Largest steel span?

[MIKE_311]

Does anyone know what the longest steel girder span or floor beam/stringer span system is in the US? Depth of girder would be a plus.

Looking to do some loooong spans with steel instead of segmental concrete or truss.

I'm looking for structural practicality, the bridge has access to a major waterway so delivery of long pieces is possible

 

[BridgeSmith]

With barge access, getting long pieces to the site is not an issue, but the length capacity of the fabrication shops could be a limitation on the piece length. The shops that fabricate girders for us can only do about 125' pieces. The capacity of the cranes you can get to the site may be another limitation. Typical plate widths are limited to 12', so if they can't the depth of the web out of a single plate, you'll have a longitudinal weld in the web, which adds significant cost.

I know Missouri has done some massive steel girders.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[davidbeach]

If the fab shop doesn’t have barge access, they won’t be able to deliver oversized components by barge.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[MIKE_311]

Thanks for this, I figured figured fabrication would be a limiting factor. I didn't consider the web depth, however.

 

[bridgebuster]

I knew I had this ancient history somewhere. It's a Bethlehem Steel advertisement that appeared in a December 1959 edition of the NY Times. At the time, the longest plate girder spans in the US.

FWIW, I was resident engineer for the rehabilitation of the Q-Bridge, 30+ years ago. I have the rehab plans somewhere & I can see what the girder depths were. The original Q-Bridge was replaced a few years ago with one of the first extradossed girder bridges in the country.

 

[BridgeSmith]

Best to talk to someone at the fab shops in the area that do bridge girders, and find out what their limitations are.

Also, talk to a couple of the contractors who might have to erect such a span. We had a 285' span that went up recently, clearspanning a river with no skew. The erection for that was a little pricier than what's normal for us. The next crossing of that river was also supposed to clearspan, but at a 45 degree angle, the center span would have been 325'. It would have been about $5 million extra - we put a pier back in the middle of the river, like the old bridge had. The greater height (60' above the river vs. 15' for the first crossing) was probably a factor, but I'm guessing access to the site for a large crane and the weight of the pieces (50 tons) had alot to do with the extra cost. A couple of contractors (including the one doing the first crossing) said flat out they wouldn't bid the job.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[cooperDBM]

Would cable-stayed be an option for you?

 

[Guest090822]

I've designed I-sections to around 300 feet. It was a hybrid design. The web was around 10 feet deep if memory serves me correctly. Be careful with higher yield strength steels. I had to remind more than one good bridge engineer that the modulus of elasticity is the same for grades - deflections eventually become an issue.

 

[BridgeSmith]

Be careful with higher yield strength steels.

Yeah, the hybrid reduction factor applies, including in the bolted field splice design.

I had to remind more than one good bridge engineer that the modulus of elasticity is the same for grades - deflections eventually become an issue.

Ah, yeah, higher yield strength doesn't mean stiffer; it just deforms more before it reaches the yield point.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[Guest090822]

For composite design, people tend to want to use lightweight concrete too in an effort to reduce dead load. The modular ratio changes with lightweight concrete and you end up not getting anywhere. Isn’t bridge design fun?

 

[BridgeSmith]

Isn’t bridge design fun?

I love it! That 485' plate girder (100' - 285' - 100'), with staged construction and counterweighted ends spans, in high seismic zone, I did a couple years ago was definitely a highlight.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[bridgebuster]

Rod - is that the bridge you mentioned a few posts back?

 

[BridgeSmith]

Rod - is that the bridge you mentioned a few posts back?

That's the one.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[OSUCivlEng]

My coworker designed a 100'-275'-100' continuous plate girder a while back. Essentially used the integral abutments as counterweights.

Anchored end spans are pretty cool. Looks like a single span, but it's actually three.

He designed one of those back in the early 2000s as well. Very aesthetically pleasing.

 

[BridgeSmith]

My coworker designed a 100'-275'-100' continuous plate girder a while back. Essentially used the integral abutments as counterweights.

We weren't able to do fully integral abutments on the big one I mentioned, so we had to do semi-integral. The end diaphragm provided most of the counterweight needed, but we had to add concrete between some of the girders, as well.

We've done fully integral with H-piles embedded in drilled shafts for the foundation to get adequate uplift resistance from soil friction. The only problem we had with those is that the contractor 'forgot' to cast in the anchor bolts to hold the girders down during construction, drilled and epoxied the anchor bolts in, didn't clean the holes properly, and the ends of the girder popped up. Now we specify u-bolts to be cast in, so they can't do that again.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[MIKE_311]

I did find out the that the new Nice Bridge in Maryland has 350' spans with steel haunched girders that are 12' deep at the piers.

 

[BridgeSmith]

If you can get the girder pieces and a big enough crane(s) to the site, you can go pretty big. At a certain point, other superstructure types become more economical, though. The exact breakpoint will depend mostly on what the foundation materials are like.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[jorton]

I worked on one that was curved with skewed intermediate bents. Due to the bent skew, the outermost girder has a interior span of 390' with much shorter end spans. Girders were 10' deep. Thickest flange sections were 4"x42". The large span to depth ratio led to very large dead load deflections (feet rather than inches). Differential girder deflections led to cross frame fit-up issues. Pretty much everything was not ideal. I'd recommend respecting established span to depth ratios. Constructability and hauling constraints would them limit piece size which would then control span.

 

[bridgebuster]

The original Q-Bridge had 12' deep webs at the pier for the 387' span; 8 ' at the center.