Markovski, Goran
Preferred name
Markovski, Goran
Official Name
Markovski, Goran
Main Affiliation
Email
markovski@gf.ukim.edu.mk
11 results
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Item type:Publication, Influence of the residual tensile strength on the factor for quasi-permanent value of a variable action ψ2(Springer, Cham, 2021); ; ; Mark, PeterSteel fibres are known to aid in deflection control, control the process of cracking and mainly improve the toughness of structural elements and the whole structure. Large experimental program was performed at the Faculty of Civil Engineering-Skopje to find out how steel fibres and the residual tensile strength affect the time-dependent deformation properties and deflections of concrete. Specific realistic loading with permanent and repeated variable loads in loading interval of 8 h per day was applied on full scale beams that were monitored up to an age of concrete of 400 days. The beams were with cross section dimensions 15/28 cm and total length of 300 cm, manufactured from concrete class C30/37. They were reinforced with same percentage of longitudinal and shear reinforcement, but with different amount of steel fibres (0, 30 kg/m3 and 60 kg/m3). Using the experimental results, detailed analysis of the time-dependent deformation properties of concrete and their effect on the time-dependent behaviour was done. A value for the factor for quasi-permanent value of variable action ψ2 is proposed for each type of concrete. It was concluded that the factor for quasi-permanent value of a variable action ψ2 depends linearly on the residual tensile strength. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Application of different methods for determination of the dynamic amplification factor (DAF) from moving loads on roadway RC bridges(Springer Nature Switzerland AG 2022, 2022); ; The dynamic effect of traffic loads on roadway bridges is usually introduced through the so-called dynamic amplification factor - DAF. This parameter shows how many times the impacts obtained from the load's static action are increased. One of the main goals of the dynamic tests of reinforced concrete bridges, with proof load, is to determine the DAF's actual value and compare it with the value taken into consideration in the design project. This research focuses on the possible methods for the determination of the DAF on roadway reinforced concrete bridges. For this purpose, results of dynamic tests performed on newly built bridges, with proof loading on various motorway sections in the Republic of North Macedonia, were used. Therefore, semi-prefabricated buildings with pre-stressed concrete beam girders and a static system - simple beam were analyzed. During the test, the main girders' vertical displacements were measured, through which the DAF was determined. For processing, analysis, and filtering of the measured signals' dynamic component, appropriate techniques have been used. After processing the signals, the DAF's value is determined by applying two proposed methods. With the processed results, a comparative analysis is performed between the DAF's determined values obtained from applying different methods. These analyses allow us to study the impact of using different measurement techniques and methods for processing the signals for calculating the dynamic effect of the moving loads. In this way, an attempt is made to suggest which methods for determining the DAF obtain more reliable results for its value. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Overview of standards for static and dynamic proof load testing of RC bridges(Macedonian Association of Structural Engineers (MASE), 2022); ; The primary purpose of the testing of structures with proof load is to obtain data on their actual load-bearing capacity, stability, serviceability, as well as on other parameters of their behaviour, ie., on the compliance of the constructed structure with the used numerical model. In addition, such testing can be a final control (confirmation) of the quality of the newly built buildings. Bridges are one of the structures that, depending on their purpose and span, are subject to proof load testing, which depending on the way the load is applied, can be static and dynamic. As a prerequisite for performing a quality test, it is necessary to follow and apply standardized procedures, including a quality test program and the application of precise, calibrated measuring equipment. The neglect of these procedures leads to doubts about the measured results' reliability and usability. This paper first focuses on reinforced concrete bridges' static and dynamic proof load testing procedures. The specific aspects of the proof load testing are then presented, with an overview of the necessary previous work to be done before starting the test, determining the intensity of the proof load, the procedures that follow during the test process, and the post-processing of the measured results and their analysis. Based on the performed review and systematization of the procedures for examination with proof load, as well as the experiences gained from examination of a large number of real scale objects, in the end, specific procedures and practical recommendations for conducting this type of examination are proposed. