Structural Engineering and Mechanics

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Moment redistribution of RC continuous beams: Re-examination of code provisions

  • Da Luo (School of Civil Engineering, Chang'an University) ;
  • Zhongwen Zhang (Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University) ;
  • Bing Li (School of Civil and Environmental Engineering, Nanyang Technological University)
  • Received : 2022.05.03
  • Accepted : 2023.02.16
  • Published : 2023.03.10
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Abstract

Many codes allow designers to use the bending moment diagram computed by elastic analysis and modify it by a certain amount of moment redistribution (MR) to account for plastic behaviour of continuous beams. However, several researchers indicated that the MR at the ultimate limit state (𝛽u) for some beams deviate significantly from the specified values of various codes. This paper examines the applicability of the provisions on 𝛽u in ACI 318-19 and Eurocode 2 through numerical investigations and comprehensively explores the influencing factors. The results show that some parameters not considered in those codes influence 𝛽u to a certain extent, where the ratio of tensile reinforcement ratio at intermediate support to tensile reinforcement ratio at midspan (𝜌s1/𝜌s2) and load type are crucial parameters to consider. The specific combination of these two parameters may make the codes overestimate or significantly underestimate the 𝛽u. On the other hand, the yield state of both critical sections is found to have an important influence on the influence degree of each parameter on 𝛽u. The yield conditions are investigated, and an empirical judgment equation is proposed. In addition, the influence laws of the critical parameters on 𝛽u have been further proved by theoretical derivation. Finally, due to 𝜀t is found to have a better linear correlation with 𝛽u than xu/d, equations as a function of 𝜀t for predicting the 𝛽u of continuous beams under the two loads are proposed, respectively.

Keywords

Acknowledgement

The research described in this paper was financially supported by the Fundamental Research Funds for the Central Universities, CHD (300102282106). The authors wish to express their gratitude for this financial support.

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