Story drift is controlled by ASCE 7 for most structures for two primary reasons:
1- avoidance of P-delta effects associated with large story drift
2- damage to nonstructural components including cladding, interior walls, etc.
The ASCE 7 committee believes that P-delta issues are rare for single story structures because of their general light weight and also that Section 12.8.7 provides adequate protection against P-delta instability for such structures. However, excessie dadmage to nonstructural elements is still of concern.
To appropriately design walls, partitions and similar elements to withstand large design drifts, it would be necessary to isolate these elements from story drift. In the case of interior partitions, this could be accomplished by cantilevering interior partitions from the floor, an not attaching them to the roof, so that lateral drift of the roof does not deform the wall. Cladding would have to be attached to the frame such that lateral frame drift would not place damaging shear deformations on the cladding. Ceilings would have to have sufficient clearance from walls and partitions so that they will not pound against the walls/partitions when the roof drifts.
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Ronald Hamburger, SE
Consulting Principal
Simpson Gumpertz & Heger
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Original Message:
Sent: 12-13-2023 02:46 AM
From: Seham Elsaeed
Subject: Allowable Story Drift - ASCE 12.12-1, footnote c
I have a question about the allowable story drift in ASCE 7 Table 12.12-1. Footnote c has the following:
There shall be no drift limit for single-story structures with interior walls, partitions, ceilings, and exterior wall systems that have been designed
to accommodate the story drifts. The structure separation requirement of Section 12.12.3 is not waived.
Can someone explain what "that have been designed to accommodate the story drifts" means? Specifically for a steel structure - what needs to be incorporated into the design? and really we no need to check drift for single story strcuture ?
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Best Regards
Dr. Seham A. Elsaeed
Engineering Technical Manager
PHD –civil engineering (structural "Steel" engineering)
Kirby Building Systems- Egypt
EXT.1132-TEL 965 60695560
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