Hany Ahmed Abdalla

This study investigated the shear behavior of large-scale reinforced concrete (RC) columns strengthened with either Engineered Cementitious Composite (ECC) or Ferro-Engineered Cementitious Composite (Ferro-ECC) jackets, with the latter incorporating expanded steel wire mesh (ESWM), thereby distinguishing the contribution of the ECC jacket from the additional contribution of ESWM. Ten large-scale specimens were tested without axial compression under monotonic four-point loading to evaluate the effects of mesh type, number of mesh layers, and transverse reinforcement under two deficiency scenarios: excessive stirrup spacing (250 mm) and complete absence of stirrups. Structural performance was assessed in terms of load–deflection response, cracking behavior, failure mode, stiffness, deformability, energy absorption, and shear capacity. The experimental cracking moments and ultimate shear capacities were evaluated against widely used design codes, and modified prediction models were proposed to account for the contributions of ECC and ESWM strengthening. The results showed that ECC strengthening alone significantly enhanced the shear performance of both stirruped and unstirruped RC columns, increasing the ultimate load by approximately 92–118% relative to the corresponding control specimens. The use of hybrid ECC–ferrocement jackets further increased the ultimate load by 106–123% with a single mesh layer, while two mesh layers resulted in increases of up to 164% and 244% for the stirruped and unstirruped columns, respectively. Strengthening delayed the initiation of flexural and diagonal cracking, increased crack distribution, and maintained service-load crack widths within acceptable limits (≈0.10–0.30 mm). Initial stiffness increased by up to 136%, deformation capacity improved by 25–60%, and energy absorption increased by 121–240% for ECC alone and up to 6.21 times with ECC–mesh systems. Coarse mesh was more effective in single-layer configurations, whereas fine mesh provided superior performance in double-layer systems through enhanced crack control. The proposed cracking and shear prediction models showed good agreement with the experimental results.

This study investigates the shear performance of reinforced concrete (RC) beams strengthened with near-surface-mounted (NSM) carbon fiber-reinforced polymer (CFRP) ropes under ambient and elevated temperature conditions. An experimental program comprising twelve RC beams was conducted, including both normal- and high-strength concrete specimens. The beams were strengthened using CFRP ropes installed at two orientations (45° and 90°) and two spacing configurations (150 mm and 200 mm). Ten specimens were exposed to a temperature of 600 °C prior to shear testing. The experimental results were evaluated against finite element (FE) simulations and shear strength predictions obtained from ACI 440.2R provisions. The FE models demonstrated close agreement with the observed experimental response, whereas ACI 440.2R consistently yielded conservative shear strength estimates, particularly for high-strength concrete beams. The results confirm that inclined CFRP configurations and reduced rope spacing significantly enhance shear capacity, even after severe thermal exposure, with measured strength gains reaching approximately 75% relative to unheated control beams and up to 135% compared to heated control specimen. The findings emphasize the sensitivity of NSM CFRP in terms of strengthening effectiveness to elevated temperature and highlight the limitations of existing design provisions when applied to fire-damaged RC members.

Hidden beams in reinforced concrete (RC) structures are widely used to meet architectural requirements; however, their reduced effective depth limits shear capacity. This study investigates the shear behavior of hidden beams reinforced with innovative rectangular staggered continuous spiral stirrups, addressing the absence of design guidelines for such reinforcement systems. Nine one-eighth-scale continuous beams were tested under two-point loading, with mortar used to reduce scale effects. The influence of the number, geometry, and configuration of spiral reinforcement was investigated. Both conventional and spiral stirrups significantly improved shear performance compared to the reference beam without transverse reinforcement (HB9-No). Beams with normal stirrups (HB1-N20, HB2-N30, HB3-N40, HB4-N50) increased shear capacity by 115%, 82%, 23%, and 4%, while spiral stirrup beams (HB1-S20, HB2-S30, HB3-S40, HB4-S50) achieved corresponding increases of 174%, 144%, 73%, and 27%, respectively. Overall, spiral reinforcement enhanced shear capacity and energy dissipation by approximately 30% and 46%, respectively, compared with conventional stirrups. Prototype capacities estimated using scaling relationships were compared with international design codes, which were found to be conservative. The findings demonstrate the effectiveness of spiral stirrups in improving shear strength and ductility and emphasize the need to include their contribution in future shear design equations for hidden beams.

