Civil and Structural Engineering, Computational Mechanics, Mechanics of Materials, Building and Construction
9
Scopus Publications
62
Scholar Citations
5
Scholar h-index
3
Scholar i10-index
Scopus Publications
Numerical Modelling of concrete beams strengthened with co-cured CFRP plates with a mussel shell modified epoxy (MME): An XFEM-CZM traction–separation framework with experimental works validation Syahrin Azhar, Sugiman Sugiman, Zaim Omar, Hilton Ahmad Multiscale and Multidisciplinary Modeling Experiments and Design, 2026 Concrete beam strengthening using externally bonded CFRP remains a key method for extending service life and capacity. A reliable, mechanism-aware prediction of load-bearing capacity is still required for design. A finite-element framework was therefore established and validated to predict the flexural response of beams strengthened with CFRP plates co-cured with a mussel-shell-modified epoxy (MME) adhesive. The model was implemented in ABAQUS/CAE using a traction separation law (TSL) framework. XFEM simulated concrete cracking, while CZM captured the debonding behaviour at the CFRP and adhesive with concrete interface using the same TSL parameters. Material and interface properties were obtained independently and utilised. The influences of CFRP bonded length, MME volume fraction, and pre-loading before strengthening were examined. Validation employed load–displacement curves, failure modes, and dedicated stress-distribution studies that mapped peel and shear along the plate ends and across the interface. It was found to transition with bonded length from tip-driven shear–tension to flexural debonding; pre-loading introduced carried crack damage that elevated local interface stresses and advanced the onset of debonding. The inclusion of MME enhanced composite action and delayed failure, with moderate filler content performing best; however, excessive content (≈10%) degraded adhesive properties. The predictions of ultimate load showed close agreement with tests: most debonding-controlled cases lay within ≤ 10%, the remainder within 10–20%, and a single boundary-dominated short-plate case exceeded 20%. The framework provides mechanistically transparent stress insight and numerically reliable capacity prediction for CFRP/MME strengthening, supporting sustainable and optimised strengthening configurations.
Compressive Strength–Water Absorption Behaviour of Concrete with Coal Bottom Ash as Sand Replacement across Water–Cement Ratios Ku Muhammad Firdaus Ku Meh, Zaim Omar, Suleyman Khalif Mohamed Journal of Building Material Science, 2026 Coal bottom ash (CBA) is produced in large quantities by coal-fired power plants. It offers a viable opportunity for sustainable utilisation as a partial replacement, especially for fine aggregate in concrete. However, its porous morphology and surface characteristics complicate controlling water demand and optimising concrete performance. In this research, the synergistic effects of water–cement (WC) ratio (0.40, 0.45, and 0.50) with CBA contents (0%, 10%, and 20% from mass of sand) on compressive strength and water absorption of concrete at 28 and 56 curing ages. Increasing the WC ratio and CBA content generally reduced compressive strength and increased water absorption, whereas extended curing improved strength while lowering absorption. Target performance was achieved with up to 20% CBA when the WC ratio was maintained within 0.40–0.45, defining a practical mix-design window. A strong inverse correlation was observed between compressive strength and water absorption at WC = 0.40–0.45 (R2 ≈ 0.92–0.95), whereas the relationship weakened at WC = 0.50 (R2 ≈ 0.82–0.83) due to increased pore connectivity and variability associated with excess mixing water. The reliability of these correlations was further confirmed through statistical error analysis, with low RMSE, RAE, and RRMSE values, particularly at WC = 0.45, indicating high predictive accuracy and minimal deviation between measured and predicted strengths. In contrast, higher error metrics at WC = 0.50 reflect reduced model robustness. These findings establish design boundaries that can be adopted in practice to valorise CBA while safeguarding performance, thereby informing greener specifications and guiding future standards for the use of industrial by-products in concrete.
