MEASURING DYNAMIC IMPACTON AGED TIMBER BRIDGES; SOME EXPERIMENTAL OPTIONS John Moore 1,* , Saeed Mahini 1 1 Department of Civil Engineering, University of New England, Armidale, NSW *Email: jmoore30@une.edu.au ABSTRACT There are thousands of aged timber beam bridges on local roads in New South Wales (NSW) and because of deterioration their safety levels are unknown. To identify a bridge safety level requires structural performance measurement, preferably with a Structural Health Monitoring (SHM) system, so that any significant temporal change can be quickly identified. There is a need, however, to identify sensors and systems that can be used to monitor the dynamic impact of loads moving at highway speeds that are of adequate performance and of a cost that is a small fraction of the structures’ value. Three measurement systems are considered: a high speed camera system to enable the establishment of base-line performance; a laser sensor system to enable accurate validation of other measurement systems on in-service structures; and a system comprising accelerometers to provide a relative motion record of components compared to the motion of a main girder. KEYWORDS Aged timber beam bridge, dynamic impact, mid-span deflection, laser, high speed camera, accelerometer. INTRODUCTION In the 19 th and 20 th centuries thousands of timber beam bridges were built on local roads in New South Wales (NSW) Australia; hundreds of thousands worldwide. Over two thousand are extant on local roads in NSW (Roorda, 2006); one example is Horton’s Creek bridge on the Armidale Grafton road in NSW as shown in Figure 1, and another is Munsies Bridge as shown in Figure 2. Both of these structures carry some heavy loads and numerous light loads daily. Many have an unknown level of deterioration and their safety levels are unknown (Howard, 2009). Economic maintenance of these bridges is, therefore, an ongoing concern for the owners of regional bridges. Figure 1: Hortons Creek Bridge, Armidale Road, NSW 214