steel beams from 1906

[ick2]

i am checking some steel beams from 1906 in New York City. Based on AISC at that time, the allowable bending stress was around 16 to 18 ksi. However i have tested the material and found that the yield stress is 38300psi and the tensile strength is 64300psi. The percent elongation in 2" is 26.5%. According to today's AISC code the allowable bending stress is around 24ksi. Csn you think of any reason why not to use the higher allowable stress?
thanks

 

[unclesyd]

Based on what I've seen on some old beams they were not very uniform in cross section. There was considerable difference end to end and beam to beams. The difference in relation to each other was attributed to the ends, too much, of the billet being used. Also the steels and irons of the day were extremely dirty, especially the Silicon and Sulphur, which would affect the transition temperature. Have you pulled any of the rivets for examination. these impurities were very detrimental to the steel and would affect the irons if welding (thermite)was attempted.

Have you checked to see if there is any wrought iron mixed in among the steel, brackets and braces.

Just for curosity who made the Steel for the beams?

 

[ick2]

i have no idea who made the beams. i had a coupon taken from the end flange and we tested that. from the size of the beams some said that they are 15" american standard. the testing lab told me that this steel is weldable (if that tells us anything). Some other info on the composition is given below:
carbon 0.2
manganese 0.97
phosphorus 0.044
sulphur 0.03
silicon < .01
chromium <.01
nickel 0.03

 

[NickE]

From looking at a large # of chemistries for low alloy and low carbon /IF grades of steel sheet, this looks relatively clean. The phos is a bit over modern specs and will definately cause an increase in the transition temp esp. at high velocity applications of force.

I would be worried about overall consistancy of the beams end to end and beam to beam however.

nick

 

[stanweld]

Your steel is very likely semikilled and is typical of A-36. As NickE stated the high P & S,typical of the time, promote a relatively high ductile to brittle temp. expected to be > 32 F and more than likely > 50 F. You may well have lamination in some of your beams depending on ingot to final product yield. Ladle reactions (oxidation of carbon and manganese) were common during pouring of these steels and some of the steel may have been subject to same and could easily lead to the non-uniformity of steel stated by unclesyd.

 

[stanweld]

Oops, I erred. This is a rimmed steel - and the toughness properties are even worse. Also the potential for a ladle reaction during pouring is also greater.

 

[MetalMickey]

Agree with Stanweld, it is a rimming steel. My concerns would be poor toughness of the material to unexpected loading regimes, and the variation in cross section. Since I guess these have been in action since 1906 so are likely to have had varied loads applied. Given the possibility of stress concentrations as a result of section irregularities and possibly almost 100 years of fatigue loading, I would be inclined to be cautious.

 

[stanweld]

I too would advise caution. Other Codes, most notably the NBIC, do not permit the use of the current higher design stress on pressurized equipment manufactured prior to the 1968 Edition. Should failure occur and the building collapse or partially collapse due to use of the current design stresses, the liability costs could be staggering. From a financial risk standpoint alone, I advise not deviating from the original design conditions.

 

[unclesyd]

If I remember correctly from work we done in the fifties with some steel of about the same venue, except from Birmingham, Alabama. The discussion was mostly about what steel used in building construction being used essentially all in compression. There was very little diagonal bracing in the older buildings I saw being demolished due to being mostly of masonry construction and apparently very little consideration was given other loadings on the steel columns. A lot more attention was given to the rivets than the beams. Looking at one of my father’s International Correspondents School books, circa 1924, there is little consideration given to moments on columns, a lot on rivets in shear and the connections in vertical columns, with a little discussion on diagonal bracing.
Again based on my recollection of these events in my younger days I wouldn’t push the envelope even though the design of times probably would have been quite conservitive by today’s standards, simply by the methods of calculations used.

P.S.
The tensile testing machines of the time weren't very good as a lot depended on the operator keeping the beam balanced. There was a propensity to throw out very bad values if the fracture surface had discernible imperfections.