Title: Immediate Deflection of Cracked Prestressed Concrete Beams Based on Integration of Curvature

Author(s): Wassim Nasreddine, Adi Obeidah, Peter H. Bischoff, and Hani Nassif

Publication: Structural Journal

Volume:

Issue:

Appears on pages(s):

Keywords: cracked; deflection; effective moment of inertia; integration; partially prestressed; prestressed concrete

DOI: 10.14359/51742153

Date: 8/5/2024

Abstract:
Prediction of immediate deflection is evaluated for cracked prestressed concrete members using integration of curvature. Integration accounts for changes in member stiffness and strand eccentricity along the member length when applicable. Several approaches are considered including a bilinear moment-deformation response and those using an effective moment of inertia based either on an effective prestress moment defined by an effective eccentricity of the prestress force or an offset in the cracked response with tension stiffening. Comparison is also made with deflection computed directly assuming a uniform member stiffness based on the effective moment of inertia at the critical section where the moment is greatest. Results are evaluated using an extensive database for beams either fully or partially prestressed. The beams are simply supported under two-point loading and have a straight tendon profile with constant eccentricity. Integration of curvature is observed to improve prediction of immediate deflection in general and depends not only on the approach used but on several factors that include the cracking moment, elastic modulus of concrete, and the effect of approximating uncracked section properties with gross section properties.