steel beams encased in concrete

[jie5]

I am analyzing a structure that at first appeared to be concrete beams,girders, & columns. As we proceeded we discovered that there are steel beams encased in the concrete. The exposed steel on the bottom of the beam is 4" wide approx. 1/4" thick. The exposed steel in the girders is 4" wide, 1/4" thick and there are 2 of them 2" apart. Our end goal is to provide a load rating for the floors. We tried GPR to help determine some beam properties but was unsuccessful. The floor is 6" concrete w/ 6x6 wwf.

Anyone familiar with this floor framing system?

I have attached some pictures to better illustrate what we are looking at.
Picture 1 - Overall framing

Picture 2 - exposed steel in beam & girder

 

[TLHS]

I'm confused about the arrangement of the steel, and I can't tell from the photos.

Is the steel oriented such that it's carrying tension in a mass of concrete, or is it possible that they're just concrete fireproofed steel shapes? The latter isn't that unusual in older industrial installations.

 

[Ingenuity]

It has similarities to the Watson Reinforced Concrete Floor System, but that was precast not cast-in-place, so not sure if your project is a proprietary system.

I briefly checked the Antiquated Structural Systems Series articles in Structure Magazine by Stuart and came up blank.

When you GPR scanned the beams, did you scan the webs faces in a horizontal direction to detect any shear reinforcement outside the structural steel section?

This from Stuart's Antiquated Structural Systems Series Dictionary: Link

 

[jie5]

At first I was thinking it was concrete fireproofing. I guess what is really throwing me off is the width and thickness of the steel. At only 4" wide I did not find a shape that would be adequate to span 30' (beam span is 30', girder span is 21') I also checked old Bethlehem Steel manuals.

We did scan the webs in a horizontal direction and found shear reinforcement. The shear reinforcement was also visible at some locations due to poor consolidation of the concrete around the steel.

 

[SlideRuleEra]

jie5 - Your finding have me stumped. Do you have a date for the building's construction? Also, what is the estimated depth of the beams? Could the members be channels instead of beams? Can you tell if they are rolled sections or possibly stamped steel (steel lumber)?

At this point, I believe your best option is to email Matthew Stuart. Some time back I contacted him. Received a prompt reply. His email address is in the document that Ingenuity linked to, that email address should still be current. He probably would be interested in hearing from you on this subject.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[TehMightyEngineer]

Looking at the picture it really looks like there is a seam running down the middle of the flange. I've seen this before and would bet that SlideRule has it right; those are probably back to back channels or possibly a built-up beam from riveted angles and steel plate.

Maine Professional and Structural Engineer.

http://www.fepc.us