Wednesday, August 31, 2011

New Zealand's Bridges: Moorehouse Overbridge across Colombo Street in Christchurch (2)

March 2011 (-43.540 Degrees, 172.637 Degrees) Moorhouse Overbridge
Another view of the Moorhouse Overbridge. The material under the bridge is from sand boils that spewed wet, silty sand onto the ground. This was the only highway bridge that was closed for an extended period of time after the February earthquake.

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New Zealand's Bridges: Moorehouse Overbridge across Colombo Street in Christchurch (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Tuesday, August 30, 2011

New Zealand's Bridges: Moorehouse Overbridge across Colombo Street in Christchurch (1)

March 2011 (-43.540 Degrees, 172.637 Degrees) Moorhouse Overbridge

My last bridge from Christchurch, New Zealand is the Moorhouse Overhead. It is an eleven span T girder bridge that carries Moorhouse Avenue quickly up and over Colombo Street. It was built with split columns and expansion joints at the 1/3 points. Later, one of the expansion joints was locked up, resulting in unsymmetrical motion and a lot of damage during the February earthquake (see figure below). We'll take another look at this bridge tomorrow.
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New Zealand's Bridges: Moorehouse Overbridge across Colombo Street in Christchurch (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Monday, August 29, 2011

New Zealand's Bridges: Durham RR Overhead in Christchurch

 
March 2011 (-43.541 Degrees, 172.637 Degrees) Durham RR Overhead
Like the previously studied Colombo RR Overhead, this bridge climbs rapidly to provide sufficient clearance over the railroad. It's a long T-girder bridge on multicolumn bents. It was made continuous except for an expansion joint at the middle of the bridge (over the railway). The steep rise with an expansion joint at the top allowed the two halves to move apart during the earthquake (see figure below).
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New Zealand's Bridges: Durham RR Overhead in Christchurch by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Sunday, August 28, 2011

New Zealand's Bridges: Horotane Overbridges in Christchurch (2)

March 2011 (-43.573 Degrees, 172.695 Degrees) Horotane Overbridges
Another look at the Horotane Bridges. I think these bridges had just the right combination of sliding girders at the bent caps while being held loosely together by the rod restrainers and abutments to escape the earthquake with only moderate damage. You can see how the embankment slid towards the road. The abutments had been retrofitted with steel brackets around the I-girders but almost all the bolts sheared off (see photo below), which made nice souvenirs for our team.
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New Zealand's Bridges: Horotane Overbridges in Christchurch (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Saturday, August 27, 2011

New Zealand's Bridges: Horotane Overbridges in Christchurch (1)

March 2011 (-43.573 Degrees, 172.695 Degrees) Horotane Overbridges
Next to the Port Hills Bridges are a pair of simple span precast I girder bridges on tall hammerhead bents. The columns are tall because the road is coming down from the mountains. This made the embankments too steep (in the view of the geotechnical engineer in our group) and resulted in slope stabilty failures. Very little bridge damage, though. We observed horizontal cracks on the sides of the columns facing the street (see drawing).

We'll take another look at this bridge tomorrow.  


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New Zealand's Bridges: Horotane Overbridges in Christchurch (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Friday, August 26, 2011

New Zealand's Bridges: Port Hills Overbridges across Route 73 in Christchurch (2)

March 2011 (-43.573 Degrees, 172.695 Degrees) Port Hills Overbridges 
 
I took this photo of the Port Hills Overbridges while standing between the bridge decks.

At-grade road crossings require a stop sign, a traffic light, or a traffic circle. However, if one of the roads is an expressway you need to separate them with a bridge (or maybe a tunnel). If they are both expressways, you usually need an interchange.

Typically, to carry vehicles onto a bridge you can use mounds of earth (embankments), retaining walls (like we saw on the Colombo Street Overbridge), or the bridge can start at grade and climb steeply with short and tall piers.

