Old metal joist type, need help identifying from photo, Cast Iron? 3

[PEVT]

Hello All,

See attached photos of metal joist/rafters, vintage is 1942 or earlier, they appear when you look very close to be cast iron. 24ft span, supporting roof. "T" shaped top and bottom chords with bar shaped web lacing. There are no welds visible at the intersections of the the web lacing. Adjacent larger steel beam and column framing is clearly stamped with Bethlehem Steel. The Bethlehem Steel catalog from that period doesn't have any open web members like this and the joist don't have any identifiable markings. Any idea what they may be?

 

[PEVT]

See Additional Photo

 

[JAE]

That looks like a Kalman Joist -
Here is a reference - look at Figure 24

http://www.structuremag.org/wp-cont...EngrNotebook-Antiquated9a-Stuart-June-091.pdf

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[jike]

The configuration of the members would put some in tension and therefore would exclude the use of cast iron. Cast iron is traditionally used only for compression members. I would guess these members to be mild steel.

I have seen these types of joists or trusses before and suspect they are from the 20's or 30's. I would guess that these were before the days of SJI standards and most likely was a proprioritary design.

Unless you can find some load tables or a documented capacity, you most likely will have to fully measure up all steel members, welds, etc. and do a complete structural analysis of the truss for its capacity.

 

[JAE]

See the attached - these are tables from the Carnegie Pocket Companion 1934 with two pages of joist tables. Not sure if yours is a Kalman or the other.

These come from SlideRuleEra's website found here where you can download the entire book:

http://www.slideruleera.net/structural-steel-handbooks.html

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[oldestguy]

If more is needed, sometimes identifying steel type is done by the spark test. An angle grinder would be the tool to grind a little where it is not critical. The pattern of the sparks tells a lot.

 

[MikeHalloran]

Wow, that Kalman truss is such a cool idea; just take a rolled I-beam, pierce the web, and stretch it out like a piece of expanded metal.

The original material just _has_ to be mild steel for that to happen without fracture.




Mike Halloran
Pembroke Pines, FL, USA

 

[hokie66]

Mike,
Yes, it was a hot rolling process.

 

[Ron]

Definitely not cast iron. Is mild steel.

 

[PEVT]

JAE - You hit it spot on with the identification of the member and helpful guidance to the reference resources I will need for determining member details and capacity. The KalmanTruss open web steel joist on page 387 of the Carnegie reference was an as-built match. You are all correct, definitely not cast, but wow do they look like it, with the seamless joints and chamfered edges. Thank you very much. A thank you to everyone else who weighed in, as you comments helped to inform my thought process. Great work, much appreciated.