UBC 97 laeral displacement

[ahmedhegazi]

According to UBC97 clause 1630.9.1

Determination of (Delta)S. A static, elastic analysis of the
lateral force-resisting system shall be prepared using the design
seismic forces from Section 1630.2.1. Alternatively, dynamic
analysis may be performed in accordance with Section 1631.
Where Allowable Stress Design is used and where drift is being
computed, the load combinations of Section 1612.3 shall be used.
The mathematical model shall comply with Section 1630.1.2. The
resulting deformations, denoted as (Delta)S, shall be determined at all
critical locations in the structure. Calculated drift shall include
translational and torsional deflections.


this part refer to service load combinations where the Earthquake Force needed to calculate the displacement should be based on service load combination (E/1.4)

i have seen many copies of UBC 97 that refer to Section 1630.1.3 (Ultimate combinations,1.0E) used to calculate drift!

what do you think gentlemen.

 

[ARKeng]

....Where Allowable Stress Design is used and where drift is being
computed, the load combinations of Section 1612.3 shall be used....

My 97 UBC says 1612.2, not 1612.3 here. To me that says (and it matches my memory from when I used to use the 97 UBC), use the Strength design LC's for all drift numbers. I know it's certainly that way in the ASCE 7 codes (at least since -02).