The viability of light-gage steel construction. 3

[rlflower]

I am a licensed Civil Engineer who recently obtained accreditation as a LEED Green Associate. I have stong interest in encoraging expansion of the light-gage steel construction market.

My motive is simply to ecourage what I see as the most viable method of construction in California. Farmed lumber used in wood construction I believe is not capable of keeping up with the demand, and produces a product of cheap quality not becoming of a construction industry. Farmed lumber is not environmentally sound.

Do you have comments on this line of thought?

 

[csd72]

There are plenty of resources on sustainability for construction in the uk. They are way ahead of you here.

I suggest you try and google some.

Steel really depends on the recycled content. You may find that the recycled content of light gauge material is low due to the high yield strength required. As usual these things are more complicated than they first appear.

 

[slomobile]

csd72 is right, more complicated than they first seem.

There are lots of issues here, one is: Availability of workforce.

 

[rlflower]

To support our discussion, see attached file containing abstracts from a symposium of light gage steel construction, held in Hong Kong in 2004.

Thank you for your contributions. I will continue to contribute with supporting information and responses to your comments in the near furture.

Richard L. Flower, P. E., LEED Green Associate

 

[rlflower]

This is a very good essay on the subject.

Richard L. Flower, P. E., LEED Green Associate

 

[MiketheEngineer]

There are a number of resources - just google. You will get the vendors and their opinions. There is also a structural engineering association devoted to this --- something Light gauge SE association LGSEA or near that??

 

[rustyjames]

http://cfsei.org/

 

[drawoh]

rlflower,

Steel is not a renewable resource, either. You can always plant more trees.

Steel for cars gets recycled, and you can make more cars out of it. I do not think houses are quite as neat as this.

JHG

 

[rlflower]

Steel is the most highly recycled material in the world, with a minimum recycled content of 25%. In 2009, the Steel Recycling Institute announced that the current recycling rate for steel has reached a record high of 83.3%. Steel is considered a pre- and post-consumer recycled material and is therefore considered a sustainable material. Given that steel is North America’s most recycled material, this material contributes toward Recycled Content points under LEED, and diverting the project’s waste from landfill contributes toward Construction Waste Management points under LEED. Steel mills are distributed throughout the United States allowing the steel obtained from them to frequently satisfy the requirement for raw materials to be harvested within 500 miles from the project site, thus contributing toward Regional Materials points under LEED.

Richard L. Flower, P. E., LEED Green Associate

 

[dcarr82775]

Residential Framers like wood. Getting them to switch will be harder then anything else.

If somebody would come up with design equations that did not require help from Einstein to understand I would also be more agreeable to using cold formed steel. I am not a fan of using the black box tables the manufacturer's provide.

 

[rlflower]

I understand dcarr82775's concern. However, leave it to the manufacturer to support their products with the technical information you need. They realize they cannot sell their products without providing such information. Manufacturers associations such as the Steel Stud Manufacturer Association (SSMA) take all the headache out of the work by supplying tables with all the properties of the section profiles for which all their members comply to. Or, you can go directly to each manufacturer and request properites of their products' profiles.

Richard L. Flower, P. E., LEED Green Associate

 

[msquared48]

Steel stud framing works good in more humid climates, subject to insect infestation, such as Hawaii and the southern states.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[wannabeSE]

rlflower,
I stoped using the SSMA Product Technical Information. SSMA's published moment capacity do not always agree with the AISI manual. In some cases, the SSMA lists a 10-15% higher moment capacity. It seems as though the SSMA uses a different method for determining the strength increase due to cold forming. Someday, I will go through the calcs to determine the strength increase. It would be nice to find a (good) text book for cold-formed steel.

 

[csd72]

wannabeEIT,

I expect that you will find the SSMA is based on testing rather than purely on code. I could be wrong though.

 

[abusementpark]

I think light gage steel framing is ultimately a better product than wood framing.

However, I agree that there are problems with the complexity of the code. Most of the light gage steel design on our jobs is delegated and provided by the light gage steel supplier. We have had some trouble with getting decent submittals, but I think contractors are beginning to understand that detailed calculations are required.

When we do our own light gage steel design, we always use some sort of black box program for design, since the code can be rather complex when buckling modes are applicable. Now, I have seen consistent results from program to program (anyone use the Clark-Western program?). I think it would be helpful for the industry to offer some free webinars/seminars that give an overview to engineers on the benefits and capabilities of the system, as well as an overview of the code equations and applicable limit states. We have used light gage steel successfully to please a client in high wind situations.

 

[dcarr82775]

rlflower,

In the past I have used Expansion bolt tables that came with ICC reports. That is the exception.

I tend to not use load tables produced by manufacturers for their own products for a rather obvious reason. At least half the time I can not match their values and for some reason their values are always stronger in these instances. Now if they are willing to eat the design liability that is another story.

 

[rlflower]

Perhaps SSMA provides data based upon testing, or perhaps the data differs from other sources because the studs are (or are not) punched. Would it not be appropriate to ask SSMA directly how they come up with their structural properties? Their catalog suggests the tables are in compliance with Procedure 1 of the AISI specification.

I concur with abusementpark that the industry should offer "some free webinars/seminars that give an overview to engineers on the benefits and capabilities of the system, as well as an overview of the code equations and applicable limit states". Perhaps the Steel Framing Alliance is the door to knock on?

Richard L. Flower, P. E., LEED Green Associate

 

[rlflower]

Here is a link to the Cold-Formed Steel Engineers Institute (CFSEI) web page describing seminars that they offer to engineers.

Richard L. Flower, P. E., LEED Green Associate

 

[rlflower]

This link describes validaton of SSMAs structural cold-formed steel framing cerification.

Richard L. Flower, P. E., LEED Green Associate

 

[rlflower]

Offered for discussion:

With the history of construction in California in mind, we have seen light-gage metal framing coming of age in the last 40 years. Why is light-gage metal framing considered a viable option? Drawing from the experience gained from major structural steel framing and from wood construction, the structural engineering community is finding ways to answer the need for a cost-viable option using light-gage metal framing, while eliminating the need for major structural steel lateral-load-resisting systems. This results in a light-weight structure that is also light on the pocketbook. Numerous manufacturers have a long history of producing light-gage metal floor joists, wall studs, and shear wall systems. The cost of light gage metal framing has held steady over the years when compared to the wild cost variations of wood framed construction; for residential construction, the cost of labor may be more, but the material cost is much less, resulting in (roughly) one or two percent more in initial costs.

Richard L. Flower, P. E., LEED Green Associate
Senior Structural Engineer
Complere Engineering Group, Inc.