1931 Building 2

[PEinVA]

I have a building built in 1931. It shows a one way rib slab supported by steel beams encased in the rib slab. I have some designations that cannot be found in AISC published data for historical beams. The numbers match some beams, but the exact designation is off, and I'm just trying to determine if it is something that be overlooked, or it means to designate a different beam.

I have a 27C145 and in the book I find a 27x14 or CB272 but the weight is 145.

18C57 shows up as 18x7 1/2 or CB181.

Would these be the same beams. Also, What would the steel strength have been at this point? Unfortunately it is not listed on the structural drawings we have.


(Also we have some of the SHOP drawings for this job!) I love that we can't find this information for buildings that are 3 years old, but have it for a building that is over 75 years old, and during a time where I'm sure shop drawings were not common.

Any help is appreciated.




RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke

 

[SlideRuleEra]

RC - IMHO it is reasonable to assume the the notes refer to beams with specific height & weight. There were several ways to designate beams during this time and the exact answer is not always obvious. For starters, suggest that you download "AISC Iron & Steel Beams, 1873 to 1952" from this page of my website:

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

The current AISC Design Guide 15 is based on this 1953 publication, but the 1953 book gives more detailed info.

For your 27C145, see page 45. There are three different entries for 27" beams that weigh 145 lb/ft. If you follow the tedious footnotes, only one of these was available in 1931 and it was made by Carnegie.

For the 18C57, see page 60. There are two different entries for 18" beams that weigh 57 lb/ft. Again, following the footnotes, in 1931 one entry was from Bethlehem the other from Carnegie.

This is where the educated guessing comes in. The letter "C" was the accepted abbreviation for Carnegie in 1931 (see page 4). I would interpret the "C" in the notes in your examples to mean that the beams specified were made by Carnegie.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[PEinVA]

SlideRuleEra,
Thanks for the information. I already have the publication and found everything you had said. I figured this was the way they did it, but I just had to have someone confirm.

It seems you might even have been designing then!



RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke

 

[SlideRuleEra]

RC - I'm not THAT old , but both my father and uncle (from whom I learned much about the "old" ways) were practicing in 1931.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[jike]

It think in 1931 they were using ASTM A7, 33 ksi. Sometime in the 20's (1924?), they switched from A6 (30 ksi) to A7 (33 ksi).

 

[racookpe1978]

I'm looking at the AISC "Historic" listing using AISC's David Homes Steel Shapes interactive lookup program.

Characteristics for the CB272N and 18C57 are on the screen captures.

 

[racookpe1978]

And for the other one:

I like this lookup program because it has the older shapes, and because it's search functions for the newer (nowdays) shapes are straightforward.

 

[hokie66]

RC,

Glad you have found the information you need. But I was interested in your comment about shop drawings not being common in 1931. I would have thought the opposite, but agree that it is not common to be able to find them.

 

[PEinVA]

hokie,
I was just thinking that the structural engineer called out specific sizes that were unique to a mill and that was used. Maybe I'm wrong.

Anyways, another question, I have a one way rib slab with clay tile forms. The concrete mix is given as 1-2-4 mix.

2 Questions:

1. What does that concrete mix typically get me? Where can I look for information on this?

2. What should I assume for DL of the clay tiles?

Thanks!

RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke

 

[InDepth]

Anyone think about coupon tests to determine the steel yiels strength and weldability? The interwar years had steel that was improved from WW1 but wasn't yet up to the best quality until after WW2.

RCraine, what are you doing to this building? Is this an adaptive reuse, modification, or analysis?

 

[PEinVA]

Analysis for some storage filing. Currently there are library stacks on most of the flooring, but they want to move flat files in also.

We didn't do any analysis for the library stacks, but the floor was only originally designed for 70 #/ft2.



RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke

 

[racookpe1978]

1. To properly add the second image:

2. Careful: Library-type stacks (racks of paperwork!) tend to create extremely heavy floor loads with narrow aisles

 

[PEinVA]

I understand. Unfortunately they are removing the stacks and replacing them with flat files. The weight for the flat files is ~210 #/ft2, with a 4 foot between walk way.



RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke

 

[PEinVA]

Follow up question:

The drawings, of course, don't indicate reinforcing steel yield strength. I have found documents from around that time that indicate there were 3 strengths used: 33ksi, 40ksi and 50ksi.

Was one more prevalent than another?

RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke

 

[PEinVA]

Also, I found some information that rebar had not been standardized for area of bars etc. I found some variation in the range of 15% for area.

I am planning on using todays sizes, as they were the worst case of the 3-4 different sizes I found, but was curious for future projects as well.

TIA.

RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke

 

[SlideRuleEra]

RC - See the attached papers on older concrete reinforcement. There are a total of six pages, the first four are from the Concrete Reinforcing Steel Institute (CRSI); the last two are from the Portland Cement Association (PCA).

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net