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Evaluating the shear capacity of reinforced concrete beams retrofitted with hybrid FRP composite techniques: experimental and analytical study
(2026-07-01)
Joyklad, Panuwat
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Chatveera, Burachat
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Sua-Iam, Gritsada
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Chaimahawan, Preeda
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Suthumma, Chisanuphong
This study investigates the shear performance of reinforced concrete (RC) beams strengthened with externally bonded hybrid fiber-reinforced polymer systems. The strengthening materials include mild steel strips, glass chopped strand mat (GCSM) fiber-reinforced polymer (FRP) composites, natural basalt fiber-reinforced polymer (BFRP) composites, and hybrid combinations of GCSM and BFRP. The hybrid systems pair low-strain GCSM composites with higher-strain natural BFRP to improve both strength and ductility. Eleven RC beams were tested and compared to a control specimen that lacked shear reinforcement over half the span. All strengthened beams showed substantial improvements over the unstrengthened control (35.49 kN). Peak loads ranged from 59.94 kN to 144.86 kN, corresponding to increases of approximately 69–308% relative to the control. In term of deflections again peak load, strengthening increased deflections by roughly 4.4–10.5 times versus the control beam. Strip orientation and layering strongly influenced crack redistribution and energy dissipation. The hybrid GCSM–BFRP systems provided a balanced improvement in strength and post-peak behavior.These results indicate that steel-strip and composite-based strengthening approaches offer affordable and effective solutions for retrofitting shear-deficient RC elements, particularly in post-disaster or resource-limited settings.
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Enhancing Strength and Ductility of Rubberized Concrete Using Low-Cost Glass Jackets
(2026-04-01)
Saingam, Panumas
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Noman, Muhammad
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Chatveera, Burachat
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Sua-Iam, Gritsada
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Mehmood, Tahir
This study examines the compressive behavior and analytical modelling of natural and rubberized concretes (RuC) confined with low-cost glass chopped-strand mat (GCSM) jackets. A total of forty-two cylindrical specimens were tested under axial compression to assess the influence of rubber particle size, confinement configuration, and the number of GCSM layers. The RuC mixes were prepared by replacing 20% of fine aggregate by volume with crumb rubber of two size fractions: coarse (2.0 mm, retained on #10 sieve) and fine (0.425 mm, retained on #40 sieve). Both full- and strip-wrapping schemes were applied using two, four, and six layers of GCSM. The results demonstrated that GCSM jackets significantly enhanced the mechanical performance of both NAC and RuC specimens. Full wrapping provided the highest confinement efficiency, increasing compressive strength by up to 115% for NAC and 90% for RuC, while the ultimate axial strain increased by more than 1300% compared with unconfined specimens. Strip wrapping also improved performance, producing strength gains of 25–45% and strain increases of 250–500%. Analytical stress–strain models were developed through regression analysis, showing strong correlation with the experimental results (R2 = 0.80–0.99). The proposed GCSM jacket system demonstrates high potential as a sustainable and economical alternative for strengthening and retrofitting rubberized concretes, offering improved ductility and energy absorption while supporting circular material utilization. It is noted that the confinement ratio, size of rubberized aggregates, and their percentage replacement of rubberized aggregates should be consistent with the values used in this work in order to use the proposed analytical expressions.
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From Experiment to Prediction: Machine Learning Solutions for Concrete Strength Assessment with Steel Clamps
(2026-02-01)
Saingam, Panumas
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Chatveera, Burachat
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Sua-Iam, Gritsada
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Chaimahawan, Preeda
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Suthumma, Chisanuphong
This study examines the confined compressive strength (Fcc) of circular, square, and rectangular column geometries under varying confinement conditions. Results indicate that circular columns have the highest Fcc values, exceeding those of square and rectangular shapes. Increased confinement through clamps significantly enhances compressive strength. Five machine learning models, Linear Regression, Decision Tree, Random Forest, AdaBoost, and Gradient Boosting, were used to predict Fcc based on geometric and confinement parameters. Linear Regression and Decision Tree models achieved moderate predictive performance, with R2 values of 0.84 and 0.83, respectively, and relatively higher error measures (RMSE, MAE, and MAPE), indicating limited ability to capture complex nonlinear relationships in the data. In contrast, ensemble-based methods demonstrated superior performance. The Random Forest model improved the coefficient of determination to 0.90 while substantially reducing all error metrics, reflecting enhanced generalization through bagging. The boosting-based approaches yielded the best results, with AdaBoost achieving the highest R2 value of 0.99 and the lowest RMSE, MAE, and MAPE among all models, followed closely by Gradient Boosting with an R2 of 0.98. These results confirm that ensemble learning techniques, particularly boosting algorithms, yield more accurate and robust predictions than single learners for the problem studied. Data visualization techniques, including Regression Error Characteristic curves (REC) and SHapley Additive exPlanations (SHAP) value analysis, highlighted model performance and feature importance, emphasizing the roles of confinement and geometry in compressive strength. This research demonstrates the potential of machine learning to optimize structural engineering design and suggests further exploration of alternative shapes and confinement strategies to enhance structural integrity.
