Hamed Salem

As sustainable construction and infrastructure durability become critical priorities, understanding the coupled influence of reinforcement corrosion and recycled concrete aggregate (RCA) is essential. This study develops three-dimensional finite element models in ABAQUS to simulate the flexural response of reinforced concrete (RC) beams with RCA replacement ratios ranging from 0 to 100% and reinforcement corrosion mass-loss levels of 0–20%. Corrosion effects were represented through corrosion-dependent degradation of steel mechanical properties and bond behavior, together with strength reduction in the corrosion-cracked concrete cover. The numerical framework was validated against published experimental beam tests, showing good agreement in load–deflection response and damage distribution within the tension zone corresponding to the observed cracking regions, with ultimate-load differences generally within 7%. A parametric investigation was conducted to quantify the reduction in ultimate capacity under combined deterioration mechanisms. For natural-aggregate beams, peak-load reduction increased from approximately 8–12% at 5–7% corrosion to about 18–22% at 10% corrosion, reaching nearly 30–35% at 20% corrosion. Increasing RCA content reduced the baseline capacity and amplified corrosion sensitivity, with higher replacement ratios showing larger peak-load losses at moderate-to-severe corrosion levels. Ultra-high performance concrete (UHPC) bottom-layer strengthening was also evaluated as a mitigation strategy. In this approach, UHPC was used only as a thin localized layer at the tension zone, resulting in a limited material volume while extending the service life of RCA-based RC beams. A 20 mm UHPC layer typically restored the ultimate load to within ± 5% of the corresponding un-corroded control beam (for corrosion levels up to about 10%), while 40 mm and 60 mm layers increased the ultimate load to approximately 8–18% and 15–25% above the corresponding control response, respectively. Finally, a modified cracking moment equation based on the American Concrete Institute (ACI) formulation was proposed to account for the combined influence of reinforcement corrosion and recycled aggregate content for the investigated beam configuration.

This study investigates the influence of graphene nanoplatelets (GnP) on the mechanical properties of concrete and the flexural behavior of reinforced concrete beams (GnP RC beams). Concrete mixtures were prepared with GnP concentrations of 0.00%, 0.02%, 0.04%, 0.10%, and 0.30% by cement weight. Key mechanical properties evaluated include compressive strength, splitting tensile strength, flexural strength, shear capacity, and modulus of elasticity. Additionally, the flexural and shear behavior of GnP-RC beams was analyzed, focusing on the moment–curvature relationship, ductility, crack patterns, and failure mechanisms. The incorporation of GnP aimed to enhance concrete’s mechanical performance and structural efficiency through nanoscale reinforcement. The results demonstrated that GnP significantly improved the mechanical properties of concrete. At 0.04% GnP, compressive strength increased by 12%, and splitting tensile strength improved by 18.6%. The ultimate flexural and shear capacities of GnP-RC beams increased by 20.7% and 40.8%, respectively, whereas post-cracking Ductility improved by 53%. A noticeable refinement in crack distribution was observed, indicating improved stress transfer and reduced crack widths. Moreover, the inclusion of GnP enhanced the overall stiffness of the beams, contributing to their improved load-carrying capacity. These findings highlight the potential of GnP to address key limitations of conventional concrete, offering a promising approach for more sustainable and high-performance construction materials.

Corrosion due to insufficient grout filling can result in a sudden fracture of PC steel tendons. When a vertically tightened PC tendon in PC girders is ruptured, all the accumulated strain energy is suddenly released. The ruptured PC bar will severely damage cover concrete and asphalt pavement, and PC bars may protrude out of the structure, which may cause severe accidents. In the current study, the effects of 15 mm cover concrete and two-layered asphalt pavement system on preventing protrusion of PC bars were investigated. Numerical simulation of rupture and protrusion of PC bars were studied using the Applied Element Method. The numerical simulations were verified based on the experimental results. In the process of verification, many influential parameters, such as the effects of contact stiffness between elements, fracture energy of concrete, mesh sensitivity, time interval sensitivity, material properties, and strain rate effect, were investigated. This study found that AEM numerical simulation with appropriate modeling showed good agreement with the experimental results, which exhibited the effectiveness of the asphalt pavement system with appropriate material and thickness preventing protrusion of the PC bar tendon.

Exterior columns are highly susceptible to structural damage in cases of blast attacks, and its failure may lead to a progressive collapse of the entire structure. In this study, a three‐dimensional nonlinear dynamic analysis was carried out on a 10‐Storey reinforced concrete office building. The building was designed according to ACI 318, then its exterior columns were subjected to blast loading threat. The computational program used is Extreme Loading for Structures software, which is based on the applied element method (AEM). The AEM can estimate the structural behavior from the elastic stage through cracking, large displacement, complete elements separation, and eventually collapse. In this study, an exterior column is analyzed under different weights of (TNT) detonation charges concerning different standoff distances, the behavior of the columns is evaluated according to UFC 3‐340‐02 and PDC‐TR 06‐08. Analysis trials are carried out to estimate a safe and economical column design that can withstand a predefined charge weight and standoff distance.

Unreinforced load-bearing masonry (URM) buildings represent a significant portion of the non-engineered old buildings in many developing countries aiming to reduce the construction cost. The walls of those buildings are developed to resist gravity loads. Lateral loads induced by earthquakes or wind may cause severe their damage. In the current study, a numerical investigation is carried out for a seismic assessment of a typical four-story, load-bearing building in Giza, Egypt. The full 3D nonlinear dynamic analysis is carried out using the Applied Element Method (AEM), which proved to be efficient in such case where partial or total collapse is expected. The study includes two earthquake zones in Egypt called zone (3) and zone (5B), which are the actual studied building seismic zone and the highest seismic activity zone in Egypt, respectively. Carbon fiber reinforced polymers (CFRP) laminates with different thicknesses and different configurations are used in strengthening unreinforced masonry walls to study the efficiency of the proposed rehabilitation technique on a realistic structure.

A three dimensional nonlinear dynamic analysis is performed for a single well observation platform. The structure consists of a single level service deck supported by three driven piles and a bracing frame. Extreme Loading for Structures (ELS) software was used. The analyses are carried out under the effects of impact for a 3500 ton vessel moving at speeds varying between 1 and 10 knots. The effect of soil type was investigated. The effect accidental failure of a supporting pile was studied and the possibility of progressive collapse of the platform was evaluated. The study found that there is a difference of up to 20% in the results using nonlinear dynamic when compared to the traditional equivalent static analysis. The analysis show that the soil type significantly affects the internal forces in the platform as well as the total platform displacement.