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Structural Engineering and Mechanics Volume 85, Number 5, March10 2023 , pages 679-691 DOI: https://doi.org/10.12989/sem.2023.85.5.679 |
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Moment redistribution of RC continuous beams: Re-examination of code provisions |
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Da Luo, Zhongwen Zhang and Bing Li
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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 (pu) for some beams deviate significantly from the specified values of various codes. This paper examines the applicability of the provisions on pu 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 pu to a certain extent, where the ratio of tensile reinforcement ratio at intermediate support to tensile reinforcement ratio at midspan (ps1/ps2) and load type are crucial parameters to consider. The specific combination of these two parameters may make the codes overestimate or significantly underestimate the pu. 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 pu. The yield conditions are investigated, and an empirical judgment equation is proposed. In addition, the influence laws of the critical parameters on pu have been further proved by theoretical derivation. Finally, due to pt is found to have a better linear correlation with Bu than xu/d, equations as a function of pt for predicting the pu of continuous beams under the two loads are proposed, respectively. | ||
| Key Words | ||
| ACI 318-19; continuous beams; Eurocode 2; moment redistribution; yield conditions; yield state of both critical sections | ||
| Address | ||
| Da Luo: School of Civil Engineering, Chang'an University, Xi'an, 710061, P.R. China Zhongwen Zhang: Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, Nanjing, 210000, P.R. China Bing Li: School of Civil and Environmental Engineering, Nanyang Technological University, 639798, Singapore | ||