Load-bearing reserves of existing bridges

In the same way as the Technical Bending Theory (TB) for linear-elastic materials, the Extended Technical Bending Theory (ETB) makes it possible to calculate the state of strain of reinforced and pre-stressed concrete cross-sections stressed by any combination of the stress resultants M_y, M_z, T, V_z, V_yand N. When using the ETB, no additional models are required to determine the shear-bearing capacity of these cross-sections. Furthermore, the theory describes the serviceability limit state (SLS) as well as the ultimate limit state (ULS).

In the first part of the paper, the differences between the ETB and the classical calculations based on the TB and empirical truss models will be explained. Additionally, comparisons of test results and calculations with the ETB will point out convincing correspondence in SLS as well as in ULS.

In some specific cases, the more realistic results obtained using the ETB identify additional load bearing reserves in existing bridges. Because of this, the ETB sometimes makes it possible to verify the structural integrity of existing bridges even when the classical dimensioning concept has failed. As the maintenance and repair of bridges becomes more and more important, the ETB can help to keep bridges in service. In the second part of the paper, some current examples for the application of the ETB will be presented. The theory has made it possible to save several bridges without the need for expensive repair and alteration work.