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:
122
Issue:
1
Appears on pages(s):
199-212
Keywords:
cracked; deflection; effective moment of inertia; integration; partially prestressed; prestressed concrete.
DOI:
10.14359/51742153
Date:
1/1/2025
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 momentdeformation 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.