Structural Health Monitoring of Older Bridges: Current Studies in Australia and Worldwide

Iron, steel and timber bridges were built extensively in the last half of the 19th and early part of the 20th Century. Many of these bridges are now deteriorating and becoming potentially unsafe. There is a need and an opportunity for engineers to analyse the methods and procedures necessary to ensure a responsible balance between structural safety of these bridges, their economy and forward planning for rehabilitation of these bridges. It is difficult to determine the load-carrying capacity of degraded bridges in order to subsequently assess suitable designs for more economic and efficient repairs and maintenance versus replacement. Static load testing has often been the main method to quantify the acceptable load capacity of structures such as timber bridge girders, but it can be expensive. Therefore, there is justification to develop a low-cost, non-destructive evaluation (NDE) that can be used to identify the load-carrying capacity of older bridges in order to identify alternative maintenance and repair strategies. Some attempts in this direction have been made in the past. One of the objectives of Structural Health Monitoring (SHM) is to ensure the safety and reliability of an engineering system for specified functions and loading conditions over a given period of time. Structural safety and reliability become the key issues in the whole process of evaluation. Reliability assessment of the design of structural members and systems has received a great deal of attention by researchers in the last decade and many methods have been developed. A number of selected studies on older bridges in terms of structural health monitoring in Australia and worldwide are presented.