However, Port Hills Road is descending from hills, so instead of an embankment, Route 73 is in a cut section below the bridge. Note the crib wall holding back the toe of the slope. As I've said before, I've seldom seem earthquake damage to this type of earth retaining structure. Also note the steel keys keeping the girders from moving transversely. At Caltrans, our philosophy is to let the bridge move, and design for the displacement.
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New Zealand's Bridges: Port Hills Overbridges across Route 73 in Christchurch (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Thursday, August 25, 2011

New Zealand's Bridges: Port Hills Overbridges across Route 73 in Christchurch (1)

March 2011 (-43.573 Degrees, 172.695 Degrees) Port Hills Overbridges
Driving south from Christhchurch to Lyttleton are these six span precast, voided slab bridges on hammerhead bents. At least one of these bridges was built in 1970 and the other may have been built later. If you look closely you can see the bridges were retrofitted with braces and brackets to hold it together during an earthquake. Another nice detail is the column by the far abutment, which is the same length as the others but isolated from the surrounding embankment with a hollow casing.
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New Zealand's Bridges: Port Hills Overbridges across Route 73 in Chirstchurch (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.



Wednesday, August 24, 2011

New Zealand's Bridges: Oxford Street Bridge into the Port of Lyttleton (2)

March (-43.605 Degrees, 172.622 Degrees) Oxford Street Bridge
Looking toward Lyttleton Harbor and the Oxford Street Bridge. 
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New Zealand's Bridges: Oxford Street Bridge into the Port of Lyttleton (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Tuesday, August 23, 2011

New Zealand's Bridges: Oxford Street Bridge into the Port of Lyttleton (1)

March (-43.605 Degrees, 172.622 Degrees) Oxford Street Bridge

We are in the port town of Lyttleton where 61% of imports and 34% of the exports to and from the South Island are handled. It is also the closest location to the February earthquake, although we could find little damage to this bridge. That unfortunately was not the case for the town of Lyttleton, which looked battered by the earthquake. 

The Oxford Street Bridge is a long, winding, steel plate girder bridge on pier walls across roads and rails that goes between the hills and the Port at Lyttleton. 
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New Zealand's Bridges: Oxford Street Bridge into the Port of Lyttleton (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Monday, August 22, 2011

New Zealand's Bridges: Colombo Street Overbridge across the railway in Christchurch

March 2011 (-43.541 Degrees, 172.637 Degrees) Colombo Street Overbridge

We'll finish our tour of Christchurch with some railway and roadway overcrossings. 

The Colombo Street Overbridge crosses over the railway in the middle of town. It is a long, continuous T-girder bridge on pier walls that was built in 1940. These types of bridges go from street level to 25 feet above the ground in as short a distance as possible and have piers of varying height. That makes the short columns susceptible to earthquake damage, although there was none during the February earthquake. Note the retaining walls at the two ends to bring the bridge down to grade.
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Sunday, August 21, 2011

New Zealand's Bridges: Chaney's Overpass in Christchurch (3)

March 2011 (-43.430 Degrees, 172.646 Degrees) Chaney's Overpass

One last photo of Chaney's Overpass. Its odd that the precast girders extend beyond the sides of the pier wall. However, the bridge deck is haunched downward to sit on the pier wall, so its actually a solid cap sitting on the wall. 

It seems like it would have been easier to have set the ends of the girder segments on the wall, but maybe it's easier to design it with the ends near the inflection points of the spans. The wall looks kind of thin to be supporting this big superstructure. Even though it is well-seated at the abutments we could see cracks in the soil where the pier foundation had moved back and forth during the earthquake.
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New Zealand's Bridges: Chaney's Overpass in Christchurch (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Saturday, August 20, 2011

New Zealand's Bridges: Chaney's Overpass in Christchurch (2)


March 2011 (-43.430 Degrees, 172.646 Degrees) Chaney's Overpass

Another look at Chaney's Overpass. There are cracks, holes, and ejected material on the ground from February's earthquake. My friend Kawashima-san (in the yellow vest) is so well-known in Japan that he brings his own film crew on earthquake investigations to record his thoughts. 

The bridge barrier rail is bolted to the underside of the deck overhang. I wonder how effective it is at deflecting vehicles? They painted the bottom half of the pier walls for some reason. Maybe it makes them less reflective to oncoming traffic at night? The barrier rails are pretty close to the pier walls. I wonder if they have rules on how close the piers can be to traffic? 