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Sustainable Reinforcement Methods for Brick Masonry Walls: An Experimental and Finite Element Analysis Approach
(2025-07-01)
Mehmood, Tahir
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Abid, Muhammad Amer
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Chatveera, Burachat
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Sua-Iam, Gritsada
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Saingam, Panumas
This study investigates the enhancement of axial and shear strength in brick masonry walls reinforced with steel and fiberglass meshes. The novelty of this study lies in its thorough evaluation of various reinforcement types and their influence on both axial and shear strength, offering valuable insights to enhance the performance of brick masonry structures. By using steel and fiberglass meshes for reinforcement, the study promotes the use of durable materials that can extend the lifespan of brick masonry structures, reducing the need for frequent repairs and replacements. The findings reveal that double-layer steel mesh delivers the highest strength, effectively reducing brittleness and improving deformation capacity in both single- and double-brick walls. Specifically, single-brick walls exhibited increases in compressive strength of 38.8% with single-layer steel mesh, 31.2% with fiberglass mesh, and 19.7% with plaster. In contrast, double-brick walls showed enhancements of 73.6% with double-layer steel mesh and 43.5% with fiberglass mesh. For shear strength, single-brick walls improved by 115.1% with single-layer steel mesh, 91.3% with fiberglass mesh, and 42.1% with plaster, while double-brick walls experienced increases of 162.7% with double-layer steel mesh and 132.5% with fiberglass mesh. Additionally, Abaqus modeling under axial and diagonal compression closely matched experimental results, revealing less than a 10% discrepancy across all reinforcement types.
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Evaluating Failure Patterns and Bursting Loads in Concrete Segmental Bridge Piers: A Comprehensive Study
(2025-06-01)
Suparp, Suniti
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Ejaz, Ali
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Gadagamma, Chaitanya Krishna
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Saingam, Panumas
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Hussain, Qudeer
This study presented an experimental and numerical investigation focused on pier segments of segmental bridge types. The pier segments were constructed to represent Lak Si Overpass Highway Route No. 304, Thailand. The experimental program included five pier segments with similar reinforcement details but varying concrete strengths. The numerical work validated the finite element model (FEM) using experimental results and conducted a parametric study to assess the impact of steel reinforcement variation and concrete compressive strength on the bursting capacity of pier segments. Key findings included a consistent failure pattern characterized by a prominent vertical crack and concrete crushing at the bottom, particularly in specimens with lower concrete strength. The bursting loads exhibited a decrease corresponding to a reduction in compressive strength, with up to a 20% decrease observed when strength was reduced by 20%. The finite element analysis (FEA) results slightly surpassed experimental findings, yet the marginal discrepancies confirmed the accuracy of the advanced tool for engineering nonlinear analysis (ATENA) computer program in predicting bursting forces. The parametric study highlighted a substantial increase in bursting loads with variations in concrete strength and the number of steel reinforcement layers, with a non-proportional relationship between bursting load and concrete strength.
