Interstory Drift effect on multi-story wall panels

[JCWilson]

Can anyone elaborate on the effects of interstory drift on multi-story wall panels, i.e. "components and cladding"? I am involved in the design and fabrication of prefabricated wall panels (generally light gage steel frames with a variety of finishes, i.e. brick, EIFS, GFRC, etc.) that typically measure 10' wide by 30'-40' tall. Our projects are generally east coast USA.

The effects of interstory drift over multiple floors is of concern, but this information is often not provided in the plans, nor even calculated for the Eastern US. Performing a complex analysis is out of the question for a subcontractor such as us.

ASCE 7-98 9.5.3.7 and BOCA 1996 1610.4.5.1 both touch on the subject, but I am not sure how to best apply this to a wall panel system system. The full effect of following this procedure is very difficult to apply to a wall panel without becoming prohibitively expensive.

Has anyone experienced similar design problems and can you elaborate on a way to address this? Has anyone seen how multi-story wall panels respond to a seismic event?

 

[JAE]

I don't have a lot of experience with multi-story wall panels as you describe them, but if the engineer of record is requiring you to provide an "in-place" design of a wall panel, it is his responsibility to provide those inter-story drifts so you can properly detail your floor/roof to panel connections.

If you absolutely cannot get this info from the engineer, then you are stuck with presuming the building will drift the maximum allowed by the code.

 

[coco1953]

Thinking in a practical way, if the structural engineer who prepared the plans has not worried in specifying the drifts for which your panels should be designed, you should not either unless you could be liable for the damages they suffer in case of a shake. If you are, you could ask the engineer to establish them, but I find it will be very difficult for you to design panels that dont get cracked in that case, specially if they involve rigid materials. Any rigid wall panel will be more rigid than any framed structure, and will be damaged unless the building has many and long shearwalls, that I dont think is the case. Beside, the effect of non structural building components such as the multy story wall panels you mention should have been taken in account in the design of the building if their rigitidy can interfer with the lateral behavior of the building, mostly producing plan torsions that change the distribution of lateral forces. Anyway, dont worry too much, for yours will not be the only cracked panels in the neighborhood. I have read that a serious shake in the eastern US will bring to earth a significant proportion of old and new poorly designed buildings, but the damages will have to be regarded as "natural consequences" by the structural engineers.

 

[cyak]

I would say that if the panel can withstand an interstory drift D = 0.005 H, where H is floor height (or any two levels between which the drift is measured), it will be OK. For the type of panel you are describing many codes would prescribe a limit of D to D < 0.007 H since a panel in light steel is not very sensitive to shear deformations as a masonry infill.

Thus if your story height is 10 ft, then the panels should be able to accomodate a shear deformation of 0.6 inches in their plane. I think this would be enough.