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Monitoring based structural identification of two railway bridges(Faculty of Civil Engineering Skopje, 2020-07); ; Data-driven tools applied on measured structural responses enable extraction of valuable information on the behavior of in-service structures and identification of the actual system in its “natural habitat”. An output-only testing campaign on two railway bridges is in the focus of this study. The specifics of the dynamic behavior of the structures are studied under three different scenarios. More precisely, the measured accelerations at relevant points of the structures, for unloaded and loaded conditions, are herein employed with the following objectives: I) Structural dynamics identification via estimation of the first natural bending frequency of the structures during ambient unloaded conditions using the AutoRegressive Moving Average (ARMA) method and the time-domain Subspace System Identification (SSI) method; II) Assessment of traffic safety aspects based on the maximal amplitudes of vibrations during loaded operating conditions of the structure, for two separate train induced vibrations (train velocity of 40 km/h and 60 km/h); III) Evaluation of the dynamic effects through a dynamic amplification factor estimated from the recorded responses during dynamically loaded structure (train velocity of 40 km/h and 60 km/h). By utilization of the response-based data analysis methods the first natural frequencies of the steel structures are successfully identified and compared with FEM numerical results. The acceleration data is further assessed by preprocessing filtering techniques and extracted features are assessed according to EN 1990:2002 or UIC (International Union of Railways) code 776-2 (2009). - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Crack width control in RC beams: experimental and analytical results(Macedonian Association of Structural Engineers (MASE), 2022); ; In order to satisfy the required level of reliability, the structure has to be designed so none of the ultimate and serviceability limit states will be reached within the expected service life. By undertaking measures for ensuring the required durability, its serviceability is directly affected, as well as its load-bearing capacity, which may be endangered due to the dilapidation of the structure. Limitation of crack width and the adequately provided concrete cover, which primarily lead to corrosion protection of steel reinforcement, are one of the basic and maybe the most important preconditions for ensuring the required durability. Despite the wide range of knowledge gained through numerous experimental and theoretical studies, there are still certain dilemmas regarding the implementation of models given in the codes for crack control. In order to determine the influence of long-term sustained load on the serviceability limit state-crack control and to estimate the level of accuracy of the considered analytical models, an experimental program on RC beams was realized. Eight beams with dimensions 15/28/300cm were made and monitored in a laboratory environment with constant ambient conditions. This paper presents formation and development of the cracks in the considered time period of one year. An overview of the obtained results using several modern analytical models for crack prediction is also provided. In this paper, the results show that the modern analytical models given in the standards with satisfactory accuracy can predict the serviceability limit state-crack control due to long-term load. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Reliability assessment of the superstructure of precast prestressed bridges(Macedonian Association of Structural Engineers (MASE), 2022); ; Given that all buildings are designed for a certain "lifespan", there comes a time when the question must be asked whether they are still safe and serviceable? The need to ask this question arises from the fact that over time, each object is exposed to external influences and suffers certain geometric and material degradations, mechanical damage, increased intensity of moving load (weight and frequency of vehicles), and also the production and control of materials was then at a lower level. The answer to this question can only be revealed through their research and reliability assessment, and the final answer can be: demolition and reconstruction, repairing and / or strengthening, no interventions required. Reliability is the probability that a system (construction) will perform the functions for which it is designed during a certain time interval ("lifespan") under specific operating conditions. In order to determine the reliability index of the structure (βsystem), the reliability indices at the level of the structural element (βi) should be determined first, and then through their connection (depending on the structural system and the limit states) the reliability of structure is determined. Due to the lack of means and conditions to examine the necessary geometric, material and other data for an old bridge, a reliability assessment was performed on a relatively new bridge, i.e. reinforced concrete pre-stressed girder overpass on the highway section Miladinovci - Stip. For that purpose, the project of the same was used, as well as all available reports on the embedded materials that are of particular use for modeling the real model. Reliability is examined in terms of ultimate limit state (flexural moments) using FORM (First Order Reliability Method) and MonteCarlo simulation technique. At the end of the paper, a comparative analysis is performed between the results of the two methods with the recommended minimum values in EN1990 [1] for a 1 year reference period. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Cracks in reinforced concrete structures due to restrained imposed deformations – case studies(Macedonian Association of Structural Engineers (MASE), 2022); ; ; - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Sulfate resistance of cement with different volumes of fly ash(Slovenian National Building and Civil Engineering Institute (ZAG), 2020); ; SUMMARY: Sulfate attack is a complex severe set of chemical and physical processes that have great influence on concrete durability by changing the microstructure of the cement paste and concrete. Sulfate resistance of concrete should be obtained including requirements for low-permeability concrete, use of sulfate resistance cement and proper production of concrete. In this paper an extensive experimental research is presented on the possibility of using fly ash as a partial replacement of OPC clinker and its influence on the sulfate resistance of cement. For that purpose, four samples of fly ash from the TPP Bitola were taken in the time period of two weeks. All cement components including fly ash were