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

• Main Authors: Luo, Da, Zhang, Zhongwen, Li, Bing
• Other Authors: School of Civil and Environmental Engineering
• Format: Article
• Language: English
• Published: 2023
• Subjects: Engineering::Civil engineering; Continuous Beams; Moment Redistribution
• Online Access: https://hdl.handle.net/10356/170190
• Institution: Nanyang Technological University

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 x/d, equations as a function of εt for predicting the βu of continuous beams under the two loads are proposed, respectively.