Non-iterative moment capacity equation for reinforced concrete beams with external post-tensioning

The stress of unbonded steel in post-tensioned concrete beams at the ultimate stage is needed to determine their moment capacity, but it is difficult to accurately predict the stress of external posttensioning steel. This is because the unbonded steel stress is governed by total steel elongation, which depends on the beam deflection and other interrelated variables. The bulk of the previously developed analytical methods are applicable only for internal tendons encased in concrete. Given the lack of analytical models for externally post-tensioned beams, in this study, a simplified non-iterative equation for the stress at ultimate in external tendons or other steel materials is developed. During this process, flexural responses of yield and ultimate moments and their corresponding deflections are also predicted. A major effort is made to simplify such a process and propose a generalized non-iterative moment capacity equation for reinforced concrete beams with external post-tensioning. Copyright © 2014, American Concrete Institute.