ACI 318 12.2.3 vs CRSI Tables

[HeavyCivil]

In double checking the development lengths and class a lap-splice lengths for a particular project I calculated the lengths out for each condition encountered on that job and tabulated the results (IE enter table with bar size, coating, conc strength and cover and scroll across to Ld).

In checking out CRSI tabulated lengths upon the suggestion of a superior I have noted that CRSI's Lds differ from values obtained using ACI 318 12.2.3 .

CRSI shows larger lengths for smaller bars but does show some reduced lengths for larger bars.

Can anyone shed light on this?

 

[dgkhan]

For anything when I designed and comapred with CRSI, data of CRSI seemed over kill. But if it's dev length is coming less for larger bars, it is news and concern for me too.

 

[HeavyCivil]

Has anyone else notice this? If you have a minute and are curious to see how much CRSI tables differ from eq 12.2.3 plug and chug your way through the calc a few times, and see if you discover what I have: that CRSI is conservative on smaller bar and... (liberal?) on larger diameter bar.

This is a CRSI table for "Tension development and Lap Splice Lengths for Bars in Walls and Slabs (ACI 12.2.3)" Published in "Reinforcing Bars: Anchorage and Splices" 2008.

So the table is based on that same calc. I have to assume I'm making the mistake- not CRSI- but if I am I can't see where.

There are variables not addressed by CRSI (like whether to take coating factor as 1.5 or 1.3 which depends on Cb=3*Db) but even if I stay conservative I find CRSI having lower numbers once I get into larger bar

 

[HeavyCivil]

For instance: A sample run through a column of their tables with my spreadsheet produces this (see attached)..

Hopefully someone points out an error I have made because I'd be much happier with my own inconsistency than inconsistency between two Institutes on which I rely heavily for technical support.

 

[HeavyCivil]

Easy does it...


A MEP guy in my office took a look at the spread sheet and added a bunch of if statements to make it account for code maximums which got my numbers darn close to CRSI.

So rest assured - by our analysis the tables are legit.