Arch action model applied to existing prestressed concrete bridges in Germany

In Germany, older prestressed concrete bridges are currently being assessed based on a recalculation on the basis of the structural assessment provision for existing road bridges. To determine the shear and torsional resistance, the provision comprises modified and extended design approaches in comparison to the current regulations of DIN EN 1992-2:2013. These approaches take the characteristics of existing structures into account. However, high deficits in terms of the shear capacity often remain. In order to reduce the extent of strengthening measures or to avoid premature replacement by new structures in such cases, the structural assessment provision allows the use of verified scientific procedures which consider potential load-bearing capacities not taken into account by the idealised standard design methods of the current German design code. The current design format for verifying shear capacity in Germany is based on a parallel truss model with aggregate interlock. Depending on the system, cross-section and loading, this model may exhibit considerable load-bearing reserves for prestressed beams. This paper demonstrates the application of the arch action model by examples of two structures. In addition to the shear resistance of the truss model, the arching effect of the concrete due to prestressing and bending is taken into account.