Structural Interaction Between Woven Kenaf FRP Plates and Notched Concrete Beams Under Flexural Loading Zaim Omar, Hilton Ahmad, Sugiman Sugiman, Hazrina Mansor, Suleyman Khalif Mohamed, Ku Muhammad Firdaus Ku Meh Journal of Infrastructure Preservation and Resilience, 2025 Concrete is widely recognised for its durability and high compressive strength, making it one of the most utilised construction materials globally. However, structural elements such as beams are often subjected to defects, including notches and cracks, which reduce their load-carrying capacity and necessitate effective strengthening solutions. Fibre Reinforced Polymer (FRP) systems have been extensively applied to enhance structural performance. Kenaf FRP (KFRP) is a promising natural alternative due to its high tensile strength and sustainability. This study examines the flexural performance of notched concrete beams reinforced with woven KFRP plates, aiming to enhance load-carrying capacity through experimental testing and validation via three-dimensional finite element analysis. The research involves three standardised notched-depth beam designs, with 18 specimens tested under four-point bending. Failure modes and ultimate load capacities were analysed, revealing dominant mechanisms such as flexural cracking and KFRP rupture. The results indicate that KFRP strengthening increased the ultimate load capacity by up to 200% compared to unstrengthened beams. Additionally, the Extended Finite Element Method (XFEM) with traction-separation laws was employed to predict flexural strength, demonstrating a strong correlation with experimental results, with mean variances below 6%. The numerical approach is a reliable predictive tool for estimating the flexural strength of notched beams reinforced with natural FRPs. Experimental and numerical findings confirm that KFRP plates significantly improve the flexural strength of notched concrete beams, highlighting their potential as an effective and sustainable retrofitting solution for deteriorated concrete structures.
Experimental investigations of strengthened beam with co-cured carbon FRP and mussel shell-modified epoxy Syahrin Azhar, Sugiman Sugiman, Zaim Omar, Hilton Ahmad Ain Shams Engineering Journal, 2025 Traditional strengthening materials, such as carbon fibre reinforced polymer (CFRP) plates bonded with synthetic fillers, often rely on non-renewable resources and may have limited environmental compatibility. Thus, mussel shells with a high content of calcium carbonate particles act as rigid particles and alternatives to synthetic filler counterparts added in epoxy resin, enhancing the mechanical properties of filled epoxy. This paper aims to investigate the improvement of flexural resistance by incorporating mussel shell powder as a bio-filler of epoxy resin (hereafter referred to as mussel shell-modified epoxy, MME), which was then used as the bonding agents with CFRP sheets via co-cured technique as a beam strengthening method. A four-point bending test was conducted to investigate four parametric studies, i.e., CFRP bonded lengths (Series A), mussel shell powder volume fraction (Series B) and different percentages of pre-load applied on concrete beams with different bonding agent types, i.e., MME (Series C) and neat epoxy resin (Series D). A 7.5% volume fraction of MME and the most extended CFRP sheet enhanced the ultimate load with deflection (associated with concrete ductility) of the strengthened plain beams by 108% and 58%, respectively, compared to the control beam. Interestingly, up to 66% improvement was observed in Series C by applying pre-load at 60% of the control beam’s ultimate load, comparing beams strengthened with MME to those using neat epoxy (Series D). In this test, pre-loading was applied by subjecting the concrete beams to 60% of their ultimate capacity using a Universal Testing Machine (UTM) before applying CFRP sheets, ensuring consistent initial stress conditions for reliable comparison. Hence, MME is a viable bio-filler incorporated in epoxy resin to enhance co-cured CFRP as a strengthening material.
Utilizing XFEM model to predict the flexural strength of woven fabric Kenaf FRP plate strengthened on plain concrete beam Zaim Omar, Sugiman Sugiman, Hazrina Mansor, Hilton Ahmad Case Studies in Construction Materials, 2023 The evolution of advancing computing technology has encouraged the use of finite element analysis to require constitutive models, mostly adopted extensive experimental datasets. Nevertheless, fewer material properties are required within the bilinear traction-separation relationship incorporated with the XFEM technique and require fewer computation efforts due to the energetic approach simulation. This study used ABAQUS CAE 2021 to predict the flexural strength of plain concrete beams strengthened with Kenaf Fibre Reinforced Polymer (KFRP) plates under a four-point bending test, later validated with experimental datasets. The varying parameters, including woven fabric architectures, lengths, widths, and plate thickness, were considered. The results demonstrated that the consistency proposed modelling technique in this study well-captured failure modes and crack development as experimental observations. All models demonstrated an increase in peak load, and a comparison of load-deflection profiles was made between the numerical FEA modelling with the experimental works. The peak load discrepancies between the numerical outputs and the experimental datasets were found to be less than 12% in all testing series. Despite promising findings, stress analysis on peel and shear stresses associated with failure modes exhibited was performed. It was found that KFRP ruptures occurred due to peel stress peak at plate mid-span, while shear mode failure demonstrates concentrated peel stress (to lesser extent shear stress) at KFRP edge tip. Hence, a more unified approach is promoted to require only two material properties (preferably independently measured values). This approach enables a designer to choose the optimum FRPs size using the current modelling tool, substantially reducing laborious and expensive experimental setup.
