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Re: [SEAOC] Glazing support

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I would agree that this may be a good idea, however, in many cases drift
governs in sizing moment frames, therefore reducing allowable drift could
double the required moment of inertia. If a residential building is
utilizing several moment frames this could increase costs significantly. So
a certain amount of judgement is placed on the engineer . I have seen
glazing systems that have a receiving channel that leaves a 7/8" gap all
around the frame except at the sill. This is not necessarily a deflection
space as there are sheet metal screws attaching the chanel to the glazing

I am curious if window manufacturers provide systems with a true deflection
space to account for lateral movements? I know they can be made for
vertical deflections.

Also, I am curious about the reliabilty of calculating plywood diaphragm
and shear wall deflections as there are numerous redundancies and 
secondary effects (such as finishes, unaccounted for stiffnesses around
openings, damping by partitions), in addition to the fact that the formulas
for diaphragm deflection is somewhat empirical.  I have heard that
limitations on plywood aspect ratios will be reduced in future codes, which
means even more moment frames will be used in residences.

I am also curious if the UBC aspect ratios are corelated to the UBC
standards deflection formula?

Jeff Smith

>I have tried to limit story drift where large glass store-front and 
>glass walls (custom homes) are desired, to 0.0025h. I know that this is 
>twice as stiff as code allows, but since there is virtually no room for 
>flexibility in large glass panels I felt that less damage would incur in 
>a stiffer system. I am not as concerned where smaller windows are used - 
>such as in most residential. Here I design for 0.005h deflection (story 
>Hope this helps
>Dennis Wish PE