Introduction. Many bridge structures worldwide were designed in accordance with outdated standards and no longer meet the demands of modern transport loads. This creates a global safety issue, making the development of effective solutions for their strengthening a critically important task.
Problem Statement. he vast majority of the global bridge infrastructure, particularly in developing countries, was constructed in the mid-20th century. The design of these structures was based on the normative loads of that time, which were significantly lower than current ones. Today, the increase in traffic intensity and the emergence of oversized and heavy-duty vehicles lead to bridge overloading. This causes premature physical wear of the structures, the appearance of cracks, a reduction in their load-bearing capacity, and, consequently, poses a safety threat to all road users.
Materials and methods. The methodology of this study is based on a comprehensive approach that combines theoretical analysis, mathematical modeling, and numerical calculations. The purpose of using these selected methods is to substantiate the need for strengthening existing reinforced concrete bridge structures and to prove the effectiveness of external prestressed reinforcement compared to traditional solutions. The research is based on the Finite Element Method (FEM). This numerical method allows for approximating the behavior of a complex structure by dividing it into a set of simple elements (finite elements). This makes it possible to accurately determine the stress-strain state of the entire object. The calculations were performed using the licensed software package LIRA-SAPR, a modern tool for modeling, analyzing, and designing building structures.
Objective. To assess the effectiveness of external prestressed reinforcement in improving the durability of reinforced concrete bridge structures based on experimental data.
Results. The analysis confirmed that the existing structures have a significant strength deficit: the calculated bending moment from modern loads (184 tm) exceeds the load-bearing capacity of the existing beams (141 tm). It was found that both strengthening methods—with ordinary and prestressed reinforcement—effectively increase the load-bearing capacity of the structures, bringing it up to 193 tm and 215 tm, respectively. The use of external prestressing significantly improved the operational characteristics of the structure. The calculated deflection from self-weight decreased from 21.3 mm to 14.1 mm, and the compressive stresses in the concrete eliminated the risk of crack formation.
Conclusions. Based on the conducted calculation of forces, displacements, and comparative analysis, it was established that existing reinforced concrete bridge span beams, designed with outdated standards, have a significant deficit in load-bearing capacity and do not meet modern safety requirements. The quantitative analysis confirmed that strengthening the structures with additional reinforcement is an effective solution for increasing their strength. However, the comparative analysis showed that the method of strengthening with external prestressed reinforcement is the most appropriate, as it not only provides a significant increase in load-bearing capacity but also considerably improves the stiffness and crack resistance of the structure, which substantially extends its service life and reduces future maintenance costs. Thus, the results of this study provide a scientific and engineering justification for selecting the optimal method for modernizing typical reinforced concrete bridge structures.
