Julijana Bojadjieva

Ss. Cyril and Methodius University in Skopje · Department of Geotechnics - IZIIS

Landslides as secondary seismic effects are causing some patterns of soil failure that are often considered among the most destructive ones. In fact, the impact from triggered landslides has sometimes exceeded damage directly related to strong shaking and fault rupture. The objective of this research study is landslide hazard and risk assessment co...

Proceedings of the XVII ECSMGE-2019", Geotechnical Engineering foundation of the future

Within the presented research, model tests were performed in 1-g conditions to investigate the liquefaction potential of Skopje sand as a representative soil from the Vardar River’s terraces in N. Macedonia. A series of shaking table tests were performed on a fully saturated, homogeneous model of Skopje sand in the newly designed and constructed la...

Extensive monotonic and cyclic tests were accomplished on the triaxial and simple shear apparatus in the Laboratory for Soil Dynamics and Foundation Engineering at IZIIS.

The city of Skopje has suffered an earthquake in 1963 with a magnitude 6.3. Based on the damages to the building environment, the earthquake intensity was classified as zone IX, due to the catastrophic failure observed in the building stock. Yet, almost not a single damage associated to the geotechnical conditions of the ground has been reported du...

The ideal container is the one that gives a seismic response of the soil model identical to that obtained in the case of the prototype, i.e., the semi-infinite soil layer 1D response under vertically propagating shear waves. The boundary conditions created by the model container walls have to be considered carefully, otherwise the field conditions...

Since, in this book, a comprehensive experimental investigation was performed on a new type of sand—the Skopje sand, the necessity for numerical analysis of the experiments arose due to the following purposes.

In seismic regions, understanding soil–structure interaction (SSI) is crucial. This study examines the SSI effects on a six-storey RC-frame building using American guidelines for soil types B and C as per Eurocode 8. Structural responses of a constant structural system under various soil types and embedment conditions are compared, revealing signif...

Europe is characterised by a high level of seismic risk, both in terms of intensity and frequency, as evidenced by the significant damage caused to the region's building heritage. Italy is one of the most seismically active areas in the Mediterranean Basin, having experienced several destructive events in recent decades. Therefore, it is essential...

High energy demand forced many countries to reopen or expand production of electricity from coal power plants. Apart from being one of the most polluting technological processes emitting millions of metric tons of carbon dioxide in the atmosphere. This process also produces an enormous quantity of coal fly ash which has been successfully used as a...

CRISIS project aims at improving the disaster and emergency management through building a harmonized and efficient system for risk assessment of basic services and transport infrastructure in the targeted cross-border region. The main project activities include: (1) Cross-border multi hazard assessment; (2) Needs assessment; (3) Cross- border multi...

During the last 20-25 years Skopje, and more specifically Vodno mountain, has been exposed to intense urbanization, population growth, followed by intense anthropogenic processes such as application of structural loads, vegetation cuts and excavations, which have significantly changed the initial conditions of the terrain. These factors, along with...

Field investigations, testing and monitoring of structures and soil conditions is an imperative for precise decision making. When the time and the access to the location are additional constrain, having a reliable and comprehensive mobile laboratory equipped with state-of-the-art equipment is a huge advantage over conventional field investigations...

It is a usual practice that traditional methods with traditional materials (most frequently jacketing of elements) are used for repair and strengthening of structures. However, lately, particularly in the last two decades, there have occurred new construction materials intended for strengthening and design referred to as composites strengthened by...

The need for repair and strengthening of RC buildings and their structural elements occurs when their elements do not possess sufficient strength, stiffness and/or ductility out of different reasons or due to slighter or more severe damages most frequently caused by earthquakes. Within the frames of this paper, special emphasis will be put on RC bu...

The main objective of CRISIS is to provide a qualitative basis for the development of a collaborative approach to prevention and preparedness for disaster risks and management in cross-border countries located in the Western Balkan Region, which is populated with more than half a million inhabitants. The project activities comprise of: (1) seismic...

