Curtain Wall Design 2

[kodstruct]

Hi there,

Lately I have been getting calls from contractors to design curtain walls and storefront systems for them So I am thinking to start my practice in the area.
Is there a good software out there for this?

Thanks.

 

[RFreund]

Digging deeper...

I'm still trying to get a feel for what is industry standard...
I've contacted the manufacturer used for this project (a well known manufacture may have even been mentioned previously) and so far the information I'm trying to get seems to be difficult to get a hold of. Part of the problem seems to be that the shapes are proprietary so they don't want to give you the full geometry of the section. When asking for the section properties, they can give you S and I and c (section modulus, moment of inertia and distance from N/A to extreme fiber) for the shapes but they don't provide (atleast not commonly) J and C.w values. I also politely asked about talking with thier engineer and was told that is basically impossible (not saying that the people I was speaking with weren't very helpful, they were).
It seems as though if you use the 2005 (allowable stress method) of Aluminum Design Manual (ADM) you only need J. From talking with the manufacture they seem to calculate J for tube and Channel section just using basic approximate formulas ignoring the 'kinks' in the shape and using an average thickness. I kinda feel like I'm trying to uncover some secret society.

So below is where things are at and I'm curious if anyone can say hey your overdoing it or you're on the right track.

1. Checking mullions: First check the tables provided by the manufacture. To me these are a bit misleading because they don't really determine where the horizontal mullions are applying point loads, however maybe they are conservative. So you could check your height and spacing and if you are withing the limits then you're good. You still however may need to check your horizontal mullion for lateral load as these may not be in the charts. So it seems c, I and S values are provided somewhat readily. So you can check deflection, but now what about strength. Well you you would need J and if using 2015 ADM you many need C.w. Now the question is what is the standard level of analysis used. I see a number of ways this could go - (1) The manufacture provides detailed geometry and we calculate the section properties. As noted previously I think they are hesitant to do this given the proprietary shape. (2) The manufacture gives you all the required values (check out ADM illustrated examples curtain wall and you will see there are many variables). Also my experience thus far has been like pulling teeth. (3) You estimate the the sectional properties neglecting the kinds/bends. This currently seems like it is done. (4) You are within the range of the charts and it is likely strength (at least LTB) is not a concern. Check other limit states (i.e. local buckling, section strength). Maybe use this in combination with option (3).

2. Checking fasteners - I was told that the charts do not consider fastener strength. Therefore the screw/fastener properties need to be obtained from the MFG. Or the the allowable loads. This has actually been a somewhat difficult task as well however I believe I know have this information. It would be nice if they provided an allowable load as this again is a long calculation (Although I refer the reader to AAMA TIR A9 for info.

3. Anchoring to substrate - this seems to be the most straight forward as I get to select the anchor.

4. As Glass had mentioned think long and hard about your fee and willingness to get into curtain wall design. I haven't even started on some of the other considerations that other submittals that I reviewed seem to have overlooked or discluded.

Any comments are appreciated. Thanks!

EIT

http://www.HowToEngineer.com

 

[kodstruct]

@RFreund,

Thanks for the information.

I got a signed proposal this morning for my first project and I am in the same boat as you.
The specs from the Architect calls for Kawneer product.
I went to their webiste for information. However, I don't think they have all the shape they use to manufacture their curtain wall system. I am to use the 1600 SS system and they only have few members with I & S values in their wind load chart section.

@RFreund, do you have a technical catalog or CAD file of all their shapes? You are right about the approach you described in your previous, at least it makes sense to me.

The design process itself is straightforward if we have something to work with especially, the Architect (Specs) says NO substitution. So I have to use Kawneer.


I will call Kawneer to see if theyc an help.

Thanks.

 

[RFreund]

That will make 2 of us.
I have no such cad file but you can download their details online. These have the shapes but I'm not sure if they are drawn exactly to scale. Also try to find their estimating guide which relates sizes to part numbers.

If you some how get to their guarded engineers. Let me know what they have to say, I'd like to pose these questions to them and try to understand their tables. Also for their clearwall system they actually tape a component to the glass which attaches to a toggle.

