The Department of Transport Systems and Road and Bridge Construction (TS&RBC) continues research into steel-reinforced concrete constructions of superstructures under conditions of incomplete compatibility between steel beams and reinforced concrete slabs.

Although composite superstructures are now widely used in medium- and large-scale bridge projects, their calculation methodology has not been fully developed. In particular, one of the remaining open questions is the adequate analysis of connecting elements—one of the most important components of a composite structure that ensures the combined performance of the slab and beam.

The standard engineering approach, enshrined in both Russian and international design standards, assumes the connection between the slab and beam via connecting elements to be absolutely rigid in shear, which is rarely achieved in practice. While such a simplification is acceptable for new bridges, it appears inappropriate for existing structures or for assessing the durability of new bridges.

Associate Professor at the Department of TS&RBC, Nikolay Kozak, proposes evaluating steel-reinforced concrete structures using a method that takes into account the gradual decrease in the shear stiffness of the connecting elements, which depends on the process of accumulation of fatigue damage.

The general concept of the methodology includes an iterative calculation of structures with the determination of the level of damage accumulation in the elements of the connection and updating their rigidities (the concept is shown in the figure).

Today, the department's staff, including both faculty and students, is conducting research to develop methods for determining components such as:

• models for reducing the rigidity of connecting elements;
• a model of the calculated load based on actual traffic data;
• methods for determining reliability indicators.

The research is being carried out within the 2025 internal grants projects by the research and teaching staff of SPbGASU.