Strengthening of Continuous Reinforced Concrete Beams Using Steel Reinforced Grout

Abstract

This study investigated the effectiveness of steel-reinforced grout (SRG) in enhancing the flexural performance of continuous reinforced concrete (RC) beams. Twenty medium-scale, two-span RC beams were designed, fabricated, and experimentally tested to assess the influence of various parameters, including steel reinforcement ratio, SRG layers, SRG steel fabric density, strengthening length, strengthening location, type of fabric, and the presence of a column stump. Experimental results confirmed the efficacy of SRG strengthening in improving beam stiffness and load-carrying capacity but at the cost of reduced ductility. Load-carrying capacity improvements ranged from 24% to 104%. The number of SRG layers had a significant impact on load-carrying capacity, particularly for beams with low steel reinforcement ratios. Low-density SRG showed superior bonding with the concrete substrate, leading to enhanced strengthening effects compared to high-density SRG. The strengthening system substantially enhanced the energy absorption capacity of the beams, especially with low-density SRG. The presence of a column stump slightly reduced the effectiveness of SRG strengthening with negligible other effects. Strengthening only the critical span (60% of the full span) achieved load-carrying capacity close to that of full-span strengthening, offering advantages in material use, time, and labor. Strengthening only the top or bottom zones resulted in lower load- carrying capacity increases compared to strengthening both top and bottom. Beams with low-density SRG primarily failed due to fiber fracture or concrete cover separation, indicating strong concrete-SRG adhesion. However, high-density SRG beams failed prematurely due to debonding, likely caused by fewer voids in the high-density fabric. A numerical model was developed to simulate the experimentally tested beams using finite element modeling. After validation, the model was used to conduct a parametric study and expand the experimental investigation by studying a wider range of parameter combinations. A mathematical model to estimate the debonding strain of SRG, which is essential for evaluating the ultimate moment capacity of SRG-strengthened RC beams, was proposed using genetic algorithm techniques. The proposed model surpassed existing models in accuracy and inclusion of important variables.