Title:
Concrete Q & A: Torsion Calculations for Hollow Sections
Author(s):
James K. Wight
Publication:
Concrete International
Volume:
27
Issue:
7
Appears on pages(s):
68
Keywords:
DOI:
Date:
7/1/2005
Abstract:
ACI 318-05, Section 11.6.1—Threshold torsion, appears to have inconsistent requirements for hollow sections when compared to Section 11.6.2 —Calculation of factored torsional moment. Section 11.6.1 instructs the designer to replace Acp with Ag (see Fig. 1), while Section 11.6.2.2 forbids the designer from replacing Acp with Ag. Further, although R11.6.1 states that test data show that hollow beams have a lower cracking torque than solid sections with the same outside dimensions, R11.6.2.2 states, “The replacement of Acp with Ag, as in the calculation of the threshold torque for hollow sections in 11.6.1, is not applied here. Thus, the torque after redistribution is larger and hence more conservative.” The cracking torque is clearly much larger when one uses Acp versus Ag—are the two sections correct?