The focus of the research in this work is the application of innovative materials for the rehabilitation and reinforcement of RC columns of buildings in seismically active regions such as the Balkan region. In order to present the possibilities and advantages of the use of these materials, the Institute of Earthquake Engineering and Engineering Sei...

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 state-of-the-art seismic codes are encouraging including SSI for structures with considerable p-Δ effects and mid to high-rise b...

The structural response due to the seismic load depends on the dynamic structural properties and incoming ground motion. Although for low amplitude ground motions the material behaviour is assumed to be linear, as the amplitude increases the dynamic properties of the structures are changed so that the nonlinear effects should be considered. In dete...

Retaining structures in R. of North Macedonia until recently were only designed according to the concept of global safety factors, with the conventional methods of limit equilibrium. This method was widely used in ex-YU countries until Eurocodes have been published аs regulations in the country formal legislation, where there are prescribed differe...

This paper aims to describe the CRISIS web-based platform (WBP) in all its parts and functionalities. The platform is the main result of the two-year EU-funded project CRISIS (Comprehensive RISk assessment of basic services and transport InfraStructure). It has been developed by EUCENTRE (European Centre for Training and Research in Earthquake Engi...

Drained triaxial monotonic test is one of the most frequently used experiments in geotechnical engineering, mostly because its results are starting points for many research topics. This paper presents triaxial drained monotonic experiments on natural sand borrowed from the terraces of river Vardar, that passes through Skopje. This Skopje sand is hi...

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 invest...

The Location Tower is one of the three sites from the 3D seismic network originally installed in the 80’s which is recently re-established and enabled for real-time monitoring and recording acceleration data. The Location Tower is consisted of one surface and three downhole instruments up to 125 meters down the bedrock; a nine story building with t...

The potentially high vulnerability and poor performance of the existing buildings, after past seismic events, including exploitation period has raised awareness of the need to improve their seismic performance. Repair and strengthening gives new life to existing or ageing structures that might otherwise be demolished and replaced. This paper will a...

It is a usual practice that traditional methods with traditional materials (most frequently jacketing of elements) are used for repair and strengthening of structures. However, lately, particularly in the last two decades, there have occurred new construction materials intended for strengthening and design referred to as composites strengthened by...

For the purpose of building a new electric power facility a project to determine seismic potential and seismic parameters for design is produced. Multiple in-situ geophysical investigations have been performed and soil samples have been taken to the laboratory where simple shear tests are done to determine the dynamic parameters of the soil layers....

Continuous safe and low-cost operation of structures extensively depends on their proper maintenance and management. To apply optimal management strategies for the existing structures, accurate assessment of their present and future safety is important and crucial. Hence, monitoring of structures can be considered a necessary condition for providin...

The earthquake that took place at 03:56 local time on November 26, 2019, with Mw = 6.4, struck the west part of Albania and caused heavy damages to many public and residential buildings in the districts of Durres, Tirana, Lezha, Shkodra, Diver, Berat and the surrounding areas. Immediately after the earthquake, teams from the Institute of Earthquake...

This paper presents the harmonized approach for landslide susceptibility and hazard assessment at the cross-border region between N. Macedonia, Albania, and Greece. The European ELsusv2 initiative is selected as a harmonized approach for regional landslide susceptibility mapping for the area study. The peak ground acceleration value within the slid...

This paper presents the harmonized approach for landslide susceptibility and hazard assessment at the cross-border region between North Macedonia, Albania, and Greece. The European ELsusv2 initiative is selected as a harmonized approach for regional landslide susceptibility mapping for the area study. An analytical relationship is used to assess th...

Based on the elastic theory assumptions and averaging theories, an infinite element boundary which is frequency independent is derived for saturated soil media. The infinite element development is based on mapping functions and viscous layers for damping propagating waves of both solid and water phases. The newly developed infinite element is able...

Presented in this paper are investigations related to local site conditions carried out for seismic assessment of two historical structures in Macedonia: the Church of the Holy Mother of God Peribleptos dating back to the 13th Century and located in the old town of Ohrid, and the Mustafa Pasha Mosque in Skopje dating back to the 15th Century. The o...

