Bridges

Over a bridge's service life, numerous factors can lead to an insufficient capability to meet new traffic demands. One of the most critical factors involves Over-sized and Over-mass (OSOM) vehicles that operate on our aging bridge networks, imposing much heavier loads and contributing to rising traffic volumes, far beyond what the original bridges were designed to handle. Consequently, many existing bridges are unable to withstand these increased load and traffic volume demands.

There are numerous situations where it becomes essential to strengthen an existing bridge structure to restore or improve its capacity, ensuring that the bridge remains open to legal and unrestricted loads while potentially extending its service life. Several strengthening techniques are available to help bridge asset owners and designers improve bridge capacity. These include the application of fibre-reinforced composite materials (FRP), external post-tensioning systems, near-surface mounting (NSM), embedded through sections (ETS), external vertical prestressing bars, and the enlargement of concrete sections etc. Selecting the most feasible technique at the early concept design stage is crucial for gaining acceptance from bridge asset owners for the proposed strengthening methods and preventing unexpected issues during construction.

The purpose of this paper is to provide an overview of several practical strengthening methodologies, highlighting their advantages and disadvantages for concrete girder bridges that have been successfully implemented in Australia. The methods are presented as below:

• Embedded Through Sections (ETS);
• External Vertical Prestressing Bars;
• Near Surface Mounted (NSM) systems;
• External post-tensioning systems.