curtain wall deflection

huangyhg

curtain wall deflection
what horizontal, deflection criteria is recommended for exterior, glass, curtain walls to resist lateral wind forces?  l/600? 480? 360?
on a slight tangent, what would you recommend for the following:  (all due to lateral wind forces)
-exterior structural concrete masonry also supporting gravity loads.
-exterior concrete or brick masonry veneer.
usually l/600 is reserved for masonry or veneer, curtain wall, l/360 should be adequate, however they might have criterion to follow.
almost all of the aluminum curtain walls that i have designed deflection has been specified to be l/175 or 3/4" whichever is less
aisc's steel design guide #3, "serviceability design considerations", has l/240 listed as a deflection limit for wind forces in table 1 for exterior walls with brittle finishes.
i design my curtain walls for l/360 generally unless they support brick veneer which gets a deflection criterion of l/600.  
what exactly is "empirical design of masonry" as per mbc 2003? if you use the ncma software for a masonry load bearign wall design, would you consider it as a special design or an empirical design?
for glass and al. curtain wall, currently, the most often used deflection criteria is l/175 w/ 3/4" max for spans less than 13'-6" and l/340+1/4" for spans greater than 13'-6".  the old l/175 , 3/4" max was an old window criteria intended for use w/ single lites.  it is too conservative for modern curtian wall design, especially when coupled with c&c wind pressures.
for out of plane, i would use l/180 or so for curtain wall (more strict depending on the finish), l/300 or so for cmu and brick. i think a lot of people use different amounts. i usually check total deflection as well as the ratio.
you could multiply the wind load by 0.7 in ibc 2000 for checking deflections under c&c , i haven't checked if you still can in 2003.