Many of the existing highway bridges in Denmark are designed and constructed before the 1970s. The design was based on traffic load models, which do not cover the load level from modern heavy transport. In order to ensure the required level of safety, it is necessary to either replace/strengthen these bridges or alternatively to document that the existing bridges are able to carry higher loads than what they were designed for.
The overall objective of this research project is to establish a modelling framework that can document an extended service life of existing bridges and thereby reduce the expenses used on strengthening or replacement. Avoiding the replacement of existing bridges also benefits the environment and the battle against climate changes due to savings on construction materials and other replacement efforts.
In this PhD project, a framework for numerical limit analysis of slab bridges that accounts for shear-moment interaction is presented. The framework can be implemented with general optimisation solvers and can calculate the load-carrying capacity of ordinary as well as complex slab bridges accurately.
A particular type of slab bridge constructed with precast inverted T-beams and in-situ concrete is considered. Such bridges have, in the main research project, been tested, and evidence of a structural behaviour similar to that of solid slabs is found. Furthermore, a layer model within the numerical limit analysis framework is developed which accounts for the construction joints.