The need for repairing and strengthening RC buildings and their structural elements occurs when their elements do not possess sufficient strength, stiffness, and/or ductility due to damage mostly caused by earthquakes. Within the scope of this study, special emphasis will be given to RC buildings where the built-in concrete has not achieved the des...

The aim of this paper is to present a mathematical framework and its corresponding coupled finite element discretization for fully saturated porous media. The model is developed as a coupled displacement‐pressure formulation in which the porous medium is composed of a soil skeleton and water in the pores. The considered problem in this paper is the...

Many successful applications of numerical models for simulation of sand behavior show the importance of both triaxial tests and the constitutive relations used in simulation. In this work several triaxial tests have been simulated using the hypoplastic material model. The triaxial monotonic tests have been performed at the Laboratory for Geodynamic...

This paper presents an application of the SPT based liquefaction triggering models (both deterministic and probabilistic) proposed by Boulanger and Idriss (2010). Several authors consider deterministic approaches to be beneficial in areas of high seismicity. The procedure for predicting probability of liquefaction however can be alternative tool of...

Considering liquefaction as one of the geotechnical instabilities (problems), which increase damages during strong earthquakes, there are different approaches available for assessment of its potential. The study presents the investigations and results on the evaluation of the potential of liquefiable soil layers at location where new business ‐ res...

From the detailed experimental series of 1‐G laminar box experiments on Skopje sand it was clear that additional model tests were needed having similar initial conditions as the examined sand in the laminar box. Series of index experiments on a new shipment of sand are performed to determine mechanical properties and to prove the sample consistency...

In this paper, a two-level multi-group approach to seismic performance assessment of existing building stock is presented and discussed. The first level of assessment is a simple visual screening based on the principles originally developed in FEMA (Rapid visual screening of buildings for potential seismic hazards: a handbook—FEMA 154 and 155, Appl...

Based on the elastic theory assumptions, an infinite element boundary which is frequency independent is derived. The infinite element development is based on mapping functions and viscous layer for damping propagating waves. In numerical modelling the general finite element software ANSYS using its User Programmable Features (UPF) is used. Related...

In this paper, a coupled multiphase model considering both non-linearities of water retention curves and solid state modeling is proposed. The solid displacements and the pressures of both water and air phases are unknowns of the proposed model. The finite element method is used to solve the governing differential equations. The proposed method is...

This paper presents the influence of boundary conditions in numerical simulation of soilstructure interaction problems. It discusses aspects related to a seismic load influencing a soil medium and a frame structure resting on the soil. The soil conditions are represented by 30 m soft, medium, and dense soil deposits with four layers resting on bedr...

It is common practice to design the fundaments of structures by using the Winkler method. It is the method that uses an averaged coefficient that simulates all soil layers and is derived from previous in – situ soil investigations. The subject of this paper is to compare the results of three models – one designed with the above mentioned Winkler mo...

High-rise buildings are designed and constructed by use of modern materials and integral structural systems which are not usual for typical buildings. The existing seismic regulations act as a limiting factor and cannot cover specific behaviour of these buildings. Considering the increasing trend in their construction worldwide, additional investig...

In numerical simulation of soil media, the problem of wave propagation is of a great importance. Proposed in this paper is a new formulation of infinite elements which can be used in numerical simulation of wave propagation problems in infinite domains. In numerical simulation of wave propagation, the finite elements are used to model the near fiel...

In conditions of increasing construction of building extensions in Republic of Macedonia, particularly for the last two decades, the issue of seismic stability and safety of such new “hybrid” structures is posed as an imperative. With the undertakings of different type of reconstructions, building enlargements, adaptations, etc. of existing structu...

Capacity Spectrum Method (CSM) is a current design tool to predict peak seismic performance of 2D and 3D structures. The general idea of the method can be extended including the influence of soil deformations on capacity spectrum. The design seismic action is implemented through acceleration-displacement spectrum provided by EN 1998-1. The seismic...

The experience from the occurred earthquakes and performed investigations show that the effect of the infill can be different – favorable (when the structural system has low resistance) and unfavorable (short column effect, shear failure of joints, global instability of the system – “soft” storey mechanism etc.). Тaking into account the fact that i...