Historic I-beams are not on any chart; need weight ratings

[johnkgeorge]

My client has an old (100 yrs+/-) one lane vehicular bridge over a canal adjacent to a railroad. The bridge was probably built by the railroad. I am being hired to replace the 4x12 creosoted timber deck with a composite steel/concrete deck. The client is concerned that the concrete will materially reduce the load capacity of the bridge. The problem in calculating the superstructure capacity is that I cannot find any info on the I-beams that are in place. They are 10.5" wide, 15" deep and have a flange thickness of .5". There are six beams in each span, and the span is 23', and rests on round timber piles and a 12x12 timber beam. I just need some basic load ratings for the steel so that I can show how the increase in deck weight relates to the theoretical capacity of the existing i-beams.Thanks

 

[JAE]

Don't forget to test the steel for actual Fy yield stress.

Get AISC's Design Guide 15 which has all the historical steel shapes back to 1887.

http://www.aisc.org/Template.cfm?Se...=/Ecommerce/ProductDisplay.cfm&ProductID=1138

 

[MiketheEngineer]

With that much info - you could derive the Sxx or Ixx.

Watch your yield values as noted. They use to be low or all over the place.

Why not consdider keeping it "historical" and replace timbers with timbers - just different treatments.

 

[SlideRuleEra]

For detailed information on steel members and steel design parameters from that time period see
"Wrought Iron & Steel In Construction, Pencoyd Iron Works 1892"
on this page of my website

http://www.slideruleera.net/contributions.html

and
"Carnegie Pocket Companion - 1923"
here

http://www.slideruleera.net/miscellaneous.html

http://www.SlideRuleEra.net

 

[msquared48]

Is this a constant thickness flange or variable thickness? If it is variable, there is a beam at the bottom of the G15 list on page 64 of AISC's "Iron and Steel Beams 1873 to 1952" that comes close to your dimensions.

A hundred years ago, for wrought iron beams, the allowabls stresses were in the range of 10 to 14,000 psi. For Steel, 12 to 16000 psi.

Better make sure of your material as well as the dimensions lest you have to be conservative with your design at 10,000 psi for the steel or iron members.

Mike McCann
MMC Engineering