The effects of woven fabric Kenaf FRP plates flexural strengthened on plain concrete beam under a four-point bending test Zaim Omar, Sugiman Sugiman, Mustafasanie M. Yussof, Hilton Ahmad Case Studies in Construction Materials, 2022 Kenaf fibre possesses excellent tensile strength and elongation at break and is suitable to replace synthetic fibres as reinforcing materials in FRPs composites. This research is aimed to develop an experimental programme to study the behaviour of strengthened concrete beams externally bonded woven fabric Kenaf FRP (KFRP) plates. A four-point bending test was conducted to explore the effects of KFRP plate variation, such as woven fabric architectures, KFRP lengths, KFRP widths, and plate thickness (with cross-ply layers) on plain concrete beams. KFRP plate significantly improved the ultimate load, deflection at peak, stiffness, and performance factor of the strengthened plain beams when kenaf volume fraction and KFRP plate dimensions increased. The best effect to increase plain concrete beam performance was seen in specimen D-PX4 (Series D) with ultimate load, deflection and stiffness are 84 %, 50 % and 36 % with an average performance factor is 103 % compared to control beam. Thus, the flexural strengthening of a plain concrete beam using a KFRP plate is found to be a good alternative technique.
Predicting the Flexural Behaviour of CFRP-Strengthened Concrete Beam using Combined XFEM and Cohesive Zone Model Zaim Omar, Sugiman Sugiman, Mustafasanie M. Yusoff, Hilton Ahmad Journal of Applied Science and Engineering, 2022 This paper presents the numerical strength prediction of externally carbon fibre reinforced polymer (CFRP)- strengthened concrete beams using a traction-separation law. From reported experimental observations, the externally CFRP-strengthened concrete beams are prone to exhibit mixed-mode cohesive failure within the adhesive layer before beam separation. Testing series comprised of different strengthening schemes and CFRP plate length indicated that all specimens failed in cohesive delamination (debonding). This study performed a numerical modelling framework by using a combination of extended finite element method (XFEM) within the concrete beam and cohesive zone model (CZM) within the adhesive layer to explicitly demonstrate debonding phenomenon as seen in experimental observations. The results showed that the modelling technique was able to capture the debonding failure and the crack propagation of the concrete beam, consistent with experimental observations. Hence, the combination of the XFEM-CZM approach yields good agreements with experimental datasets. It was found that discrepancies of maximum load-bearing capacity between numerical modelling and previous experimental work are below 17 % were found in all testing series. However, due to the unavailability of fracture energy properties of tested concrete, the current approach used values of similar concrete grade from other literature. It is expected that better results would be obtained if the fracture energy of the investigated concrete beam was independently measured.
Numerical modelling of foamed concrete beam under flexural using traction-separation relationship H. Ahmad, S. Sugiman, Z.M. Jaini, A.Z. Omar Latin American Journal of Solids and Structures, 2021 The aim of the current project is to carry out the FEA framework for predicting the flexural strength of notched foam concrete tested under three-point bending following the conducted experimental set-up. The investigated testing series have a variation of notch size opening in the foamed concrete beam. The Traction-separation relationship was used as a constitutive model to incorporate independent material properties and used in the modelling framework. Modelling techniques of 2D XFEM and CZM were adopted and later expanded to 3D XFEM models. Good agreement was found between the predicted structure response and experimental observation for all the investigated models. Crack was initiated at the crack tip and propagated to the beam edge under the applied load. It was found that the average discrepancies below 20% were found within XFEM techniques. Less agreement was found using the CZM models, partly due to the simplification of the adopted failure path. The modelling framework implemented in this project is potentially used as a predictive tool in estimating the flexural strength of the concrete beam with notches.
