Rolled Steel Beams and HPS 70W Steel

[willijamie]

Is it possible to get W18, W14 rolled beam shapes in HPS 70W steel or are they available only in Grade 36W and Grade 50W steel. I am trying to minimize my section depth due to hydraulic concerns on a small bridge project. Any help would be greatly appreciated.

Thanks!

 

[HgTX]

HPS 70W only comes in plate. ASTM A 913 comes in a Grade 70 but it's not a standard bridge steel (despite the word "bridges" in the first paragraph of the spec); the Bridge Welding Code, for example, is written only with the various grades of ASTM A 709 in mind.

Hg

 

[TTK]

If hydraulic freeboard is a concern then weathering steel may not be the best solution, as it doesn't perform as well in continuously moist environments.

How long is the span? If less that say 110 ft., why not use prestressed butted box beams? This is the shallowest system going and performs very well in low clearance stream crossings.

 

[HgTX]

Under paint, weathering and nonweathering steel are much the same, but you gotta watch out for unprotected crevices. There's no nonweathering equivalent for HPS 70W.

Hg

 

[Qshake]

You've probably already checked this but it doesn't hurt to reiterate: Don't forget to check your deflections and specific requirements from what agency you're working for. Many times HPS won't work due to more strigent deflection requirements.

Regards,
Qshake

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

 

[willijamie]

Our State Project manager has requested the use of weathering steel based on information he has received from FHWA on the uses of weathering steel. We previously looked at concrete beams but the bridge varies in width 13' with a span length of only 42'. I was hoping HPS 70W was available in rolled shapes to reduce our section depth as much as possible. Thank you for all your replies and suggestions.

 

[HgTX]

How shallow does your section need to be?

I guess you could just close up your girder spacing to use smaller beams.

Then there are always those cute truss bridges.

Or widening the bridge at the narrow end to make it constant width--is that a possibility?

Hg

 

[ghghghgh]

It's been awhile since I've done a rolled beam superstructure, but 42' doesn't sound too particularly long of a span, the depth limitations must be severe. I seem to recall 70'-80' as a rule of thumb cutoff.
Is your framing plan splayed now?
If you can't tighten the girder spacing as HgTX suggests to add a beam, can you use short framing beams (our term) coming off the main beams at the wide end? In other words, make the main beams parallel to reduce the wide end spacing, and add maybe a 15' beam coming off at an angle on each exterior beam to pick up the turning radius or whatever is driving the flared-end requirement.

 

[fuchsjr]

You could also just vary the spacing at each abutment. Have one abutment at a tighter spacing than the opposite end. Splay the girders.

 

[willijamie]

We presented that option but the client doesn't want to proceed with that option. The client requires stay-in-place deck forms on all projects and would like to keep all beams with a constant spacing. Splaying the girders helps out greatly but it is not what the client wants.