Health assessment of road bridges with Gerber saddles: non-linear planar models

A correct assessment of the structural behavior and performance of deteriorated structures is crucial both for a proper planning of maintenance works and for a correct design of new structures in aggressive environments. The aim of this work is to investigate the response of Gerber saddles to the variation of the two main parameters representing typical damaged scenarios: the concrete cover and the diameter of the steel reinforcements. The analyses are conducted through Finite Element two-dimensional non-linear models based on the compatible stress field; the results are compared with the relevant ‘Strut and Tie’ models. At first, parametric analyses are carried out, in order to evaluate the sensitivity of load capacity to the position of steel rebars and to the dimension of concrete cover; this first part of the contribution aims to highlight the importance of an adequate level of knowledge. Then, the contribution focuses on the reduction of saddle capacity due to degradation conditions, referred to both the loss of concrete cover and the corrosion of reinforcing bars. The analyses closes with a comparison among the results provided by the two-dimensional investigations and the ones provided by the relevant ‘Strut and Tie’ models.