It looks like the slope paving on the far embankment has slid downward. Also, it appears that the wingwall goes straight out instead of running parallel to the roadway.
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Friday, August 19, 2011

New Zealand's Bridges: Chaney's Overpass in Christchurch (1)

March 2011 (-43.430 Degrees, 172.646 Degrees) Chaney's Overpass

There are just a few highway bridges around Christchurch. Chaney's Overpass is a three span precast box girder bridge that carries southbound Route 1 over the new road that connects northbound Route 1 to the Main North Road. 

This bridge site has some nice sand boils and other signs of liquefaction from the series of earthquakes that started in September of 2010 and has continued sporadically ever since.

New Zealand has made an art and science of building precast girder bridges that are continuous for several spans. This bridge is supported on big pier walls. If you look closely, you can see a construction joint at the top of the walls, but with the wall reinforcement continuing up into the superstructure.The girders are cantilevered over the pier walls and made continuous with drop-in spans over the road and at the abutments.

We'll take another look at this interesting bridge tomorrow.
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New Zealand's Bridges: Chaney's Overpass in Christchurch (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Thursday, August 18, 2011

New Zealand's Bridges: Groynes Footbridge in Christchurch (3)

March 2011 (-43.451 Degrees, 172.606 Degrees)
A photo of Groynes Footbridge showing the cable anchors buried in the ground.
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New Zealand's Bridges: Groynes Footbridge in Christchurch (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Wednesday, August 17, 2011

New Zealand's Bridges: Groynes Footbridge in Christchurch (2)

March 2011 (-43.451 Degrees, 172.606 Degrees) Groynes Bridge

A groyne, according to a book on 'Bridge Scour' by Melville and Coleman, is a projection into a channel to reduce flow velocities through sedimentation. There is a rocky projection on the south bank of Otukaikino Stream just to the west of this bridge; perhaps to prevent scouring around the tower legs. 
Note the rectangular steel frame a little past the tower to keeps the cables in position. The ends of the cables are swaged into eye bars that are attached to fancy turnbuckles and connected to steel rings that are cast into the anchors. This is quite different than the cables on the suspension footbridges in Ecuador that were attached to the anchors by unravelling the ends of the cables and weaving them back further up the cable to form a loop.
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New Zealand's Bridges: Groynes Footbridge in Christchurch (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Tuesday, August 16, 2011

New Zealand's Bridges: Groynes Footbridge in Christchurch (1)

March 2011 (-43.451 Degrees, 172.606 Degrees)
A steel suspension footbridge with concrete cruciform towers in 'The Groynes,' a meandering wetlands a little south of the Waimakariri River. As can be seen in the photo, the deck twisted due to the shaking during the February Earthquake. 

Every bridge has its characteristic way of responding to earthquakes. Fortunately, the shaking during this earthquake was small enough so we could see the initiation of damage at each bridge. This is better (in many ways) than when there is too much damage, which hides the evidence of how it occurred. 

We'll take another look at this bridge tomorrow.
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New Zealand's Bridges: Groynes Footbridge in Christchurch (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Monday, August 15, 2011

New Zealand's Bridges: Mandeville Footbridge across the Kaiapoi River in Christchurch (2)

March 2011 (-43.381 Degrees, 172.656 Degrees) Mandeville Footbridge

Due to frequent earthquakes during the last year this old, formerly elegant suspension bridge has become sadly disheveled. Fulton Hogan, an expert in cable bridge repairs, has begun re-tensioning the cables. The Waimakariri District Council has evaluated several approaches for the repair and hopeful they can return this symbol of Christchurch and Kaiapoi to its former attractiveness and functionality. 

