Analytical and numerical investigation of concrete long-term effects on flexural performance of reinforced concrete members

Abstract

The flexural behaviour of reinforced concrete beams is a complex phenomenon due to the presence of creep, shrinkage and concrete cracking. These long-term phenomena lead to increased deflection with time, which cause long-term serviceability concern. Although shrinkage and creep may cause time-dependent deflection and a significant decrease in moment capacity and stiffness with time in flexural RC members, little research has focused on their effects. This, in part, can be attributed to the demanding nature of creep and shrinkage in concrete when experimentally testing their effects on the flexural performance of RC members. This study aimed at analytically and numerically investigating the long-term effects of concrete on the flexural performance of RC members. An analytical investigation on the effect of creep and shrinkage of the concrete of a previous experimentally tested simply supported RC beam on deflection, moment capacity, and stiffness of the member is conducted using ES 2-2015, ACI 318-19, and MC-2010 design codes. The analysis was undertaken by varying performance affecting parameters, including beam dimensions, reinforcement ratios, and loading types. Furthermore, a numerical simulation of the same beam was generated to examine long-term deflection and cracking patterns. Comparisons of analytical and numerical results with experimental was made. From the analytical results of each code, total long-term deflection under two-point loads at 150 days was 4.05mm, 3.39 mm, and 4.207mm according to ES 2-2015, ACI-318-19, and MC-2010 design codes, respectively. As a result, all codes gave a relatively good fit to the experimental results. Besides, in the 3D nonlinear finite element simulation, ABAQUS, total long-term deflection was 3.679mm. Accordingly, the simulation deflections result showed a good fit to that of the experimental deflection results. The study also revealed that beam dimension, reinforcement ratio, and loading types affect the deflection of RC beams when shrinkage and creep of the concrete are incorporated. Additionally, the study showed that shrinkage and creep affect moment capacity and stiffness of RC beam. In conclusion, while evaluation of the deflection calculation expression is considered in different design codes, it seems like the existing codes need to be improved the expression for long-term deflection by conducting further experimental investigation.