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All Journal Civil Engineering Journal
Abbas, Rafaa M.
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Civil Engineering, Building, Construction & Architecture

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Journal : Civil Engineering Journal

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Pre- and Post-Cracking Resistance of Steel Fiber Reinforced Concrete Flexural Members with GFRP Bars Mohammed, Shatha D.; Abbas, Rafaa M.; Salman, Hamza M.; Oukaili, Nazar K.; Allawi, Abbas A.
Civil Engineering Journal Vol. 11 No. 9 (2025): September
Publisher : Salehan Institute of Higher Education

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.28991/CEJ-2025-011-09-023

Abstract

This research investigates the pre- and post-cracking resistance of steel fiber-reinforced concrete specimens with Glass Fiber Reinforced Polymer (GFRP) bars subjected to flexural loading. The purpose is to modify the ductility and cracking resistance of GFRP-reinforced beams, which are prone to early cracking and excessive deflections instigated by the low modulus of elasticity of GFRP. Six self-compacting concrete specimens (1500×240×200 mm), incorporating steel fibers of two lengths (25 mm and 40 mm) with varying distribution depths, were tested to assess their structural performance. The results indicate significant enhancements in cracking resistance, stiffness, energy absorption, ductility, and flexural strength. Tested beams reinforced with 40 mm-long steel fibers exhibited a 23.9%–24.2% development in the ultimate moment capacity associated with the steel-reinforced specimens, whereas those with 25 mm fibers showed smaller increases (2.7%–3.1%). The cracking resistance improved by up to 33.3% in beams with 40 mm-long fibers and by 16.67%–20% in those with 25 mm-long fibers, associated with a non-fibrous GFRP specimen. Additionally, the inclusion of 40 mm hooked-end steel fibers significantly enhanced ultimate deflection, with peak deflections increasing by 30.2%–44.8% compared to steel-reinforced beams. Fibrous GFRP-reinforced beams exhibited up to 154% higher energy absorption under ultimate load than a non-fibrous GFRP beam. All fibrous GFRP-reinforced beams achieved deformation-based ductility indices between 4.2 and 6.9, exceeding the minimum threshold of 4 for adequate deformability. These findings confirm that incorporating 40 mm steel fibers significantly improves the structural behavior of GFRP-reinforced concrete specimens, offering valuable insights for optimizing their design.
Enhancing Post-Fire Performance of Lightweight RC Slabs Using Expanded Polystyrene and Steel Fibers: An Experimental Study Abd, Alaa A.; Abbas, Rafaa M.
Civil Engineering Journal Vol. 11 No. 10 (2025): October
Publisher : Salehan Institute of Higher Education

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.28991/CEJ-2025-011-10-03

Abstract

Aggregate significantly influences the mechanical properties of concrete material and has a crucial role in post-fire behavior. This research focuses on investigating the post-fire behavior of a fiber-reinforced one-way slab made from lightweight expanded polystyrene (EPS) aggregate concrete. The experimental study consisted of testing fourteen fiber-reinforced self-compacting concrete (SCC) one-way slabs with EPS as a partial replacement of coarse aggregate. All specimens have identical dimensions of 1800×500×125 mm. The main parameters investigated included fire exposure, EPS replacement ratio, and steel fiber content. The tested specimens were divided into two groups. The first group included seven specimens tested under monotonic static load, whereas the seven specimens of the second group were tested under monotonic static load after being exposed to a steady-state temperature of 700°C for one hour. Following exposure to fire, results revealed a dramatic decrease in the structural performance of the slab specimens, including cracking load, ultimate load, stiffness, absorbed energy, and ductility, especially for the non-fibrous lightweight samples. However, adding EPS beads in the concrete mixture helps in reducing strength degradation due to fire exposure, and the higher the EPS content, the less strength degradation. This result exposed the positive impact of EPS on the structural performance of RC lightweight slabs exposed to fire due to their thermal properties. Moreover, results revealed a significant enhancement in post-fire stiffness, ductility, and absorbed energy of the RC slab due to steel fiber inclusion, showing their constructive impact on the slab performance.
AI-Driven Shear Capacity Model of Steel Studs in Composite Structural Systems Hanoon, Ammar N.; Abdulhameed, Haider A.; Abdulhameed, Ali A.; Hason, Mahir M.; Abbas, Rafaa M.; Mansi, Aseel S.
Civil Engineering Journal Vol. 12 No. 2 (2026): February
Publisher : Salehan Institute of Higher Education

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.28991/CEJ-2026-012-02-04

Abstract

In composite steel-concrete structures, shear connectors in the form of headed steel studs are commonly utilized to transfer longitudinal shear force developed at the interface between the two materials. To overcome the shortcomings of design codes, which frequently understate shear capacity and fail to take advantage of sophisticated computational methods, this paper presents an optimization attempt to estimate the shear strength of headed steel studs utilizing the Grey Wolf Optimizer (GWO) technique using MATLAB software. Data from 234 experimental tests are employed to identify and highlight key input parameters influencing the shear strength of headed steel studs. These key parameters include concrete compressive strength (f’c), diameter (D), and tensile strength of the steel stud shank (fu). After identifying and examining the limits of the experimental data, the proposed model has been developed using about 80% of the mixed raw dataset. The remaining 20% of the raw data is utilized to validate the proposed model. The predicted shear strength of headed steel studs closely matched the experimental results. This research offers an innovative strategy to measure the steel stud's shear capacity employing GWO, showing the current code's limitations. The GWO model showed excellent accuracy in predicting the shear strength with an R-value of 0.9922, indicating that the predicted value is in good agreement with experimental observations. Interestingly, the model's mean absolute error with 100 wolves in the GWO method was only 7.51%, showing the proposed model provides an improvement in shear capacity forecasting for practical structural engineering applications.
Co-Authors Abd, Alaa A. Abdulhameed, Ali A. Abdulhameed, Haider A. Allawi, Abbas A. Hanoon, Ammar N. Hason, Mahir M. Mansi, Aseel S. Mohammed, Shatha D. Oukaili, Nazar K. Salman, Hamza M.