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Innovative Approaches to RC Deep Beam Strengthening: Evaluating Low-Cost Glass Fiber Wraps Against Traditional CFRP Solutions
(2025-03-01)
Saingam, Panumas
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Ejaz, Ali
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Gadagamma, Chaitanya Krishna
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Hussain, Qudeer
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Sua-iam, Gritsada
This study evaluates the performance of lightweight aggregate deep beams strengthened with low-cost glass fiber-reinforced polymer composite (Lo-G) wraps as an alternative to expensive synthetic fiber-reinforced polymers (FRPs). The investigation includes side-bonded and fully wrapped configurations of Lo-G wraps, alongside carbon FRP (CFRP) strips for comparison. The experimental results show that epoxy-based anchors provided significantly better resistance against de-bonding than mechanical anchors, improving beam performance. Strengthening with Lo-G wraps resulted in a peak capacity increase of 17.0% to 46.9% for side-bonded beams in Group 2, 10.5% to 41.4% for fully wrapped beams in the strip configuration in Group 3, and 15.4% to 42.7% for CFRP strips in Group 4. The ultimate deflection and dissipated energy were also improved, with dissipated energy increases of up to 264.6%, 322.3%, and 222.7% for side-bonded and fully wrapped Lo-G wraps and CFRP strips, respectively. The side-bonded configuration with two or three Lo-G wraps, supplemented by epoxy wraps, outperformed fully wrapped 250 mm strips in peak capacity, with peak capacity improvements of up to 46.9%. However, beams with mechanical anchors showed poor performance due to premature debonding. They rely on friction and expansion within the concrete to resist pull-out forces. If the surrounding concrete is not strong enough or if the anchor is not properly installed, it can lead to failure. Additionally, reducing strip spacing negatively impacted performance. Lo-G wraps showed an 8.5% higher peak capacity and 32.8% greater dissipated energy compared to CFRP strips. Despite these improvements, while Lo-G wraps are a cost-effective alternative, their long-term performance remains to be investigated. None of the existing models accurately predicted the shear strength contribution of Lo-G wraps, as the lower elastic modulus and tensile strength led to high deviations in prediction-to-experimental ratios, underscoring the need for new models to assess shear strength.
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Hybrid B-CSM Composites Strengthening Approach for Improved Stress–Strain Behavior of Concrete Columns and Development of Analytical Models
(2025-02-01)
Thansirichaisree, Phromphat
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Mohamad, Hisham
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Zhou, Mingliang
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Ejaz, Ali
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Saingam, Panumas
The brittle behavior of concrete under axial compressive loading has been a persistent issue. This study investigates the effectiveness of a hybrid Basalt-E-glass confinement (B-CSM) in improving the compressive behavior of concrete. The B-CSM confinement demonstrates a considerable improvement in ultimate strength and strain capacity by over 250 and 500%, respectively, making it a favorable solution for enhancing the ductility of concrete structures. Specimens at 18.43 MPa unconfined strength, confined with 3-layer B-CSM, demonstrated a 258% ultimate strength enhancement. For 24.43 MPa specimens, the same confinement resulted in a 207% increase in ultimate strength. Specimens with an initial ultimate strain of 18.43 MPa, when confined with 3-layers, showed a notable 516% increase. Likewise, for 24.43 MPa specimens, the same confinement led to a significant 395% improvement in ultimate strain. The use of B-CSM confinement is also effective in terms of cost compared to synthetic fiber-reinforced polymer jackets, and its availability is widespread. Existing analytical models for fiber-reinforced polymer confinement were evaluated, and it was found that these models could not predict the ultimate strength and strain of B-CSM-confined concrete. Therefore, this study proposes a unique regression-based approach for predicting the various points of the compressive stress vs. strain curve of B-CSM confinement. These points are then used to trace the complete stress vs. strain curve, which matches closely with experimental results. This work contributes to the development of new design recommendations for B-CSM confined concrete structures, which can enhance the performance of concrete structures and potentially reduce construction costs.
