This study investigates the structural behavior of composite double-web steel beams filled with different types of concrete made from a combination of recycled concrete aggregates and normal aggregates. The research includes both experimental and numerical analyses. Seven specimens were tested under symmetrical two-point loading, all having identical geometric properties: a span length of 1100 mm, flange plates 120 mm wide and 6 mm thick, and web plates 3 mm thick and 188 mm deep. The specimens were divided into two groups, with a control beam without concrete infill. Group one included beams filled with normal concrete in different locations (middle region, two sides, and fully filled), while group two mirrored the same fill locations but used recycled concrete instead. The experimental results showed that using normal concrete improved the ultimate load by 10.19% to 55.30%, with the fully filled beam achieving a maximum increase in ductility of about 568% and a stiffness improvement ranging from 2.6% to 39% compared to the control beam. Beams filled with recycled concrete showed increases in ultimate load from 9.52% to 42.03%, ductility improvements of up to 380%, and stiffness enhancements between 4.5% and 8.03%. Numerical modeling using ABAQUS (2021) showed excellent agreement with the experimental results, with differences in ultimate load and maximum deflection averaging 5.5% and 7.9%, respectively.

This study tests steel double web sections filled with normal concrete. All beams have the same length span, cross-section (I-section), load type, and boundary

Concrete remains the most widely used construction material worldwide due to its inherent strength and durability. However, the industry’s heavy reliance on natural resources has prompted increasing interest in sustainable alternatives. This study explores the use of recycled and lightweight materials specifically crushed bricks, crushed lightweight concrete, and lightweight expanded clay (Leca) as substitutes for natural coarse aggregates in the production of lightweight concrete. In addition, a comparative analysis was conducted between concrete mixes with and without steel fibers to evaluate the impact of fiber reinforcement on overall performance. Experimental results revealed Modifications in HGS led to a notable increase in cube compressive strength (by about +19% when compared to HG), while HRCS showed the greatest increase in cylinder compressive strength (by about +32%). In comparison to HG, HLS also demonstrated an improvement in cylinder strength. However, compared to the reference mix, HL and HB showed reduced compressive strength. Both HB and HL achieved significant unit weight reductions when compared to the reference mix HG. In particular, HB showed a density decrease of about 15%, whereas HL showed a more noticeable reduction of almost 20%. According to these results, HL and HB offer the biggest improvements in weight efficiency.

This study presents a numerical simulation of the behaviours of compact steel arch beams, with and without openings, using the commercial finite element software ABAQUS. Numerical model was firstly validated against under-publishing research to verify the accuracy of FEA results and then used to conduct a parametric study to investigate the effects of several parameters on the load - deflection curve of the arch steel beams with openings such as opening area, opening shape, openings number, yielding stress of steel material, radius of arch beam and effect of adding steel stiffeners. The results from the numerical investigation showed that the FEA results gave a good agreement with the experimental results in terms of ultimate strength, maximum deflection, load-deflection curves, and failure mode. The parametric study further showed that the ultimate failure loads for arch beams with openings decreased with the increase in the opening diameter from nearly 2 to 21% for openings of diameters 50mm and 125 mm, respectively, located at the centre of the web, while the ultimate load capacity of steel arch beams with edge openings decreased by about 26% in comparison with the control beam when the diameter increased to 125 mm. Also, the increase in the radius of the arch beam using radii of (537.3, 797.5, and ∞) mm resulted a decrease in ultimate load capacity about 17% and 40% for radii (797.5 and ∞ mm) respectively, compared with the control beam of radius 537.3 mm.

This research investigates the behavior of extended reinforced concrete beams that have been enhanced using CFRP at the extension points. Five reinforced concrete beams with measurements of 2500 mm in length, 150mm in width, and 260mm in height were built and extended in different types. The studied cases included varied CFRP strengthening schemes for the splice joints. The findings conclude that the inclusion of horizontal stirrups on the complete top of the beam produced comparable results to those of the reference beam. Additionally, the spliced beams glued at their lateral faces and strengthened by vertical CFRP laminates provided a marginal increase in their ultimate loads. The results also showed that the strengthening with carbon fibers exhibited lower crack width than the reference beam in general.

Despite the availability of numerous studies addressing the strengthening/rehabilitation of reinforced concrete columns using steel jacketing or the NSM technique, most previous works have focused on evaluating each technique individually or under different loading conditions and models, which limits the possibility of making a direct and fair comparison between these techniques. Therefore, the research gap lies in the need for a systematic study comparing steel jacketing and NSM with CFRP bars strengthening of reinforced concrete columns under the same geometric and material properties and a unified cyclic loading protocol, with a comprehensive evaluation of seismic performance indicators such as strength, ductility, stiffness degradation, and energy dissipation. The results shows that all rehabilitation methods greatly enhanced the tested columns’ structural performance in terms of stiffness, ductility, and lateral load capacity when compared to the control specimen. The Near Surface Mounting (NSM) technique and steel plate strengthening were successful in improving the load-carrying capacity and structural behavior under lateral loading. The NC-STJ4 achieved a higher increase in lateral load capacity (161%) compared with the NC-STJ2 (135%). Compared to the NC-NSM2 (173%), the NC-NSM4 produced a marginally higher improvement (184%). The NC-STJ4 exhibiting a marginally greater stiffness increase (160%) than the NC-STJ2 (156%).