Load factors in ACI 318 1971 1

[dcceecy]

we are checking a concrete floor built in 1974.
The current load combination is 1.2DL+1.6LL from ACI 318.
I am wondering what they used in 1974. 1.4DL+1.7LL?
we do no have a copy for ACI318 1971. Can anyone help me out?
Thanks.

 

[BAretired]

I have ACI 318-63 but I don't know if that would have still been in effect in 1974. It specified:

U = 1.5D + 1.8L
or
U = 1.25(D + L + W)
or
U = 0.9D + 1.1W

BA

 

[BAretired]

I believe you can purchase ACI 318-71 online for $25.

BA

 

[hokie66]

Be aware that some of the capacity reduction factors may have changed as well.

 

[woodman88]

Or you can pay $163.50 (

http://www.cement.org/buildings/resources.asp?cat2ID=2)

and get all from 1908 tom 1999.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[JedClampett]

If you can wait until Wednesday, I have ACI 318-71 in my office. But I'm on vacation now.

 

[dcceecy]

JedClampett
Thank you. Please let us know the load factors and the reduction factor of ACI 318 1971

 

[dcceecy]

I did some research online and found a paper talking about the load reduction factors of earlier days.
Please see the attached pdf.
According to the paper (to calculate the overall or global factor of safety, line 12-18), we can solve these two equations to find the load factors
a*D+b*D (=L) = 1.72*0.9*2*D
a*D+b*D/2 (=L) = 1.67*0.9*1.5*D

then a=1.4, b=1.7

Somebody please verify those load factors if you have ACI318 1971. Thanks.

 

[PT999]

ACI 318-71
U = 1.4D + 1.7L

 

[msquared48]

YUP. That's what mine says too. Absolutely amazing!

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[dcceecy]

Thank you for the verification.
I am very curious now. why are those load factors used in cocnrete (in such earlier days) while ASD were used for almost all other materails?
Does that come from a tradition or the ACI 318 committee just adopted some research paper using load factors? Does anybody know the particular reason?
Sorry, too many questions.

Thanks.

 

[JedClampett]

My guess is that the failure mechanisms of concrete used with LRFD were:
1) Easier to calculate
2) Easier to match with test data
3) Someone had to be first.