Tension bracing for steel studs

[OlyEng]

I am using tension only bracing to resist lateral forces for a mezzanine framed with light gage steel studs. What is the best way to hand calc the rigidity of the braced wall, to distribute lateral forces to walls of different lengths. Thanks!

 

[DaveAtkins]

Load each wall with a 1 kip horizontal force and calculate the force in the tension strap. The elongation of the tension strap = PL/AE. Convert the elongation of the strap into a horizontal movement at the top of the wall using trigonometry. It's been awhile since I did one of these projects, but I seem to recall that the stiffness of each wall is inversely proportional to its length (i.e., a 20' long wall is half as stiff as a 10' long wall). DaveAtkins

 

[OlyEng]

Dave,
Do I consider the length for the PL/AE calc to be the total strap length? My strap will be attached to each stud in the wall system as it crosses the studs(16"o.c.), will this possibly reduce the effective length for elongation? It seems to me that the presence of the studs would add rigidity to the system. Thanks.

 

[RG88]

When I perform this type of analysis, I assume that the studs do not provide any rigidity as the stud to top/bottom plate connections cannot resist bending moments. It isn't overly conservative to analyze it this way. To account for bending resistance of each stud along the strap is a statically indeterminate headache and I would expect that it does not provide much given the work involved.