Enercalc Masonry Slenderwall Deflection 1

[MillR]

I'm designing masonry slender walls using Enercalc and I always have concerns with what it's doing.
The default load combinations for either IBC or ASCE for deflection include W only at 1.0. Which, as far as I can tell, is ultimate wind. Wall deflection should be at allowable levels, if I was doing it by hand. Florida building code allows deflection to be checked at 0.42W component and cladding, but even at 0.6W the design stops being so dramatically deflection controlled.

So two questions: 1) Is the 1.0W ultimate and why is this the default for deflection and 2) what are these code references in Enercalc? What does 25 mean?

 

[Aesur]

Assuming you are using a building code that references ASCE7-10 and later, the wind would be ultimate state. One of the first things I tend to do in EnerCalc when designing with wind is modify the deflection combinations as you mentioned. Use 0.6 if using MWFRS or 0.7(0.6)=.42 for C&C loading. Under Database at the top you can modify the load combinations to default to this if you wish. I should probably go ahead and do that. While I'm not sure why the default Wind deflection combination hasn't been changed to 0.6 or 0.42, I would suspect it's because the user can update so they provide a basis level matching the other load cases as deflection of wind depends on if you are using MWFRS or C&C.

 

[MillR]

Thanks Aesur. Every time I use Enercalc I start overthinking things like this.

 

[jerseyshore]

I think Enercalc has all the combos on by default, you just double click where it says "Yes" to turn it off.

The Code Ref is just the how the combos are numbered in whatever code book you picked.

 

[CConrad]

I can confirm that we provide the individual load cases (the ones with the word "Only") in the load combinations list as a convenience. If you click the Load Comb Control button above the Run column, there are quick options to select/deselect combos in groups.

It's also easy to start with our provided load combination sets, copy the one you use the most, rename it, and make edits to the load factors to suit your projects. Then you can use your custom load combination set on your projects without having to do repetitive editing in each calculation.

The Code Ref column was an attempt to make a direct reference to the numbers used in IBC or ASCE load combination lists. That falls apart when you get to the individual load cases. It looks like the number 25 refers to some internal list number that the program is using.

Director of Engineering
ENERCALC, LLC
Web:

http://www.enercalc.com

 

[MillR]

Enercalc person: You should reconsider having the default be adding a nonsense load case. I've looked back at all the masonry walls done by the younger engineers in my office and every one of them has conservatively had wind control deflection at ultimate load levels.

 

[Aesur]

Enercalc person: You should reconsider having the default be adding a nonsense load case. I've looked back at all the masonry walls done by the younger engineers in my office and every one of them has conservatively had wind control deflection at ultimate load levels.

At least your building is conservative! I do understand your surprise/frustration here; I have seen it many times by younger engineers as well. Keep in mind, this LC happens throughout the program, ie wood lintels designed as flat for out of plane, jamb columns etc.. so you may have other items that are conservative as well. Honestly though, I like the ability to change it myself and it's always one of the first things I look at when I check an engineers work and something looks odd with the design. It's also a unique learning experience for wind and deflection control and something that many engineers will not soon forget.

Edit: wanted to add: it's hard to default the program to 0.42 or 0.6 because depending on what you are designing, you may be using C&C or MWFRS, so it's best to be user controlled IMO.

 

[jerseyshore]

Wait, we're blaming Enercalc for providing too many options? It takes 1 minute to go thru a module and set the defaults for future calcs. If I were you I wouldn't be too worried about your conservative deflection designs. I'd be more worried that your engineers can't click thru all 4 tabs on a module. Let's hope they didn't miss anything else...

 

[MillR]

Clearly the engineer should be in control of the load cases. My point is that even though I know deflection should be ASD, the appearance of a load case I don't understand in a computer program that I assume knows what it's doing, referenced as "25", had me asking the question in the first place. I just think it shouldn't default to something that doesn't actually exist. If you don't hunt down what is driving the design, you would miss it.

 

[CConrad]

@MillR: Thanks for the comments. You'd be amazed at the spectrum of comments that come in on these subjects. Let it suffice to say that we would never be able to set up the software in a way that would satisfy the needs of every user with no modification. So we have done what we can to set up the system in a way that hopefully provides a little more than you will probably need (under the assumption that it's always easier to delete or modify something you CAN see, rather than recognizing and adding something you CAN'T see).

Aesur hits on the high points of why it's essential for the user to make the modifications that apply to a given calc. To carry that one step further, take a look at the footnotes to IBC Table 1604.3 and imagine trying to program that.

If you need any help with customizing your own load combination sets, feel free to drop us a line through normal support channels.

Parting thought...this has been a great discussion that will make your younger engineers BETTER younger engineers.

Director of Engineering
ENERCALC, LLC
Web:

http://www.enercalc.com

 

[MillR]

Indeed, CConrad.