Bridge with no bearings! 1

[Roadbridge]

One of the structures on the contract I’m working on is to be constructed with no bearings. This is the first time I’ve encountered such a structure and was wondering is this normal practice?
The bridge consist of a 50m span deck sitting on an arch profile all cast in-situ and monolithically fix to the abutments.
The abutment themselves are 10m high from soffit to finish road level.

 

[SlideRuleEra]

This is done from time to time. As a bridge contractor in 1977, we constructed a 116 ft. long, three span, highway bridge over a railroad. Each end span is 36 ft. long, the interior span (over the RR track) is 44 ft. The entire deck (all 116 ft.) is monolithic, cast in place concrete. This deck is fixed to all four bents with rebar dowels .

The reason, in this case, was the RR company's concern that a bridge with simple spans could more easily collapse during a train wreck under the bridge. As is typical on bridges over railway lines, both interior bents have substantial concrete collision walls that parallel the tracks.

This seemed unusual to me, too. So I saved the plans - on this occasion don't have to talk from memory, am looking at the plans right now.

http://www.SlideRuleEra.net

 

[Qshake]

Yes, this is fairly typical nowadays and based on what SlideruleEra has noted it's been out there for some time too.

Tenessee is one of the leading DOT's on jointless bridges consequently for smaller structures, they are also bearingless.

MOst other DOT's are following suite and bearings can be expensive.

Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

 

[LittleWheels]

Common practice in the UK nowadays.

 

[Roadbridge]

Then I most ask the question. Why were bearings used in the first place? What has caused such a shift in design?

 

[LittleWheels]

It was easier to calculate non-redundant structures (simply supported) rather than continuous. The maintenance wasn't seen as such a big problem as now.

 

[Qshake]

On that last subject, labor was cheap to the DOTs and other agencies. Maintenance could actually be performed at a reasonable cost...today everything is about lower labor cost and or maintenance costs, if not both.

Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

 

[flamby]

Arch bridges have no bearings because they need to be "both-ends-fixed" in order to develop arch action.

Ciao.

 

[HgTX]

By making a jointless bridge, you take all your joint trouble and convert it into abutment trouble instead. It all depends where you find your trouble easiest to deal with.

Hg

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