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Machine Learning and Regression Models for Evaluating Ultimate Performance of Cotton Rope-Confined Recycled Aggregate Concrete
(2025-01-01)
Rodsin, Kittipoom
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Ejaz, Ali
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Wang, Huaping
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Saingam, Panumas
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Joyklad, Panuwat
This study investigates the use of cotton ropes (CRs) as a sustainable and cost-effective substitute for synthetic fiber-reinforced polymers for concrete confinement, offering significant environmental benefits such as lower CO<inf>2</inf> emissions and reduced energy consumption. The work evaluates the effectiveness of CR strips for confining concrete, including scenarios with recycled concrete aggregates (ReCA). Compressive strength improvements varied among specimens, with Specimen I-3F showing a 140.52% increase and Specimen II-3F achieving a 46.67% improvement. Strip configurations for Type I recycled aggregate concrete (RAC) outperformed full wraps on Type II RAC, exemplified by Specimen I-3S’s 84.51% improvement. Ultimate strain enhancements ranged from 915% to 4490.91%, driven by the significant rupture strain of cotton rope confinement. For Type I RAC, complete wrapping significantly outperformed strip configurations by 56%, 50%, and 32% in ultimate strength improvement for 1, 2, and 3 layers, respectively. The confinement ratio, varying from 0.10 to 0.70, greatly influenced the compressive behavior, with compressive strength normalized by unconfined strength increasing consistently with the confinement ratio. A minimum confinement ratio of roughly 0.40 is required to achieve an increasing second part in the compressive behavior. The initial parabolic branch was modeled using Popovics’ formulation, revealing an elastic modulus approximately 20% lower than ACI 318-19 predictions. The second branch was described using a linear approximation, and nonlinear regression analysis produced expressions for key points on the idealized compressive curve, enhancing model accuracy for CR-confined RAC. The (Formula presented.) values for the nonlinear regression analysis performed on experimental results were greater than 0.90. This study highlights the effectiveness of neural network expressions to predict the compressive strength of CR-confined concrete. A strength reduction (ratio of full wrap and strip wrap height CRs) factor of 0.67 was proposed and used for strip-wrapped specimens. It was seen that the neural network models also predicted the compressive strength of partially wrapped specimens with reasonable accuracy using the strength reduction factor.
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Corrigendum to ‘Enhancing compressive behavior of concrete with novel low-cost hybrid passive confinement including large rupture strain cotton ropes: Experimental findings and a design-oriented model’ [Case Stud. Constr. Mater. 21 (2024) e03496] (Case Studies in Construction Materials (2024) 21, (S2214509524006478), (10.1016/j.cscm.2024.e03496))
(2024-12-01)
Saingam, Panumas
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Hussain, Qudeer
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Ejaz, Ali
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Nawaz, Adnan
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Joyklad, Panuwat
The authors regret that the fifth author's name was incorrect in the published article. The correct name of the fifth author as “Panuwat Joyklad” The acknowledgement section should be updated by including the last line in the acknowledgement. The revised acknowledgement should read as: This research is a result of the project entitled “Development of a Novel, Low-cost and High Performance Hybrid FRP Composites for Waste Aggregate Concrete for Sustainable Cities Grant NO.RE-KRIS/ FF67/023” by King Mongkut's Institute of Technology Ladkrabang (KMITL), which has been received funding support from the NSRF. The APC was funded by King Mongkut's Institute of Technology Ladkrabang Research Fund. The authors would like to apologise for any inconvenience caused. DOI of original article: < https://doi.org/10.1016/j.cscm.2024.e03496>
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Towards sustainable construction: Harnessing potential of pumice powder for eco-friendly concrete, augmented by hybrid fiber integration to elevate concrete performance
(2024-12-01)
Farooq, Umar
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Rizwan, Muhammad
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Khaliq, Wasim
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Ejaz, Ali
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Saingam, Panumas
This study investigates the innovative use of industrial waste pozzolana, specifically pumice powder (PP), as a partial replacement for cement, combined with hybrid fibers in concrete. Seven formulations varying PP content from 10 % to 35 % were tested, identifying 15 % PP as optimal. PP improved porosity due to its fineness, leading to better homogeneity, a refined microstructure, and an optimum compressive strength of 28.8 MPa with reduced permeability, enhancing durability. Hybrid fibers, including steel fibers (SF) from waste tires and polypropylene fibers (PF), improved toughness, ductility, and resistance to brittle failure. Tests on hybrid fiber-reinforced concrete (HyFRC) mixes with 1 % and 2 % hybrid fibers showed up to an 18.09 % increase in compressive, tensile, and flexural strengths. Energy dissipation in compressive response improved by 544.20 %, while flexural and splitting responses increased by up to 299.65 % and 208.57 %. Durability assessments in hydrochloric (HCl) and sulfuric acid (H<inf>2</inf>SO<inf>4</inf>) exposure revealed the synergy of fibers and PP enhanced resistance to chemical degradation, with high PF mixes losing as little as 0.04 % strength. Scanning electron microscopy (SEM) confirmed a dense, well-bonded matrix with reduced porosity. Analytical characterizations of mixtures such as energy dispersive x-ray spectroscopy (EDX) were studied. Regression models developed using Popovic's and Mander's models, accurately predicted HyFRC stress-strain behavior, closely aligning with experimental results. The integration of PP and hybrid fibers not only improved mechanical properties but also extended service life in harsh environments, offering a cost-effective, sustainable concrete solution.

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