Title: Deflections Considering Twist Angles for Curved Concrete Girders

Author(s): Yin Shen, Taiyu Song, Guoping Li, CS Walter Yang, and David W. Scott

Publication: Structural Journal

Volume: 116

Issue: 4

Appears on pages(s): 155-168

Keywords: curved girders; effective stiffness; post-cracking deformation; prestressed concrete; torsional stiffness; twist angle

DOI: 10.14359/51715566

Date: 7/1/2019

Abstract:
Horizontally curved concrete girder bridges have been widely used in urban viaducts and overpasses across the world. When designing these structures, it is necessary to estimate the maximum deflections under service loads to satisfy requirements of the serviceability limit state. Because of twist due to torsion in curved concrete girders, the maximum deflection needs to take into account the effect of torsional twist, which has not been considered in previous research. Based on the concept of effective torsional stiffness, a new method is proposed for calculating post-cracking twist angles in curved concrete girders. The proposed method in combination with the effective moment of inertia method can accurately predict maximum deflections in curved concrete girders. The simplicity of the proposed method is illustrated in an example. The calculated central deflections and twist angles are compared with experimental data obtained from previous tests that cover curved box-section and solid-section non-prestressed and prestressed concrete beams. The proposed method provides satisfactory predictions in terms of twist angles until the first yielding of reinforcement. The variations between the calculated and measured twist angles and maximum deflections are within ±10% and ±20%, respectively. The results of this study indicate that deflection formulas from the ACI 318-14 Code and the AASHTO LRFD Bridge Design Specifications may produce non-conservative results for curved concrete girders under certain loading conditions.