RECENT SCHOLAR PUBLICATIONS
Numerical Modelling of concrete beams strengthened with co-cured CFRP plates with a mussel shell modified epoxy (MME): An XFEM-CZM traction–separation framework with … S Azhar, S Sugiman, Z Omar, H Ahmad Multiscale and Multidisciplinary Modeling, Experiments and Design 9 (1), 103 , 2026 2026.0
Experimental investigations of strengthened beam with co-cured carbon FRP and mussel shell-modified epoxy S Azhar, S Sugiman, Z Omar, H Ahmad Ain Shams Engineering Journal 16 (10), 103563 , 2025 2025.0 Citations: 6
Structural Interaction Between Woven Kenaf FRP Plates and Notched Concrete Beams Under Flexural Loading Z Omar, H Ahmad, S Sugiman, H Mansor, SK Mohamed, KMFK Meh Journal of Infrastructure Preservation and Resilience 6 (1), 25 , 2025 2025.0 Citations: 3
Optimisation and prediction modeling of hardened concrete characteristics incorporating coal bottom Ash (CBA) via the response surface methodology (RSM) KMF Ku Meh, SS Mohd Zuki, HA Algaifi, Z Omar, S Shahidan, ... Multiscale and Multidisciplinary Modeling, Experiments and Design 7 (6 … , 2024 2024.0 Citations: 7
Utilizing XFEM model to predict the flexural strength of woven fabric Kenaf FRP plate strengthened on plain concrete beam Z Omar, S Sugiman, H Mansor, H Ahmad Case Studies in Construction Materials 18, e02056 , 2023 2023.0 Citations: 11
Material Properties and Fracture Energy of Kenaf FRP Composites Z Omar¹, S Sugiman, MM Yussof Proceedings of the First Mandalika International Multi-Conference on Science … , 2023 2023.0 Citations: 5
The effects of woven fabric Kenaf FRP plates flexural strengthened on plain concrete beam under a four-point bending test Z Omar, S Sugiman, MM Yussof, H Ahmad Case Studies in Construction Materials 17, e01503 , 2022 2022.0 Citations: 15
Predicting the flexural behaviour of CFRP-strengthened concrete beam using combined XFEM and cohesive zone model Z Omar, S Sugiman, MM Yusoff, H Ahmad Journal of Applied Science and Engineering 25 (6), 1077-1090 , 2022 2022.0 Citations: 15
Strength Predictions of RC Beam with Various Percentages of Tension Reinforcements H Ahmad, Z Omar, K Supar, NY Zainun
MOST CITED SCHOLAR PUBLICATIONS
The effects of woven fabric Kenaf FRP plates flexural strengthened on plain concrete beam under a four-point bending test Z Omar, S Sugiman, MM Yussof, H Ahmad Case Studies in Construction Materials 17, e01503 , 2022 2022.0 Citations: 15
Predicting the flexural behaviour of CFRP-strengthened concrete beam using combined XFEM and cohesive zone model Z Omar, S Sugiman, MM Yusoff, H Ahmad Journal of Applied Science and Engineering 25 (6), 1077-1090 , 2022 2022.0 Citations: 15
Utilizing XFEM model to predict the flexural strength of woven fabric Kenaf FRP plate strengthened on plain concrete beam Z Omar, S Sugiman, H Mansor, H Ahmad Case Studies in Construction Materials 18, e02056 , 2023 2023.0 Citations: 11
Optimisation and prediction modeling of hardened concrete characteristics incorporating coal bottom Ash (CBA) via the response surface methodology (RSM) KMF Ku Meh, SS Mohd Zuki, HA Algaifi, Z Omar, S Shahidan, ... Multiscale and Multidisciplinary Modeling, Experiments and Design 7 (6 … , 2024 2024.0 Citations: 7
Experimental investigations of strengthened beam with co-cured carbon FRP and mussel shell-modified epoxy S Azhar, S Sugiman, Z Omar, H Ahmad Ain Shams Engineering Journal 16 (10), 103563 , 2025 2025.0 Citations: 6
Material Properties and Fracture Energy of Kenaf FRP Composites Z Omar¹, S Sugiman, MM Yussof Proceedings of the First Mandalika International Multi-Conference on Science … , 2023 2023.0 Citations: 5
Structural Interaction Between Woven Kenaf FRP Plates and Notched Concrete Beams Under Flexural Loading Z Omar, H Ahmad, S Sugiman, H Mansor, SK Mohamed, KMFK Meh Journal of Infrastructure Preservation and Resilience 6 (1), 25 , 2025 2025.0 Citations: 3
Numerical Modelling of concrete beams strengthened with co-cured CFRP plates with a mussel shell modified epoxy (MME): An XFEM-CZM traction–separation framework with … S Azhar, S Sugiman, Z Omar, H Ahmad Multiscale and Multidisciplinary Modeling, Experiments and Design 9 (1), 103 , 2026 2026.0
Strength Predictions of RC Beam with Various Percentages of Tension Reinforcements H Ahmad, Z Omar, K Supar, NY Zainun
