Institute of Earthquake Engineering and Engineering Seismology

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SEISMIC SOIL-STRUCTURE INTERACTION EFFECTS ON A HIGH RISE RC BUILDING
(University of Zagreb Faculty of Civil Engineering, 2023-03-24)
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Bojadjiev, Jordan
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Nikolovski, Done
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Soil-structure interaction (SSI) is for sure one of the most neglected effects in seismic structural design practice. However, many researchers showed that it might notably affect seismic performance results. In fact, the stateof- the-art seismic codes are encouraging including SSI for structures with considerable p-Δ effects and mid to high-rise buildings. In the current research, seismic soil-structure interaction analysis is made for a selected midrise reinforced concrete building with several different SSI techniques (models). In order to quantify the effect of SSI on the overall response of the selected structure, the global seismic response within a frame of forcedisplacement relationship for different earthquake intensities, different SSI mathematical models and different soil categories is presented. Comparing the outcome of the performed analysis it was observed that the structural performance was affected significantly by the foundation system and contributes considerably to the overall structural performance of the selected structure in specific soil conditions. As the results indicate, more codebased recommendations are required for the improvement of the SSI structural seismic design, especially in soft soil cases, where the soil-structure interaction might significantly affect the seismic response of buildings.
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EFFECTS OF CORE STRUCTURE IN MULTIPHASE SIMULATION OF AN EARTH DAM
(University of Zagreb Faculty of Civil Engineering, 2023-03-24)
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Kitanovski, Toni
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Ivanovski, Dejan
One of the most popular themes in earthquake geotechnical engineering is the simulation considering the phase interaction among different phases inside the soil medium. The present article aims at providing numerical simulations of an earth fill dam composed of multiphase material models. Moreover, the assessment of liquefaction potential is investigated considering the presence of core structure inside the dam body which obviously has great implications for the results. The formulation of the coupled approach is presented as a mixture of three constituents – soil grains, water and air in the pores. Mixture theory is considered including the concept of volume fractions in defining of the coupled approach. An earth dam has a trapezoidal cross section with the presence of core structure inside the dam body. The flow of water is different and simulations are more time consuming for which results from literature are used in verification process. The simulation considers a nonlinear behavior with respect to the water retention curves and material model for the solid state. The hydrostatic distribution of water pressured at steady state conditions show obvious differences in saturation of the earth filled dam and are in accordance with the results from literature. The dam is assumed to be situated above a hard rock formation. The soil material of the dam body is simulated as hypoplastic material model which is nonlinear even for the small deformations. The usage of hypoplastic model and the accumulation of strain in each cycle of the stress – strain relation makes the model advantageous. Results are compared accordingly, and conclusions provide directions for further usage of the multiphase model in simulation of this type of structures
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Assessment of soil behavior in seismic excitations by exploring different approaches
(University of Zagreb Faculty of Civil Engineering, 2024-10-08)
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Stanko, Davor
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Salic-Makreska, Radmila
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In geotechnical earthquake engineering seismic site response analysis is a very complex task, which has gained an increasing importance for the last decades. This paper aims to numerically simulate the effect of an earthquake input in different types of soil layers in order to get the dynamic amplification factor. The methodology for correctly simulation of seismic waves propagation includes thorough theoretical background aided with different softwares (Shake, Strata,DeepSoil and Plaxis) which allow the simulation of soil as nonlinear material model or small strain linearly elastic material. The verification of the model is done by comparison of numerical results in relation to two different soil profiles from Varazdin, Croatia and from Skopje, Macedonia. The proposed approach should demonstrate and illustrate the special points in taking into account the modelling of different layers. The earthquake input is given as acceleration signal which in case of low densities of soil material are prone to initiate higher amplifications. Finally, the advantages and limitations of the proposed numerical model are discussed in detail.
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EFFECTS OF GROUND MOTION INTENSITY IN ASSESSMENT OF SOIL SLOPES IN EARTHFILL DAM
(University of Zagreb Faculty of Civil Engineering, 2025-03-19)
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Stanko, Davor
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Shalic-Makreska, Radmila
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The cumulative displacement of sloped soil masses in earth-fill dams subjected to seismic loading is fundamentally governed by both the magnitude and frequency characteristics of the seismic excitation. This correlation necessitates comprehensive numerical simulations incorporating diverse acceleration time histories to capture the full spectrum of potential seismic responses. This manuscript examines the response of an earth dam slope susceptible to seismically-induced instability under various earthquake scenarios with distinct magnitude-frequency characteristics. The accurate modeling of soil media becomes particularly critical in situations where dynamic pore pressure generation occurs within the soil matrix. The coupled numerical approach developed in this study conceptualizes the soil element as a three-phase medium composed of soil grains, pore water and pore air. The simulation considers a nonlinear behavior with respect to the water retention curves and material model for the solid state and analysis is performed by ANSYS and PLAXIS. The air pressure is assumed to stay atmospheric in the course of the calculation and matric suction is equal to a negative value of the hydrostatic stress in water pressure. The coupled model allows to take into account the deformations of the soil skeleton and simultaneously considers the pore water pressure change during the earthquake excitation. The seismic behavior of the slope gives interesting results considering both deformation and pore water pressure development. The primary objectives of this research are to investigate the seismic response of earth dam slopes under various earthquake scenarios and compare results between ANSYS and PLAXIS software implementations for multiphase soil modeling. The contributions include the development of a comprehensive coupled numerical approach that simultaneously considers soil deformation and pore pressure evolution during seismic loading along with the integration of hypoplastic material model with multiphase flow analysis.
