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Modeling and comparative analysis of sustainable cotton rope confinement: Full vs. STrip wrapping for enhanced concrete strength and ductility
(2025-07-01)
Saingam, Panumas
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Gadagamma, Chaitanya Krishna
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Hussain, Qudeer
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Hlaing, Hnin Hnin
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Suwannatrai, Rawirot
The rise of natural FRPs as ecological alternatives to synthetic ones has highlighted the need for studies on partial confinement using cotton ropes, which offer cost-effective, low-carbon solutions with high rupture strain. Unlike full confinement, partial confinement through cotton rope strips can efficiently strengthen deteriorated concrete sections with reduced material usage. Despite possessing several advantages, the partial confinement by cotton on concrete has not been investigated. This study addresses the gap by investigating the performance of cotton rope strips and developing analytical models to predict their structural impact. This study tested cylindrical concrete specimens of two strengths, strengthened with cotton rope in either complete wrapping (Group 1) or strip wrapping (Group 2). Each group was further divided by concrete strength and included one unstrengthened specimen, and three strengthened with one, two, or three layers of cotton rope. Experimental results revealed that cotton rope wraps effectively confined the concrete, enhancing load-bearing capacity and improving ultimate compressive strength by 9.97–152.10 % and ultimate strain by 188.00 % to 1488.89 %. The compressive stress vs. strain behavior exhibited an initial stiff elastic ascent followed by a parabolic transition. The second branch of the response, either ascending or descending, was significantly improved with an increased confinement ratio. Type-I failure was characterized by an ascending second branch in the compressive stress vs. strain curve, while Type-II failure exhibited a descending second branch. Four specimens demonstrated Type-I failure (L-2F, L-3F, H-3F, and L-3S), predominantly in full configurations and with lower unconfined compressive strength. The modulus of the second branch improved with an increased confinement ratio, transitioning from Type-II to Type-I failure near a ratio of approximately 0.50. Regression analysis provided equations of various key points along the compressive response with R² values greater than 0.90, highlighting a strong dependence on the confinement ratio. The Popovics model effectively predicted the first part of the compressive response, with predicted curves closely matching experimental results.
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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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Corrigendum to “Seismic strengthening of heritage masonry buildings using fiber-reinforced paint: Numerical validation and shake table testing for enhanced energy dissipation and safety” [J. Build. Eng. 101 (2025) 111824] (Journal of Building Engineering (2025) 101, (S2352710225000609), (10.1016/j.jobe.2025.111824))
(2025-05-01)
Htet, Phyo Min
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Ejaz, Ali
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Gadagamma, Chaitanya Krishna
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Hussain, Qudeer
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Saingam, Panumas
The authors regret that the affiliation of the fifth author (Wasim Khaliq) was wrong in the published article. The correct affiliation is “National Institute of Transportation, National University of Sciences and Technology (NUST), Islamabad, Pakistan.” The acknowledgement section should be updated by including the last line in the acknowledgement. The revised acknowledgement should read as: This project received the Fundamental Fund (FF) from Thailand Science Research and Innovation for the fiscal year 2024 (Contract No. 128/2567). Thanks are also extended to the Asian Institute of Technology (AIT) for supporting test facilities. The authors are also thankful to Dr. Yamamoto Kenjiro and Dr. Shanthanu Rajasekharan from Aster Co. Ltd., Japan., for support and guidance in executing this research. The authors would like to apologise for any inconvenience caused.
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Seismic strengthening of heritage masonry buildings using fiber-reinforced paint: Numerical validation and shake table testing for enhanced energy dissipation and safety
(2025-05-01)
Htet, Phyo Min
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Ejaz, Ali
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Gadagamma, Chaitanya Krishna
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Hussain, Qudeer
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Saingam, Panumas
This research aimed to strengthen heritage masonry buildings using fiber-reinforced paint (FRP) and evaluate seismic responses, including the Arias intensity scale, peak acceleration, peak displacement, lateral drift, and dissipated energy. In the numerical phase, the prototype model was studied using the Applied Element Method (AEM) and similitude law, resulting in a well-performing scaled model with error percentages of approximately 5 % for element results and 4 % for spring results. This validated the model's accuracy, leading to its adoption for experimental work. The experimental phase involved shake table testing of the scaled models, revealing that the unreinforced model (URM) collapsed at run 44, whereas the FRP-retrofitted specimen collapsed at run 52. Cracks in the FRP-retrofitted specimen began at run 39, compared to run 10 in the URM, with the FRP-retrofitted specimen arch masonry roof remaining undamaged prior to collapse. The FRP-retrofitted specimen demonstrated superior seismic performance, with an Arias intensity scale 3.67 times higher, base shear over 400 % greater, and lateral drift 10.89 times higher than the URM, indicating its ability to resist significant displacement and deform plastically. Additionally, the FRP-retrofitted specimen exhibited stable, wider hysteretic loops, leading to 6.1 times more energy dissipation than the URM, thereby offering enhanced safety for occupants.
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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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Large rupture strain cotton ropes hybridized with affordable fiberglass chopped strand mat sheets for enhanced compressive behavior of reinforced concrete columns
(2024-11-15)
Saingam, Panumas
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Gadagamma, Chaitanya Krishna
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Hussain, Qudeer
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Ejaz, Ali
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Hlaing, Hnin Hnin
The hybrid confinement system combines various fiber types within a single matrix, allowing for the adjustment of volumetric ratios to optimize confinement performance. Synthetic FRPs are more expensive and have a higher carbon footprint due to significant CO<inf>2</inf> emissions during production. In response, this study presents an innovative hybrid confinement approach using two natural materials: cotton ropes and FSMS (CFS) to improve concrete strength and ductility. Specimens, standardized at 300 mm height and 150 mm diameter with longitudinal steel bars and stirrups, were divided into two groups based on CFS configurations. The stress-strain response of CFS-confined concrete displayed distinctive behavior: an initial parabolic phase leading to peak compressive stress (ultimate strength), followed by a linearly degrading phase. Across all subgroups, CFS confinement significantly enhanced ultimate strength and corresponding compressive strains, with Subgroup 2A achieving the highest improvements of 246 % in ultimate strength and 1477 % in strain. Moreover, the ductility gain was reported as high as 20 for CFS-confined concrete. A non-proportional enhancement in the compressive behavior was observed with the increase in confinement ratio. Predictive models were developed for the idealized two-branch response of CFS-confined concrete, encompassing expressions based on nonlinear regression for ultimate strength, corresponding strain, ultimate strain, and elastic modulus. Two existing models were modified to trach each branch of the response. Integrating these two adjusted models closely replicated the experimental compressive curves.

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