EIT

http://www.HowToEngineer.com

 

[Ingenuity]

Maybe it is indeed a 'secret society', outside the USA too.

When I had to check a aluminium section from an Australian manufacturer (Capral) for a project I had to obtain a company issued login to their online site to get the info. Once logged in, I had access to a lot of data, including CAD drawings of sections etc.

Good luck.

 

[kodstruct]

Then it's serious.
if they manufacture something and want Architects to specify them then they should have catalogs where engineers will get the data just like Verco, Vulcraft, etc.....
At the end of the day, the products will be shipped from their warehouses, so i don't see the issue.

Is it like that? Seriously... How curtain wall engineers do? I have 3 weeks to complete the design & shop drawings.
Any help?

Thanks.

 

[glass99]

Generally speaking if you are doing standard Kawneer 1600 with no funny business, you don't need their CAD files. Lateral buckling is not really a thing with tubular sections. However if you feel you need it, CAD sections are available on their website.

http://www.kawneer.com/kawneer/north_america/en/cad_spec.asp?prod_id=1801&area=prod

 

[glass99]

kostruct: three whole weeks? Welcome to the glazer's schedule. When you work for an owner or arch your schedule is measured in years, when you work for a glazer its weeks. Its a pretty jarring difference. If you do the same thing in the middle east its measured in days. Spoke to an engineer in Dubai a couple of years back who designed a 100m span roof with complex geometry, custom milled steel nodes and a funky islamic pattern for the structural members in two weeks. It was insane.

 

[kodstruct]

@Glass,

Great info. thanks.....
Yes 3 weeks, lol...I thought I could access the manufacturer catalog when I wrote the proposal.
I clicked on the link you sent and they only have few types (162001, 162002, 1620090 vertical mullions). I hope these types work with the wind my design.

Thanks a bunch.

 

[RFreund]

Yeah we the have same time frame.

I found the cad files as well, however it seems odd that they would have a to scale cad file with exact dimensions but not distribute a dimensioned drawing. I did a Massprop in autocad and it appears to match the I values published in the wind load charts so maybe that is accurate.

So it seems like if you're layout is fairly typical there isn't too much to worry about and could perhaps use simplified geometric properties. But then that begs the question, what if it's not such a simple case.
It would be nice just to see a detailed strength design calc from the manufacture similar to in the ADM for the curtain wall example. Then you'd have all the values. I know this is a bit much and would take all the fun out of it. But I'm assuming they must have went through this procedure at some point.

EIT

http://www.HowToEngineer.com

 

[kodstruct]

RFreund,

That's right....I just did the massprop as well and it matches.
My curtain walls are 13' so i hope these sizes work. If it doesn't I will add aluminum C channel or something for reinforcement.

 

[RFreund]

Another question here...

Are sills typically designed to carry the dead load (and lateral load) of the glass between vertical mullions even if there is substrate below (Similar to intermediate horizontal mullions)? Usually there is gap between the bottom sill and the substrate but you could add blocking in which case you wouldn't need to span the sill between the vertical mullions. However unless the substrate is foundation the member is probably not designed to support glass vertically. So I suppose any situation other than the blocking between foundation and sill the sill would need to span between vertical mullions, no?

Is the only connection to the substrate then typically at the T&F anchors at the vertical mullions or is the sill (or head for that matter) ever fastened to the substrate as well? I would think not, as you would want to allow for differential movement and the only way this is accomplished with through the T&F anchors, right?

Thanks!

EIT

http://www.HowToEngineer.com

 

[Thinktanck]

kodstruct...

I'm new to this forum. I actually joined after I read this CW thread. I'm an Engineering Team Lead for a company that designs custom unitized curtain wall. Prior to this, I was Engineering Manager for a similar company that only used stick systems (Kawneer, Efco, Tubelite, etc...) I've also done contract work for glazing and ACM panel companies. You are correct in your assessment of the industry. It is a niche. A lot of our interns or new hires have degrees in Mechanical or Structural Engineering, but there is a lot of intense facade specific training that we give them. I'd like to know how you are doing in your "infiltration" into the CW world. lol. Maybe I can help.

Thanks