Background: Fiber reinforced composite materials are becoming popular in civil engineering construction practices. One of the most practical applications of these materials is concerned with the strengthening and retrofitting of reinforced concrete compression members by means of external confinement with the GFRP sheets. The role of FRP for strengthening of existing or new reinforced concrete structures is growing at an extremely rapid pace owing mainly to the ease and speed of construction, and the possibility of the application without disturbing the existing functionality of the structure. Objective: The ductility and strength behavior of reinforced concrete columns (Square & Circle) confined by glass and carbon Fiber Reinforced Polymer (FRP) sheets were experimentally investigated Methods: In the library, we tested and cast a total of fourteen column specimens. The tested specimens in this study were square and circle columns, the square specimens tested in this experimental study had dimensions of 135x135 mm cross-section while the circle specimens had 150 mm diameter. The columns were loaded at their supports and made prepared to avoid local failure at supports due to steel plates. Two types of fiber reinforcements sheets were used for strengthening the columns (Carbon and Glass fiber polymer sheets). To prevent the highly stressed slender longitudinal bars from buckling outward, adequate amounts of steel ties were utilized in the height of the columns. During the test of the columns, the central deflection and central fiber strains were measured using dia1 gauges and strain gauges Discussion: The CFRP strains progressed very slowly before the yielding of longitudinal reinforcement bars but quickly, eventually, due to the concrete expansion in the plastic hinge. The wrapped CFRP sheets contribute to both the shear strength and the confinement of concrete in column specimens. The results signify that the percentages of increase in the carrying load capacity due to strengthen, using carbon and glass FRP sheets, were greater in the circular columns compared with the square columns for all the types of confinements used in this study. The ductility factor increased by the strengthen column ranged between 1.35-2.78, while the greatest ductility factor obtained when the circular columns strengthen with glass FRP sheets fully wrapped. Conclusion: -The maximum ratio of increase in the carrying load capacity obtained when the column strengthens fully wrapped. - The columns (circular and square) strengthen with carbon FRP sheets, the greater carrying load capacity obtained when compared the columns strengthen with glass FRP sheets. -The percentages of increase in the carrying load capacity due to strengthen, using carbon and glass FRP sheets were greater in the circular columns compared with the square columns for all the types of confinements. - The stains developed in the confined circular columns are greater than stains in the confined square columns. -The ductility factor increased by the strengthen column, while the greatest ductility factor obtained when the circular columns strengthen with glass FRP sheets fully wrapped.

This study develops data-driven models for predicting the shear capacity of reinforced concrete (RC) beams longitudinally reinforced with fiber-reinforced polymer (FRP) bars and lacking transverse reinforcement. Owing to the comparatively low elastic modulus and linear–elastic–brittle behavior of FRP bars, reliable shear prediction remains a design challenge. A curated database of 402 tests was compiled from the literature, spanning wide ranges of beam size (width b, effective depth d), concrete compressive strength (f′c), FRP elastic modulus (Ef), longitudinal reinforcement ratio (ρf), and shear span-to-depth ratio (a/d). Multiple multivariate regression formulations—both linear and nonlinear—were developed using combinations of these variables, including a mechanics-informed reinforcement index (ρf·Ef). Model predictions were benchmarked against 15 existing expressions drawn from design codes, standards, and prior studies. Across the full database, the proposed models demonstrated consistently stronger agreement with experimental results than the existing predictors, yielding higher correlation and lower prediction error. The resulting closed-form equations are transparent and straightforward to implement, offering improved accuracy for the preliminary design and assessment of FRP-RC beams without stirrups while highlighting the influential roles of Ef, ρf, and a/d within the observed parameter ranges.

