strength and stiffness and it can greatly alter the response of structures exposed to seismic loads. In order to investigate the influence of masonry infill on the behaviour of structures exposed to lateral loads, an extensive nonlinear static analysis was performed. Six reinforced concrete frames with different number of storey, designed as bare frames were analysed. In the phase of assessment, all structures were updated with the presence of masonry infill panels with two different strength and stiffness characteristics. The obtained results, expressed in terms of the comparison of capacity curves and stiffness degradation shows significant influence of masonry infill on the strength, stiffness and ductility of analased frames. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Incremental Dynamic Analysis of Infilled Frames with Open Ground Floor(European Association of Earthquake Engineering (EAEE), 2018); Lazarov, LjupcoReinforced concrete frames with masonry infill are often used structural systems throughout the world, especially in developing countries and countries around Mediterranean region. Irregular distribution of infill in plane and along building height can lead to series of unfavourable effects (torsion effects, dangerous collapse mechanisms, soft or weak storey, variations in the vibration period, etc.). In order to investigate the influence of irregular distribution of masonry infill to the seismic performance of code designed reinforced concrete frames, an extensive nonlinear dynamic analysis was performed. Six reinforced concrete frames with different number of storey, designed as bare frames were analysed. In the phase of assessment, all structures were upgraded with the masonry infill panels in all storeys except the first one. Masonry infill was defined with two different strength and stiffness characteristics. All frames were exposed to twenty-one different earthquake ground motions scaled to ten different amplitudes. In the case of low rise buildings, the presence of infill is usually unfavourable for all levels of PGA, leading to the formation of soft storey mechanism. In the case of midrise buildings, the presence of infill reduces the seismic demand up to the PGA of 0.3g. At high rise buildings distribution of damage depend on the mechanical characteristics of infill as well as the frequency content of input ground motion. The ratio between maximal interstorey drift and maximal top drift can be a good indicator of damage distribution thru the building height. In order to quantify this relationship, regardless of the number of storey, the parameter named as index for distribution of displacement at height (DDH) was defined.