Structural Engineering and Mechanics

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Proposals for flexural capacity prediction method of externally prestressed concrete beam

  • Yan, Wu-Tong (School of Civil Engineering, Beijing Jiaotong University) ;
  • Chen, Liang-Jiang (China Railway Economic and Planning Research Institute Co., Ltd.) ;
  • Han, Bing (School of Civil Engineering, Beijing Jiaotong University) ;
  • Wei, Feng (China State Railway Group Co., Ltd.) ;
  • Xie, Hui-Bing (School of Civil Engineering, Beijing Jiaotong University) ;
  • Yu, Jia-Ping (School of Civil Engineering, Beijing Jiaotong University)
  • Received : 2022.03.25
  • Accepted : 2022.05.21
  • Published : 2022.08.10
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Abstract

Flexural capacity prediction is a challenging problem for externally prestressed concrete beams (EPCBs) due to the unbonded phenomenon between the concrete beam and external tendons. Many prediction equations have been provided in previous research but typically ignored the differences in deformation mode between internal and external unbonded tendons. The availability of these equations for EPCBs is controversial due to the inconsistent deformation modes and ignored second-order effects. In this study, the deformation characteristics and collapse mechanism of EPCB are carefully considered, and the ultimate deflected shape curves are derived based on the simplified curvature distribution. With the compatible relation between external tendons and the concrete beam, the equations of tendon elongation and eccentricity loss at ultimate states are derived, and the geometric interpretation is clearly presented. Combined with the sectional equilibrium equations, a rational and simplified flexural capacity prediction method for EPCBs is proposed. The key parameter, plastic hinge length, is emphatically discussed and determined by the sensitivity analysis of 324 FE analysis results. With 94 collected laboratory-tested results, the effectiveness of the proposed method is confirmed, and comparisons with the previous formulas are made. The results show the better prediction accuracy of the proposed method for both stress increments and flexural capacity of EPCBs and the main reasons are discussed.

Keywords

Acknowledgement

The authors would like to acknowledge the following financial supports: the Funds of China Railway Economic Planning and Research Institute (Grant No. 2021BSH01); Project of Science and Technology Research Development Plan of China Railway (Grant No. K2021G013 and N2021G046); Project from Key Laboratory of Transport Industry of Bridge Detection Reinforcement Technology (Beijing) (Grant No. C21M00030).

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