Title:
Moment Redistribution in Unbonded Prestressed Concrete Members: Proposed Modification of ACI Equation
Author(s):
Tiejiong Lou, Chengming Peng, Di Min, and Wei Sun
Publication:
Structural Journal
Volume:
117
Issue:
6
Appears on pages(s):
71-80
Keywords:
moment redistribution; numerical analysis; relative rigidity; unbonded tendon
DOI:
10.14359/51725891
Date:
11/1/2020
Abstract:
The ACI 318 code uses sole parameter εt (net strain in extreme tensile steel) to calculate the allowable moment redistribution in continuous prestressed members. However, this parameter is section-dependent, while moment redistribution is member-dependent. Therefore, the ACI 318 code may not be reasonable for the quantification of moment redistribution. This paper evaluates the moment redistribution against εt in continuous unbonded prestressed concrete (UPC) members, focusing on the effect of relative rigidity represented by q1/q2 (q1 and q2 are tensile reinforcement indices at critical sagging and hogging sections, respectively). Numerical evaluations are conducted on two-span UPC members with q1/q2 ranging from 0.46 to 2.24. It is shown that q1/q2 has tremendous effects on moment redistribution in UPC members, but these effects are neglected in the ACI 318 code. A modification of the ACI equation is proposed by introducing the parameter q1/q2 to quantify the moment redistribution in UPC members.
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