Erbil city essentially suffers from the risk of earthquakes generated by Zagros-Taurus Belt. The central objective of this study is to identify the seismic characteristics and required seismic parameters for structural analysis. The methodology concentrated on reviewing the seismology and geology of Erbil city. It was concluded that the tectonically classified by an outer platform of the low folded zone in the position of Western Zagros Fold-Thrust Belt of the Arabian plate, geologically covered by Quaternary sediments and lithologically described by fluvial sediments, and the dynamic soil properties classified by site Class D. Seismicity review indicated that the seismic source is characterized by strike-slip (normal) fault and majority events exhibit at the shallow crustal with expected moment magnitude between 6 and 7.5. It was observed that the peak ground acceleration (PGA) has been updated, especially after the last cyclic earthquake in the region. The summary of the previous seismic hazard indicates that the PGA according to the World Health Organization, Global Seismic Hazard Assessment Program, and Uniform building code is identified by the value higher than 0.3 g for 475 years return period, while according to national probabilistic seismic hazard analysis studies in Iraq and Arabian Peninsula is identified by 0.4 g for 2% probability of exceedance in 50 years (2475 years return period), and estimated PGA to be 0.25 g for 10% likelihood of exceedance in 50 years (475 years return period), in a term of 5% damped at bedrock condition. Proposed spectral acceleration (Sa) in Erbil city at 0.2 and 1.0 s evaluated to be 1.0 g and 0.53 g, for the site Class D and compared with Sa in the literature.

This study investigated the effectiveness of using near-surface mounted (NSM) steel bars to restore the shear strength of deep beams and deal with the presence of openings in slender beams. Fourteen simply supported reinforced concrete beams were tested with varying shear span-to-depth ratios (a/h) of 1.5 and 3.61, divided into two groups, and subjected to a two-point load configuration. Some beams had openings at different positions, classified as large or small with opening height ratios (ho/h) of 0.4 and 0.2, respectively. In the second group, six specimens were reinforced with NSM steel bars in three stirrup configurations (square, diamond, and parallelogram) surrounding the openings. All specimens had a cross-section size of 100 mm × 150 mm and a total length of 2000 mm. The results of the test indicated that having openings in the beams led to reductions in ultimate load capacity for different beam types. Specimens reinforced with diamond stirrup bars showed an increase in ultimate load capacity of up to 33.1%, while those with square and parallelogram stirrup bars improved by up to 21.5% and 26.5%, respectively. Minor variations in bar diameter had slight effects on ultimate load capacity, resulting in a 10% increase for the parallelogram scheme and 7% for the square scheme. The reductions in ultimate load capacity due to openings were 45% for large circular openings in the shear zone of deep beams, 18.7% for large circular openings in slender beams subjected to shear, 14.6% for large circular openings affecting both shear and flexural behavior and 19.5% for small openings impacting shear and flexural behavior in slender beams.

This study investigates the synergistic influence of recycled concrete aggregate (RCA) and recycled steel fibers (RSF) on the fresh and hardened performance of eco-efficient fiber-reinforced self-compacting concrete (SCC). Twelve C30/37.5 mixtures were produced using demolition waste as coarse RCA at replacement levels of 25, 50, 75, and 100% by mass, combined with RSF recovered from scrap tires at volume fractions of 0.25, 0.50, and 0.75%. Fresh properties were assessed in accordance with EFNARC guidelines using slump-flow (T500), V-funnel, L-box, and J-ring tests, while hardened performance was evaluated through compressive, splitting tensile, and flexural strengths at 28 days, together with density and ultrasonic pulse velocity (UPV). Increasing RCA and RSF contents reduced workability, reflected in lower slump-flow diameters and higher T500 and V-funnel times, although most mixtures maintained satisfactory self-compacting behaviour. Compressive strength decreased with RCA content and, to a lesser extent, with higher RSF, with a maximum reduction of about 39% at 100% RCA relative to the control mix, yet values remained structurally acceptable. In contrast, RSF markedly enhanced tensile and flexural responses: at 25% RCA, 0.75% RSF increased splitting tensile and flexural strengths by approximately 41% and 29%, respectively, compared with the corresponding fiber-free mix. RCA reduced density and UPV by about 10–14%, but these reductions were partially mitigated by RSF addition. Overall, the results demonstrate that SCC with moderate RCA (25–50%) and RSF (0.50–0.75%) can achieve a favourable balance between rheological performance and enhanced tensile and flexural behaviour, offering a viable composite solution for sustainable structural applications.