Abstract
Thirteen (13) reinforced concrete (RC) columns in a chemical processing plant were inspected due to concerns over the structural deterioration of existing RC structures in a highly corrosive environment. To assess the remaining strength, structural integrity, and durability of the deteriorated RC structures, proper inspection procedures and prediction models were utilized.
Four (4) non-destructive testing (NDT) techniques were used to conduct a condition assessment on the RC columns. The NDT results provided data on the concrete compressive strength and uniformity, rebar size and arrangement, and corrosion levels of the existing RC columns. The rebound hammer test results indicated a reduction in concrete compressive strength at the top of columns 2, 3, and 12, with average strengths of 22 MPa, 23 MPa, and 21 MPa, respectively. Similarly, the bottom regions of columns 5, 6, 8, 9, and 13 showed average compressive strengths of 24 MPa, 23 MPa, 23 MPa, 20 MPa, and 13 MPa. The remaining columns 1, 4, 5, 7, 10, 11, and 12 exhibited average compressive strengths greater than 25 MPa throughout their lengths. Based on combined data from the rebound hammer test, UPV test, and SONREB (Sonic Rebound) technique, column 2 was identified as the worst case and selected for Finite Element Model (FEM) analysis using Abaqus (2022 HF4) [1]. The data from column 2 were used to develop a FEM to simulate the performance of RC columns under corrosion and varying concrete strength grades (20 MPa at the top, 25 MPa in the middle, and 27 MPa at the bottom).
Corrosion of embedded reinforcement leads to the formation of expansive corrosion products, causing cracking and spalling of the concrete cover. This process reduces the bond between the steel and concrete and ultimately reduces the strength of the concrete. Detailed analyses revealed a decrease in reinforcement tensile stress from 155.82 MPa to 153.29 MPa in corroded columns and a reduced ability to resist compressive forces due to decreased rebar diameters. Concrete strength degradation impacts load-carry capacity, with stiffness analysis indicating a reduction from 4098.3 MPa to 3981.6 MPa in corroded columns. Despite a relatively small difference in axial displacement, corroded columns exhibit increased stiffness,
Numerical Investigation of Structural Integrity of Corroded Concrete Columns
Ludere T.T. 200910731
iii ABSTRACT | Dissertation
compromising resilience to deformation and energy absorption. The study highlights a critical risk of structural failure under heavy loads, as evidenced by the decreased residual strength from 9356.86 kN to 9098.18 kN.
While considerable research has been conducted on the effects of corrosion on RC columns, there is a significant gap in understanding the long-term performance and durability of RC columns in highly corrosive environments such as chemical processing plants. Current models often fail to account for the complex interactions between varying degrees of concrete strength degradation and corrosion levels. This study aims to fill this gap by integrating detailed NDT data with advanced FEM analysis to provide more accurate predictions of structural performance under realistic operational conditions.
Numerical modelling is highly advantageous as it provides information on the residual compressive strength of the existing RC columns. This tool can simulate various corrosion scenarios, prevent unforeseen failures, optimize designs, and predict the load capacity of already corroded RC columns, thus reducing potential risks in chemical processing plants.
Keywords: Reinforced concrete (RC) columns, Concrete, Corrosion, Structural integrity, Non-destructive testing (NDT), Rebound hammer test, Ultrasonic Pulse Velocity (UPV) test, SONREB technique, Finite Element Model (FEM), Abaqus