Comparative study of strategies for creep simulation in the calculation of second-order effects in reinforced concrete columns

Resumo

This dissertation project aims to investigate the effects of creep in reinforced concrete columns, considering different strategies. With the democratization of computer access and the evolution of structural models, most part of building projects developed nowadays relies on more comprehensive structural models, which incorporate non-linear behaviors in their analysis, either through simplified or refined approaches. However, despite the evolution of these models, the simulation of the effects of creep is an aspect that still needs improvement. Creep is defined as the phenomenon of increasing deformations in concrete over time when subjected to constant stress. The topic is especially relevant in reinforced concrete columns, where the phenomenon can cause increased forces as well as increased second-order moments. The complexity of the creep phenomenon leads to simplified methods dominating the scenario, although there is still a shortage of studies on practical methodologies applicable in projects. In this context, the main objective of this work is to conduct a comparative analysis between commonly employed methods in practice for simulating creep with more refined models. The strategies considered are the Approximate Method of Additional Eccentricity e_{cc}; Standard-Column Method coupled with M, N, 1/r Diagrams considering creep effects through extended stress-strain curve; General Method coupled with M, N, 1/r Diagrams also considering creep effects through extended stress-strain curve; and Mathematical Model with analytical incorporation of the time variable. This study aims to formulate algorithms, to produce different models and simulations, to compare the results obtained by the different analyzed methods, and, if necessary, to propose practical solutions to achieve more reliable results. In this way, this study seeks to highlight both the effectiveness and limitations of the analysis strategies considered, aiming to contribute to the improvement of safety in implementing these strategies, especially those presented by Brazilian standards.