Strengthening post‐tensioned (PT) slabs is essential for enhancing their load‐carrying capacity and overall structural performance in a wide range of practical applications. This study investigates the effectiveness of two strengthening techniques—external reinforced concrete (RC) jacketing and carbon fiber‐reinforced polymer (CFRP) reinforcement—through both experimental testing and numerical modeling. Five one‐way PT slabs were fabricated and tested under four‐point bending, comprising one control specimen and two specimens for each strengthening method. The effects of varying the reinforcement mesh configuration in the RC jacket and the number of CFRP layers were examined. Key performance indicators, including crack patterns, midspan deflection, and ultimate load capacity, were recorded during testing. Experimental failure loads were compared with predictions from international design codes. The results indicated that PT slabs strengthened with RC jacketing exhibited load capacities exceeding those predicted by AS 3600, ACI 318, and Eurocode 2 by 2.7%–19.7%, while CFRP‐strengthened slabs showed improvements ranging from 6.9% to 12.9%. A robust finite element model (FEM) was developed and validated against the experimental data, incorporating the nonlinear behavior of concrete, steel reinforcement, prestressing tendons, and CFRP. A comprehensive parametric study, involving 54 numerical simulations, was conducted to evaluate the influence of critical parameters on the load capacity of strengthened slabs. The results demonstrated that increasing the yield strength and diameter of the jacketing reinforcement, as well as the compressive strength of the jacketing concrete, significantly enhanced load capacity. Furthermore, increasing the number of CFRP strips improved the performance of strengthened slabs by 3.4%–18.9%.

A 3D finite element model (FEM) for predicting the distribution of lateral pressure in a square flexible walled steel silo during the filling phase was analyzed in this study. The numerical approach, developed using Abaqus software, predicts the stress state in bulk solids, as well as the pressures exerted on the silo walls. An elasto-plastic model using the Drucker–Prager criterion was employed to simulate the behavior of the granular materials. The FEM simulates the behavior of the bulk solid and its interaction with the silo’s wall and base using a surface-to-surface discretization model. The model’s predictions were validated by previous experimental measurements. The results revealed good agreement between the FEM predictions and the experimental measurements. The research confirms that the lateral pressure distribution is not uniform at any silo level. This highlights the fact that many available theories and current design codes are not accurate for flexible steel walls. As a result of the wall’s deformability, pressure regimes on the silo wall change significantly in the horizontal direction at any level. The results showed that the horizontal variations of lateral pressure change drastically with regard to wall stiffness. The FEM has been used to investigate the effect of critical parameters on wall pressure distribution, such as properties of bulk solids, wall thickness, and silo type, whether deep or flat.

Cable-stayed bridges have gained greater coverage in the last few decades. This study focuses mainly on two parameters. Firstly, the shape of pylons; the performance of many shapes is investigated after being exposed to an earthquake. Secondly, the effect of changing deck width of an inverted Y-shaped pylon with variation in main span length. The numerical study was performed using MIDAS civil software. It was concluded that the most efficient pylon shape in terms of seismic performance was that of pyramid shape followed by a delta shape. In addition, it was found that changing deck width for the same main span gives a negligible difference to normalized shear force.

Using recycled aggregate in the construction of reinforced concrete (RC) buildings has become essential to reduce the waste produced from demolished buildings. In this paper, the influence of using carbon fiber reinforced polymer (CFRP) in strengthening of RC beams with recycled coarse aggregate (RCA), as a partial/full replacement for natural coarse aggregate (NCA), was experimentally investigated. Twelve RC beams with various RCA ratios (0%, 30%, 70%, and 100%) were prepared and tested under four-point loading. Four beams without CFRP were tested till failure while the other eight beams were subjected to service loads then strengthened using CFRP and re-tested till failure. The cracking pattern, deflection, as well as strain in longitudinal and transversal reinforcement were recorded. The failure loads of the tested beams were compared to those predicted from various international design codes. Results showed that the flexural cracks appeared in specimens with 100% RCA earlier than those with NCA. Moreover, the increase in RCA% resulted in resisting tensile stresses by stirrups at a lower load value and achieving a more ductile behavior. Also, the experimental results showed that including RCA in beams slightly decreased the failure load for both strengthened and un-strengthened RC beams. Furthermore, beams with higher amount of RCA experienced more deflections than those with lower amount of RCA. Such behavior was found more prominent in the CFRP strengthened beams.