Five spans with short, wooden towers and only two anchorages means these cables have to resist a lot of tension to hold up the deck without overloading the towers. Suspension footbridges are interesting structures, so we'll take a look at another one tomorrow.
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New Zealand's Bridges: Mandeville Footbridge Across the Kaiapoi River in Christchurch (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Sunday, August 14, 2011

New Zealand's Bridges: Mandeville Footbridge across the Kaiapoi River in Christchurch (1)

March 2011 (-43.381 Degrees, 172.656 Degrees) Mandeville Footbridge

The Kaiapoi River joins the Waimakariri just before it empties into the Pacific. A mile upstream from the river's mouth is the town of Kaiapoi and a five span timber suspension footbridge, During the September 2010 and the February 2011 earthquakes the banks moved towards the river carrying the bridge anchorages with them. Consequently the deck sags and the bridge was closed when I visited it. Anchorages need to be buried deeply so they aren't effected by lateral spreading during earthquakes. This bridge was built in 1874.
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New Zealand's Bridges: Mandeville Footbridge across the Kaiapoi River in Christchurch (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Saturday, August 13, 2011

New Zealand's Bridges: Old Waimakariri Highway and Railway Bridges in Christchurch

March 2011 (-43.412 Degrees, 172.651 Degrees) Old Waimakariri River Bridges
The Old Waimakariri Bridge was built in 1950. It's a steel girder bridge on pier walls that carries the Main North Road. To the east is an even older railway bridge. Note the exposed piles on both bridges. Also, the old highway bridge is carrying a big water line. The new Waimakariri Bridges are just to the west of this photo. Waimakariri is a Maori work that means something like 'river of cold rushing water.'

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New Zealand's Bridges: Old Waimakariri River Bridges in Christchurch by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Friday, August 12, 2011

New Zealand's Bridges: New Waimakariri Bridges in Christchurch

March 2011 (-43.414 Degrees, 172.646 Degrees) New Waimakariri Bridge
   
The Waimakariri River is quite a way south of this photo. Perhaps the owners of the Christchurch Northern Motorway wanted to provide the smallest possible grade for their bridges. Or maybe it was essential to provide a couple of roads north of the river. A braided river constantly regrades its path to the sea (as it drops sediment along its path). Perhaps long bridges were necessary over a river that periodically changes its channel.

The new Waimakariri River Bridges are precast I girder bridges on pier walls with very long bent caps. Perhaps the extra large caps are to accommodate a bridge widening at some future date?
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New Zealand's Bridges: New Waimakariri Bridges in Christchurch by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Wednesday, August 10, 2011

New Zealand's Bridges: Smartlea Street Bridge across the Heathcote River in Christchurch

March 2011 (-43.558 Degrees, 172.606 Degrees) Smartlea Street Bridge

This is my last photo of a bridge across the diminutive Heathcote River. The river's source (an underground spring) is about a mile west of this location.  After spending two months looking at two small meandering rivers, readers might think that New Zealand's South Island is a flat meadow. Actually, there are large braided rivers just north (the Waimakarira) and south (the Rakaia) of Christchurch. Also an enormous mountain range to the northwest and an extinct? volcano to the southeast. Very few highways and very few highway bridges though. We'll take a look at a bridge across the Waimakarira River tomorrow.
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New Zealand's Bridges: Smartlea Street Bridge across the Heathcote River in Christchurch by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Tuesday, August 9, 2011

New Zealand's Bridges: Malcolm Avenue Bridge across the Heathcote River in Christchurch

March 2011 (-43.565 Degrees, 172.639 Degrees) Malcolm Avenue Bridge 
A steel girder bridge that more closely resembles a Vierendeel deck truss. It was built in 1960 and suffered only minor damage during the February earthquake.
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New Zealand's Bridges: Malcolm Avenue Bridge acres the Heathcote River in Christchurch by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Monday, August 8, 2011

New Zealand's Bridges: Sloan Avenue (Gillespie) Footbridge across the Heathcote River in Christchurch

March 2011 (-43.569 Degrees, 172.639 Degrees) Sloan Avenue Bridge

Another damaged footbridge across the Heathcote River. My hosts from the University of Canterbury, Simone and Alessandro are standing on the bridge. 

I like the big round piers on each side of the river. They support a prestressed concrete T girder main span and side spans that descend to the ground. During the earthquake, the two piers moved closer together which cracked open the  top of the main span at the ends (see figure below). 

They put up tape to stop people from using the bridge, which apparently wasn't a very effective disincentive for people needing to cross the river.
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New Zealand's Bridges: Sloan Avenue (Gillespie) Footbridge across the Heathcote River in Christchurch by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.