The effect of proof over-pressure on pipeline structural integrity using fracture mechanics parameters is analysed in the case of pipeline in Reversed Hydro Power Plant, made of High Strength Low Alloyed steel with 800 MPa tensile strength due to special design requirements. To assess its structural integrity, extensive testing of the full-scale prototype had been performed, including hydrostatic pressurizing. Since plastic strain was recorded during proof over-pressurizing, special attention is given to the fact that this is actually a mechanism for crack initiation and propagation. To investigate this effect micromechanical modelling is considered, as well as the Failure Assessment Diagramme. It is shown that over-pressuring has potential detrimental effect on pipeline safety, i.e. structural integrity.

No abstract

During the process of socialist modernization, initiated after WWII, large development projects in Serbia were the main drivers of urban transformation. Electrification and industrialization resulted in the establishment of new production modes, which defined a new socioeconomic background for the development of settlements and the modification of their functional and morphological structure. The construction of the Bajina Bašta hydroelectric power station, in the middle section of the Drina River in western Serbia, was one of the development projects, and it triggered the transformation of the environment, upgrading the prewar small town of Bajina Bašta into a new urban node, adjusted to the socialist imperatives and standards of progress.

In recent years, there have been numerous studies and pilot-projects both in Serbia and around the world, dealing with on-line learning. This paper analyzes the possibilities of online learning theoretically and empirically. The theoretical section presents an analysis of differences between traditional and on-line learning based on a review of the literature. The empirical study was carried out using a questionnaire distributed through various internet platforms in April 2020. The survey comprised 339 high school students in Serbia who attended on-line classes during the state of emergency imposed due to the Covid-19 pandemic. The data thus collected were processed using qualitative analysis. The aim of the study was to identify the advantages of on-line learning relative to the traditional model of instruction from the perspective of secondary school students, and to offer recommendations for further research and improvements in practice. The results of the study suggest that secondary school students in Serbia recognize the advantages of on-line learning in terms of time efficiency, the possibility to manage the learning process and improvement of the results of the instructional process.

Risk based analysis of reverse hydro power plant penstock structural integrity is performed using fracture mechanics parameters. To assess its structural integrity, extensive testing of the full-scale prototype had been performed, including hydrostatic over-pressurizing, during the design phase. More recently, the Failure Assessment Diagram has been used to evaluate probability, whereas phenomenological analysis has been used to estimate consequence, in the scope of common risk estimation. It is shown that over-pressuring has potential detrimental effect on pipeline safety, i.e. structural integrity.