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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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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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Reduction of Damage Concentration in Seismic Retrofitted RC Building with Friction Dampers
(2024-01-01)
Sirinipitakul, Terapat
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Suwannatrai, Rawirot
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Hlaing, Hnin Hnin
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Saingam, Panumas
Because of their lack of lateral force resistance or energy dissipation capability, reinforced concrete (RC) structures have suffered significant damage in previous earthquakes. There is a demand to develop and improve the seismic performance of vulnerable existing RC buildings, particularly those not initially designed for seismic events or designed to an outdated seismic standard. Seismic retrofit of RC buildings using friction dampers is an innovative method to improve the seismic performance of the structures. In this study, nonlinear response history analysis was performed to investigate and compare the seismic performance of retrofitted buildings. The numerical results suggest that the maximum displacement was substantially improved after retrofitting the existing RC building with friction dampers. The damage concentration of the retrofitted buildings with friction dampers is reduced significantly when compared to the existing RC buildings.
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Seismic Retrofit of Shear Wall Medium-Rise RC Building with Buckling-Restrained Braces
(2024-01-01)
Hlaing, Hnin Hnin
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Suwannatrai, Rawirot
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Tammajak, Nontaphat
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Kriangkriatkong, Phusana
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Nakkahnong, Apisak
Thailand was impacted by the earthquake both directly and indirectly. Many structures in Chiang Rai were damaged by the large Mae Lao earthquake in 2014. This makes the government recognize how crucial it is to develop earthquake-resistant structures for public safety. Structures in many locations are required to consider designing more earthquake-resistant structures due to calculations made regarding the building structure’s ability to ensure the earth-quake’s vibration. Several medium-rise buildings in Bangkok have been required to improve their seismic performance to fulfill the new standard and to protect them from future earthquakes. Therefore, this study investigates the validation of updated design code and efficiency of retrofitting an existing shear wall medium-rise RC building that was planned with seismic concern but not in accordance with more modern code regulations using buckling restrained braces (BRBs). In addition, the possible locations of retrofitting BRBs are investigated. A typical 36-story RC shear wall residential building in Bangkok is used as the target building. An equivalent linear static analysis is performed to investigate the seismic performance of the target building. The results indicate that the seismic performance of the retrofitted building with BRB is improved when compared to the non-retrofitted building, and the retrofitted shear wall medium-rise RC building with the damper location close to the shear wall is the most efficient when compared to other locations.
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Enhancing the flexural behavior of brick masonry walls with ferrocement overlays and low-cost anchors
(2023-12-01)
Saingam, Panumas
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Hlaing, Hnin Hnin
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Suwannatrai, Rawirot
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Ejaz, Ali
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Hussain, Qudeer
This study presents an innovative approach to enhance the flexural capacity of cement-clay interlocking (CCI) brick walls using ferrocement jackets with an expanded wire mesh. The investigation involved 15 CCI brick walls subjected to flexural load testing, exploring various mesh sizes and anchor configurations on single and dual sides. The results revealed that while the primary failure mode involved dry joint opening and subsequent ferrocement debonding in the strengthened walls, effective anchorage mechanisms delayed dry joint opening until debonding occurred. The reinforced walls exhibited improved peak load capacity, notably in dual-sided reinforcement cases. With plastering on both sides and supplemented with anchors, an improvement of up to 221% in flexural capacity was obtained. The study emphasizes the influence of wire mesh size on anchorage effectiveness and its correlation with debonding susceptibility. Additionally, the moment-curvature analysis demonstrated resilient, ductile responses in load-bearing characteristics, with occasional abrupt declines due to ferrocement jacket debonding. Unlike control walls, the strengthened walls exhibited strains exceeding yield thresholds, indicating enhanced structural performance.
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