COLD FORMED STEEL DESIGN with RAMADVANSE

[PT999]

I am using Ramsadvance to design a cold formed steel stud wall for shear, axial and lateral loads

What is the correct Material to enter in Ramadvance
MarinoWare catalog says material is A653 33 ksi, but that's not one of the choices, yet the software has cold formed SSMA sections, so one of the listed material choices must be right

Apart from a satisfactory frame analysis with RamAdvance, how are screw connections analyzed. For example, say you want to use a #10 screw. How do you figure how many? Are there charts for this?

Any good (and simple) software for cold formed steel design? I think I am doing this the hard way!

 

[DaveAtkins]

I do a lot of cold formed steel design, mostly by hand. The only time I use RISA-3D to analyze cold formed steel is when the structure is indeterminate (e.g., a two story tall stud, or a complicated fascia).
But notice I said I only use the computer to ANALYZE cold formed steel. Marino Ware, or Dietrich, or any other major cold formed steel supplier has tables with section properties and moment capacities for all depths and gauges of studs, as well as tables giving allowable stud heights based on wind load, as well as tables giving allowable axial load based on wind load and stud height. They also publish values for screws, based on diameter and stud gauge, as well as weld capacities.

DaveAtkins

 

[scottiesei]

I'm with Dave. My CFS design has all been by hand and with the tables. Also, the SSMA has some great publications on their web site.

 

[PT999]

Ok, I see the tables, but none of them deal with shear wall design. Thats why I started the Ram analysis. So assuming I pick a suitable section for axial and wind load, how are shear walls figured. Is it just selecting size and number of screws to match shear force?

 

[scottiesei]

In Florida, the bulding code has tables for the shear. Try checking your building code.

 

[DaveAtkins]

IBC Chapter 22 covers shear walls constructed of cold formed steel studs with either GWB or OSB sheathing.

DaveAtkins

 

[UcfSE]

Be careful using published tables for flexural design. You need to pull out the effective properties and check the stud moment capacity using the AISI code. SSMA tables, as well as tables by other manufacturers, often have the value for "Ma" published, allowable moment. This value does not take into account lateral-torsional buckling. You will need to check that yourself either with software or the AISI code. Note also that many programs will not check web crippling. This is very important and needs to be checked anytime it can occur. Because light-gauge steel has such thin walls, problems that we rarely check when designing hot-rolled steel with the AISC need to be routinely checked when designing cold-formed steel.

That said, I do a lot of CFS design as well. I use RISA occasionally to check complex framing and obtain reactions. Otherwise we use a simple program that checks studs per AISI. It is not published any more or I would give you a link.

When checking connections, it is easiest to do those by hand. Some programs may handle this but I haven't run into any. Most manufacturers publish allowable shear and pullout values for their screws. Again, you may also find screw capacity with the AISI code, chapter E. Usually I find that is best since you aren't constrained to any particular brand of screw and you don't have to worry about possible bogus test results. The AISI code will also provide a means for checking block shear, pull-over (different from pull-out) and other failure modes as well as give you the proper LRFD factors or safety factors to use. Be conservative with screw connections. A few more screws won't kill anyone and will help cya when they miss some or strip some holes.

The code will also list common steel materials along with properties. In your program, it is more important that you have the proper yield and tensile strength than the designation of the material. For 43-mil and thinner, use Fy=33ksi and Fu=45ksi. For 54-mil and thicker, use Fy-50ksi and Fu=65ksi. These are most common.

Basically if you are in cold-formed steel design, you need to get the AISI code.

 

[haynewp]

Usually I have studs with drywall at the interior and sheathing on the exterior, and I treat the flanges as braced for bending. Specify maximum blocking (or other type of bracing) interval if sheathed on only one side.

 

[STR04]

Also look at ASCE 7-02, section A.9.8 & Table A.9.8.6.5.