Matrisk analyzed the bearings of the Aarebrücke Arch motorway bridge N5/3BS30 for ASTRA and assessed their reliability.

The starting point was calculated uplift forces from standard load models. The installed bearings cannot structurally withstand these forces. At the same time, inspections revealed no damage to the structure. This resulted in a clear discrepancy between the model and reality.

The project aimed for a realistic and data-driven assessment of bearing stress. Therefore, Matrisk developed a probabilistic traffic model that specifically accounts for uncertainties. The model integrates vehicle types, axle loads, and traffic flow. It also simulates different traffic conditions such as normal operation, congestion, and breakdowns.

Matrisk then linked the traffic loads to an existing structural model. The team used influence lines to efficiently calculate the bearing forces. In addition, Matrisk performed Monte Carlo simulations and determined hourly and annual extreme values.

Based on this, Matrisk calculated the probability of bearing failure and compared it with the target values according to SIA 269. The results clearly show that no critical load conditions occur. At the same time, the existing bearings meet the required safety levels.

The project demonstrates how real-world traffic data and probabilistic models can be combined. This allows for the targeted testing of conservative assumptions and, at the same time, enables well-founded, risk-based decisions to be made regarding existing infrastructure.