ABSTRACT
Since the mid 1970s, heavy haul railway infrastructure has been a crucial asset for South Africa with iron ore and coal being the leading commodities exported worldwide. Over the past four decades, on the one hand, a continuous higher demand of railway capacity has resulted in a significant increase in traffic volume. Thus, the operating condition of railway bridges on existing heavy haul lines has changed dramatically. On the other hand, a progressive depletion of the coal deposits extracted since the 1970s has led to the discovery of new mines in North-Eastern South Africa that need to be linked to the existing heavy haul railway network. A possible cost-effective way to do that consists of upgrading existing general freight railway lines to heavy haul transport. However, existing bridges serving those lines need then to be investigated against the new expected railway loads. The paper shows and discusses, through two different case studies, how dynamic testing and modal analysis in operating conditions can be reliable and cost-effective tools to assess the dynamic behaviour of existing bridges within performance evaluation programs.