completely tested from the aspect of chemical composition and physical properties. Two samples of fly ash which showed the biggest difference in their fineness were chosen for further investigations and preparation of cements. Laboratory cements were prepared by varying the quantity of fly ash as replacement of OPC clinker, from 0% to 50%. For all laboratory produced cements complete chemical analysis and determination of the physical and mechanical properties have been carried out. The method of Koch & Steinegger and the recommendations of the Technical Committee of Cement given in CEN/TR 15697 were used for determination of sulfate resistance of the laboratory cements. According to this method, small specimens (prisms with dimensions 10/10/60mm) were prepared and then cured in deionized water and aggressive solution – 4.4% Na2SO4. The corrosion coefficient calculated on the basis of flexural strength of the specimens tested after 56 days in aggressive solution was used as indicator of sulfate resistance of the cements. On the basis of the test results, it is determined that the fly ash and all laboratory cements fulfil the quality criteria defined in the standards. It is also concluded that the cements with 30% fly ash show the best results from the aspect of sulfate resistance. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Analysis of second-order effects according to Eurocode 2(Macedonian Association of Structural Engineers (MASE), 2022); ; ; The Eurocode, as the current design code in our country, allows designing objects according to contemporary standards but also opens a great number of research topics. The focus of this paper will be the two simplified methods that Eurocode 2 offers for the calculation of the second-order effects, which are particularly important when designing construction elements with great height or with large longitudinal forces. The second-order moments will be calculated for columns by varying a larger number of factors that, less or more, influence the final results. Thereby, the two simplified methods in Eurocode 2, method of nominal stiffness and method of nominal curvature, will be applied and compared. The main goal is to determine how the change of some factors, like: effective length, concrete class, cross-section, stiffness of the elements which is connected with the cracks, affects the second-order moments calculated with the two methods. These analysеs will be conducted in 6 key studies for isolated columns. The key studies will determine the actual influence that the second-order moments have. From the calculations made with the two methods different results for the moments are obtained, but to a certain value, the results are with an insignificant difference. The reason why the method of nominal stiffness and the method of nominal curvature give different results will be explained and the point at which they give approximate results will be determined. In the conclusions, everything that has been determined within the analyses will be highlighted. Given that Eurocode 2 leaves the opportunity to choose the method of analysis of the second-order effects up to the country’s National Annex, with the analyses made a contribution to that decision was made, with a conclusion which method is more appropriate for calculating the second-order effects. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Dynamic Behaviour of RC Bridges Under Moving Loads: A Simplified Numerical and Analytical Approach(Macedonian Association of Structural Engineers (MASE), 2023); ; ; Mark, PeterUsing numerical and analytical modelling of the dynamic behaviour of concrete bridges subjected to moving loads is essential for ensuring their structural safety and durability. This topic aims to investigate the impact of moving loads on the dynamic behaviour of concrete bridges and to identify simplified methods for accurately evaluating their response. This research addresses the practical necessity for simple, reliable and efficient methods for monitoring the structural integrity of concrete bridges under traffic loading conditions. A range of research methodologies can be utilised to evaluate the dynamic behaviour of concrete bridges under the influence of moving loads. These may encompass numerical modelling techniques such as Vehicle-Bridge-Interaction (VBI) and analytical techniques such as Response Surface Methodology (RSM). VBI entails simulating the interaction between moving vehicles and bridge structures to assess their dynamic response. RSM involves creating a meta-model for predicting the response of bridge structures subjected to various parameters of interest, including bridge span, pavement condition, the velocity of moving vehicles, their trajectory, and the weight and number of axles of vehicles. Sensitivity analysis can subsequently be employed to identify the most critical parameter that influences the response. One of the possible responses for evaluating the dynamic behaviour of bridge structures is the Dynamic Amplification Factor (DAF). This factor indicates the increase in effects caused by the dynamic action of the load. In other words, it shows how many times the static effects are amplified due to dynamic behaviour. A crucial finding of this research is that many interrelated factors influence the dynamic response of concrete bridges to moving loads. These may encompass the bridge's design and its properties, material properties, condition, and the moving loads' characteristics. Hence there is need for a combination of numerical and analytical modelling. Each methodology has advantages and limitations, and a comprehensive assessment of a bridge's dynamic behaviour requires multiple approaches. Evaluating the dynamic behaviour of concrete bridges under the influence of moving loads is a complex undertaking that necessitates a multi-dimensional approach. By integrating numerical and analytical modelling techniques such as VBI and RSM, it is possible to accurately determine the impact of moving loads on bridge structures and ensure their structural safety and durability.