The honor of our university is young scientists whose research activities have high practical value. Nikolay Kozak, senior lecturer at the Department of Roads, Bridges and Tunnels, studies the reliability of bridge span structures.

Nikolay Kozak’s research allows optimizing economic costs and increasing the operational safety of a bridge structure, identifying its weak and strong points. You can try to strengthen the former to the required level, while the latter, on the contrary, can be reduced.

During his PhD studies, Nikolay Kozak did research on the endurance of elements combining a slab and a beam in the form of flexible pin stops. Then he became interested in the role of this factor in ensuring the reliability of the entire bridge structure.

Last year, Nikolay Kozak won a university grant and published two articles: one in the Russian journal Transport Structures, the other in the collection of the international congress IABSE New Delhi 2024. In these articles, he told what would happen if elements of the superstructure unification began to appear out of service. Now he is working on the article on the results of a numerical experiment in which the influence of the accumulation of fatigue damage (damage that a structure receives when exposed to frequent repeated loads) on the value of the structural reliability index was modeled.

“I am supported by the members of the department - Vladimir Apolinarievich Bystrov, Anton Vladimirovich Syrkov, Dmitry Andreevich Yaroshutin, as well as colleagues from the University of Minho (Portugal), where I had an internship in 2021. We are discussing some issues with representatives of bridge departments at other universities.”

The scientist found that the amount of accumulated fatigue damage affects the reliability index of the structure. This index is not enshrined in the Russian regulatory framework, but if we take European standards as a basis, the safety threshold may be exceeded before the required overhaul.

“The problem with modern bridge construction standards is that they do not regulate the need to take into account the accumulation of fatigue damage. And this need can be objectively substantiated only by determining the dynamics of the decrease in the reliability of the entire structure due to such accumulation,” says Nikolay Kozak.

So far all experiments are numerical. And are very resource-intensive: one probabilistic calculation can take up to a week, so the scientist uses parallel calculations on several cloud servers. But in the future I would like to conduct laboratory tests on large-scale models of spans.

Nikolay Kozak’s immediate plans include clarifying the parameters of calculation models to determine reliability indices, as well as creating probable models of traffic loads on bridges, since even in the JCSS Probabilistic Model Code (international standards for constructing probabilistic models of building structures) this issue is still not covered.