-42- 
members and is approximately 190 m in length. A stringer is a 
horizontal member that transfers load to vertical members—see 
Figure 5. Each stringer was approximately 6 m long with a 
diameter of 500 mm. The structure has been reinforced with 
steel beams in several locations where wooden members have 
rotted or been destroyed by termites. A pre-stressed concrete 
bridge now takes the traffic load over the Avon River and, at the 
time of writing (May 2002), dismantling of the wooden bridge 
was well underway. 
Prior to disassembly, the wooden bridge was subjected to static 
load testing on two of its spans in order to determine its strength 
and load sharing properties. Though this bridge was 
decommissioned, some 3000 bridges of similar construction 
exist within the state of Western Australia. Insight into their 
properties was sought through testing in order to determine how 
to best maintain such structures. 
4.2 Static Load Testing 
Static load testing was performed by parking a truck loaded 
with concrete and steel weights at various locations on the 
bridge. Linear-variable-differential transformers (LVDTs), 
digital photogrammetry and TLS were used to measure 
deflections and load cells installed to measure force. Data from 
these sensors would be used to infer the bridge’s mechanical 
properties. 
Five different loads were applied during testing, with the 
maximum being 65.75 t. These were placed at various locations 
(e.g., at mid-span, over columns, etc.). Testing was conducted 
on two separate days. On day one, a single 6 m-long section 
was tested with some 95 different load conditions. The time 
constraints imposed by so many tests dictated that the window 
in which photogrammetric and laser scanning measurements 
could be acquired was only 2 minutes. 
4.3 Photogrammetric Measurement 
An Olympus E20 digital camera (array size: 2572 (H) x 1920 
(V) pixels) was used to capture a convergent network of 6 
images of the targeted span. Though more would have been 
desirable, the number of images that could be captured was 
limited by the time taken to write image data to the camera’s 
memory card. The bridge was imaged prior to the application 
of each mass to obtain a no-load epoch for deformation 
analysis. Twenty Gb of imagery was captured on the first day 
of testing. 
More than 200 retro-reflective targets were rigidly fixed to 
members of the first span. These consisted of a 25 mm circle of 
retro-reflective film centred on a 50 x 50 mm piece of 
aluminium angle iron painted flat black. The camera’s flash 
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