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Wednesday, 27 July 2011

Bridges in floods

With news reports on the Dimboola Weir this week, it harks back to the "Still going strong" post in January, when I mentioned a number of wooden bridges. Since then the flood waters have come and gone, and now the roads are open again, We've had our first chance to see the bridges on the lower reaches of the Wimmera River.

Firstly at Jeparit - as seen in the photograph above (2008) and below (2011) not much has changed, despite the township of Jeparit being surrounded by floodwater and the sandbags still on the levee bank. Maybe the corbels on the extreme left have fallen away more, but really it looks remarkably similar.

The Jeparit Bridge was built in 1892 with hewn timber corbels supported by big timber struts. It has seven main trestle and girder spans using strut & crown girder construction.




It was evident from this approach shot ^ of the Tarranyurk Bridge that this one had suffered more than the Jeparit one. It looks as if a chunk has been removed from the upstream side of the roadway. This is a bypassed road bridge west of Tarranyurk on the Tullyvea Road.

Two views of the Tarranyurk Bridge, taken from on the new bridge. In the 2008 photograph, the bowing and buckling of the deck can be seen, and now with the missing trestle the bending is more pronounced.





From under the deck, you can see the reason why the bridge fell in.

The March 2008 photograph shows that the right-hand support had already rotted through and was misaligned, and the one next to it was also extremely worn at the straight beam level.

The 2011 photo was taken from a different spot due to the higher water level and is a span further away. You can see the light coming through from the missing deck area.






At Antwerp the bypassed timber road-bridge on the Antwerp-Woorak Road, was already missing a roadway span, as evident in the 2008 picture.

This probably helped lead to the partial collapse of that section as the trestles have given way and now lean into the river, and the roadway bitumen has separated and dropped several feet from where it met the approach ramp.





A large amount of debris was piled up against the supports on both the new bridge on the upstream side, and the old bridge. The tree trunks still lodged in the old bridge attest to that, and to the height of the river level at the time.