Metal frame of modular collapsible wedge scaffolding: Stress-strain state under cable pre-stress

The object of research is mobile collapsible metal structures based on modular wedge scaffolding, widely used for the construction of temporary structures (stands, stage structures, enclosing walls) during mass events. This work aims to identify shortcomings in operating prefabricated metal structures based on wedge scaffolding and develop methods to improve their efficiency. The work is relevant because mobile rod systems for temporary structures are increasingly used, but their operation and the impact of joint gaps remain insufficiently studied. Method. The static analysis of the tribune fragment was performed using the LIRA-SAPR 2013 R3 software (type 5 scheme) with the use of beam finite elements (finite element type 10). The length of each element was divided into 5 equal segments (approximately 0.4 m per segment, depending on the element length). The actual semi‑rigid behaviour of the connections between the crossbeam and the deck was taken into account by assigning hinges of finite rigidity based on the bending moment diagram. The foundation was modelled as an elastic support (single‑node FE type 56 with automatic iterative calculation of subgrade reaction coefficients). The applied loading included self‑weight (γ_f =1.05), a live load of 4.0 kN/m² from spectators (γ_f =1.2), and static wind loads along the ±Y directions for terrain categories A and B. The analysis was limited to static conditions because the goal was to compare ties under primary loads; crowd dynamics are not considered and are noted as a limitation. Results. The main results of the study are as follows: using the example of the Kazanka facility (Kazan, Russian Federation), the study identified an uneven distribution of forces and the significant influence of foundation settlements. The study numerically demonstrated the high efficiency of introducing pre-stressed flexible connections (cable ties) into the rod system. The findings suggest that their use can reduce uneven support settlements by up to 42%, allow lightly loaded crossbars, and regulate force distribution. For freestanding walls, rational schemes for combining standard diagonals and ties have been developed and compared, reducing movements by 43% and metal consumption by 19%.