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Improving the physical and mechanical properties of clayey soil by adding waste material  fly ash and stone flour
(Faculty of Civil Engineering and Architecture, 2025-09-11)
Marinković, Nemanja
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Zlatanović, Elefterija
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Bonić, Zoran
Stabilization of clayey soil with an inadequate physical and mechanical properties in its natural state represents one of the actual challenges in contemporary geotechnical engineering. Among numerous stabilization techniques, chemical stabilization stands out as an effective technique for stabilizing clayey soils. By applying this technique, various types of stabilizers may be used, whereby they react with soil particles and modify its structure, contributing to the permanent improvement of the physical and mechanical properties of the soil. In this study, waste materials obtained as a product of industrial processes, such as fly ash and rock flour, were considered as chemical stabilizers. A comparative analysis of the effects of adding fly ash and rock flour on improving the uniaxial compressive strength (UCS) and the shear strength parameters of clayey soil was performed, while simultaneously monitoring the durability of the achieved effects.
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Решенија за ограничување од облогата и хидродинамичка стабилност на јаловишна брана
(Сплит- ХрватскФакултет за Градежништво Архитектура и Геодезија; Матице Хрватске 15, HR-21000 Сплит, 2023-12-12)
Mircevska Violeta
The study investigates the impact of reservoir lining on the hydrodynamic stability of a tailings dam. A 3D coupled fluid-solid finite element model was used for detailed seepage analyses based on conventional flow-net and steady seepage conditions. Pore pressure, stationary seepage velocities, static liquefaction and the ratio between manifested and critical hydraulic gradients were predicted under three different lining conditions. The highest potential for internal erosion and heave was observed in the lined reservoir and starter dam scenario. Although there are environmental benefits, the incorporation of liners in dam design requires a comprehensive engineering assessment of the negative hydrodynamic effects.
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Influence of railway induced vibrations on structures and humans in urban areas
(Croatian Society of Civil Engineers - HSGI, 2022-10-10)
Naumovski Nikola, Hristovski Viktor, Krstevska Lidija
Rail traffic is a significant source of vibration that can affect the quality of life of people living near busy railways. The paper proposes an integrated methodology for analysis of the impact of vibrations from railway traffic on people and buildings and measures for reduction of their effect. The research has grasped in-situ measurements and numerical modelling of railway traffic-induced vibrations. The proposed integrated methodological approach is specifically implemented on the section of the active railway line Kumanovo-Deljadrovce, N. Macedonia. The knowledge gained in this research is intended to represent a good basis for defining national standards for this increasingly relevant issue.
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Quasi-static tests on RC building columns strengthened with CFRP
(Croatian Association of Civil Engineers, 2021-09)
Golubka Nechevska-Cvetanovska, Artur Roshi, Julijana Bojadjieva, Jordan Bojadjiev, Zoran Trajcevski
<jats:p>To explore the possibilities and benefits of using CFRP (Carbon Fibre Reinforced Polymers) in strengthening RC building columns, quasi-static tests (compression and bending) were carried out at the Institute of Earthquake Engineering and Engineering Seismology - IZIIS, Skopje by variation of concrete class, reinforcement percentage and by using various strengthening technologies. Some recommendations and outcomes regarding the approach, technology and conclusions drawn from practical application of these materials, are given. Based on the analysis of values obtained from nonlinear static and nonlinear time history analyses, it can be concluded that the ductility capacity for displacement of model strengthened with CFRP is greater by 60 %, while its strength capacity is greater by 7.7 % when compared to the values obtained for the model without CFRP. It can generally be concluded that CFRP systems are a very practical tool for strengthening and retrofitting concrete structures, as they can extensively improve flexural strengthening, shear strengthening, column confinement, and ductility.</jats:p>
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Analysis of exponent K based on “SHARE” project data and its implications on importance factors of EN 1998–1
(Springer Science and Business Media LLC, 2022-02-08)
Dragojević, Dejan
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Šalić Makreska, Radmila
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Milutinović, Zoran
This contribution deals with seismic activity represented by a hazard curve through a single parameter–exponent k as given in EN 1998–1 and its implications on importance factors. We used the SHARE project dataset to calculate exponent k for the wider European area, and a limited number of separate national studies for comparison of the results since comparison to the SHARE results on the same dataset resulted in values of exponent k smaller by 1–1.5. The results indicate that the recommended value of exponent k of 3 is rather an exception than an expected value in seismically active regions and that, with the exclusion of the Vrancea zone, for the majority of Europe, exponent k is well below that assumed in EN 1998–1, which consequently indicates that the importance factors for these locations should be higher than those recommended in EN 1998–1.
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Genealogy of development and codification of Yugoslavian earthquake resistant design
(Springer Science and Business Media LLC, 2022-08-30)
Milutinovic, Zoran
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Salic Makreska, Radmila
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Tomic, Daniel
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Trajcevski, Jovan
This contribution aims to clarify for exposure modelers and vulnerability and seismic risk assessors the basis on which seismic lateral loads have been established in all Yugoslavian seismic design codes since 1948. The particular focus is on JUS39/64 and JUS31/81 seismic design codes since they controlled the seismic safety of Macedonian (and Yugoslavian) exposure for 16 and 41 years, respectively. The analyses and discussions are centered on lateral force coefficients as a primary factor for representing the features of each design level. Presented is in all detail the developed K-Quotient method that efficiently compares inter-code lateral force levels. The method provides the closed solution for simplified lateral load calculation applicable to “stiff” buildings (T ≤ 0.5 s). The presented results are indicative of flexible buildings requiring further research on the subject.

Institute of Earthquake Engineering and Engineering Seismology

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