New Zealand's Bridges: ANZAC Bridge across the Avon River in Christchurch (2)

March 2011 (-43.501 Degrees, 172.701 Degrees) ANZAC Bridge

The ANZAC Bridge has a 3-span voided slab superstructure on 4 column bents. It was built in 2000 and has a precast superstructure, precast bent caps, and precast columns. That makes it a very innovative design. However, the seismic design isn't easy to understand. It appears that the bridge was meant to survive the earthquake through brute strength. There are no dampers or plastic hinges designed to limit the seismic force. Moreover, the columns are too big to be damaged and so most of the damage was due to shear at the bent caps or at the column to bent cap connections. Bridges are supposed to be weaker in flexure than in shear to avoid catastrophic collapse in case the earthquake force is larger than expected. 

New Zealand's Bridges: ANZAC Bridge across the Avon River in Christchurch (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

New Zealand's Bridges: ANZAC Bridge across the Avon River in Christchurch (1)

March 2011 (-43.501 Degrees, 172.701 Degrees) ANZAC Bridge

We are nearing the end of the Avon River and its beginning to suggest the salt water environment that it will become a few miles downstream. This is another ANZAC Bridge, dedicated to the many soldiers from Australia and New Zealand who bravely laid down their lives during WWI. New Zealand seems like a place where patriotism and religion are still very important. Also sports and meat pies.

The ANZAC Bridge was one of the newest bridges on the Avon and also one of the most damaged during the recent earthquakes. It's a totally precast structure and so the bridge has some of the seismic problems that we are currently trying to solve in California: how to design a precast bridge with super strong connections and predetermined locations where damage can occur. This is a problem that Park and Pauley at the University of Canterbury worked on in the 1980s. Of course, this bridge is still standing, which is good, but the damage suggests that it might have failed in shear had the earthquake been a little bigger. We'll take a closer look at it tomorrow.

New Zealand's Bridges: ANZAC Bridge across the Avon River in Christchurch (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

New Zealand's Bridges: Avondale Bridge across the Avon River in Christchurch

March 2011 (-43.500 Degrees, 172.688 Degrees) Avondale Bridge

The next road bridge is several miles further downstream. The Avondale Bridge was built in 1962 with a precast voided slab superstructure on three column bents and seat-type abutments. A water main carried by this bridge broke during the earthquake washing out the embankment and so they are beginning to roll out an inflatable cofferdam on the opposite bank to repair the abutment.

New Zealand's Bridges: Avondale Bridge across the Avon River in Christchurch by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.