In order to analyze the bending behavior of functionally graded carbon nanotubes (CNT)/fiber-reinforced composite laminated shells, an analytical solution based on the Galerkin technique is proposed. The mathematical formulations are generated based on higher-order shear deformation theory. Various geometrical schemes of shells are analyzed. Three distribution patterns of fibers are examined, FG-X, FG-O and FG-V, in addition to the uniform distribution (UD). The CNTs volume fraction is constant and evenly distributed throughout all shell layers. The virtual work principle is employed to derive the equilibrium equations. The influence of CNTs and fibers proportion, fibers distribution patterns, geometrical parameters and various boundary conditions on the deflection of CNTs/F-RC shells is investigated in detail.

Over the past few years, there has been an increasing emphasis on assessing structures in harsh environments to guarantee their safety and longevity. Nevertheless, precisely modeling the behavior of corroded elements and estimating their capability is still a major hurdle. Current models often depend on oversimplified assumptions, such as the uniform distribution of corrosion in steel bars, which can result in inaccurate forecasts of structural behavior. Through numerical and experimental studies, this research attempts to integrate recent findings on the corrosion distribution of steel bars with structural element modeling by introducing a modified beam-column element in OpenSees. For this purpose, different stochastic distributions of corrosion associated with steel bar area reduction were incorporated into the element by modified fiber modeling formulation. This study also considered the impact of transverse bars on element modeling, which further increased the results' accuracy. The accuracy of the proposed element was evaluated by comparing the modeling results with laboratory observations. The results indicated that the proposed element with suggested area reduction models considerably increases the modeling accuracy compared to the existing techniques based on even corrosion distribution.

This research paper deals with the analysis of buckling and free vibration of cross-ply laminated composite plates on elastic foundations. A refined plate theory based on the undetermined integrals terms is presented, which leads to reducing the unknown number to four instead of five or more unknowns used in the other theories. In the current theory, a function of shear with a hyperbolic form is employed, so the parabolic transverse shear stresses variation through the plate's thickness is obtained, and the zero shear stress conditions at the plate's top and bottom surfaces are satisfied. Therefore, the present formulation does not need shear correction factors. Pasternak elastic foundation mathematical model is considered in the formulation. The motion equations are determined using the virtual work principle, and the Navier approach is utilized to obtain the closed form solutions of cross-ply laminated plates. The fundamental frequencies and buckling loads are predicted by determining the eigenvalue problem. The present results are discussed and validated with results predicted using other previously published models.

This study focuses on enhancing concrete's mechanical strength and reducing its environmental impact through the integration of carbon fiber (CF) into Self-Compacting Concrete (SCC). Experimental trials included varying CF weights (0.2%, 0.4%, 0.6%, 0.8%, and 1.0%), assessing fresh and hardened concrete properties, and evaluating durability factors such as Acid Attack and Water Absorption, along with embodied carbon. Incorporating CF mitigates sagging and improves durability over time. Optimal improvements were observed with 0.6% CF, resulting in a significant 20.21% increase in compressive strength and a notable 58.38% enhancement in split tensile strength. Using Response Surface Methodology (RSM), a model was developed to optimize CF integration. Carbon fiber improves concrete by reinforcing the matrix, reducing micro-cracks, enhancing strength, and preventing segregation. In hardened concrete, it acts as secondary reinforcement, increasing strength and durability by reducing permeability. This lowers water absorption and improves resistance to acid attacks. Additionally, it reduces embodied carbon, lessening environmental impact while maintaining structural integrity. This study enhances our understanding of carbon fiber's benefits in concrete, guiding future development.

At present, the dynamics research of beams is mostly limited to free vibration and forced vibration, and the research on nonlinear transient response is little, and no one has studied the nonlinear transient response of beams with initial geometric imperfection under pulse loads. Based on this fact, the transient response characteristics of graphene platelet reinforced metal foams (GPLRMF) beams with initial geometric defects are discussed for the first time in this paper. Firstly, three kinds of graphene platelet (GPL) distribution patterns and foam metal porosity distribution patterns were considered, and the material properties were calculated by means of micromechanical models and mixture diffusion rules, and then, considering initial geometric defects, a dynamic model was established based on Euler-Bernoulli beam theory and von-Kármán nonlinear theory. Then, based on the Hamilton principle, the motion equation of the GPLRMF beam is derived. Finally, the corresponding transient response curve is obtained using the fourth-order Runge-Kutta method. In the study, the convergence of the model is verified to ensure the rationality and accuracy of the analysis results. In addition, a detailed study is conducted, including the distribution patterns and coefficients of porosity, the dispersion and weight fraction of GPLs, pulse load parameters, initial geometric imperfections and damping coefficient.

Nonlinear forced vibration analysisof a sandwich beam is investigated using the higher-order shear deformation theories (HSDT's). The sandwich beam is consists of viscoelastic core insert between two Functionally Graded Material layers. Viscoelastic properties are considered according to the Kelvin-Voigt viscoelastic model for isotropic materials. In the analysis, both normal and shear deformations are considered in the core by using the higher-order zig-zag theories. The method of multiple scales is coupled with a one mode Galerkin's procedure for a simply supported beam to achieve analytical frequency amplitude relationships for superharmonic resonance. Parametric study is conducted by considering various geometrical and material parameters, employing HSDT's and first-order deformation theory. The results reveal the effect of the slenderness of the sandwich beams on the hardening changes. In the other hand the results demonstrate the importance of the generic parameter "n" to reduce as far as possible the amplitude responses of the sandwich structures in superharmonic vibration case.

Latex modified concrete (LMC) possesses improved cracking strength and higher durability characteristics than concrete without latex. LMC overlays are typically used to increase the service life of bridge decks. On the other hand, the increasing use of high-performance concrete (HPC) in bridge deck slabs might affect the performance of LMC overlays due to the considerable difference between LMC and HPC characteristics. In this study, numerical analysis was performed using 2D linear Finite Element (FE) model coupled with Monte-Carlo simulation to examine the effect of the characteristics of the substrate, including differential shrinkage, overlay-to-substrate stiffness ratio, and cracking capacity on the probability of cracking (POC) and the probability of delamination (POD) of LMC bridge deck overlays. In addition, 3D nonlinear FE model was constructed to assess the effect of interface cracks on the structural response of bridge deck. It was found that high differential shrinkage strains and high stiffness differences between LMC and HPC can increase tensile stresses at the interface. The probability of cracking and delamination is governed by the tensile strength of the bridge deck substrate and crack development at the interface reduces the stiffness of bridge deck significantly.

Deterioration components (DCs) of reinforced concrete columns are important for the seismic performance assessment of reinforced concrete (RC) structures. DCs in RC columns includes: plastic chord rotation from yield to cap (Ɵ_p), post-capping plastic rotation capacity from the cap to point of zero strength (Ɵ_pc), and normalized energy dissipation capacity (λ). This paper investigates several machine learning (ML) algorithms for the prediction of DCs, referred to as ML-DCs, based on the results of 255 experimental tests conducted on reinforced concrete columns from 1973 to 2002. Also in this research, for the prediction of DCs, a learning-based prediction model is developed in a stacking ensemble framework, that is the training of several different basic models and their combination through the training of a meta-model to make a final prediction based on predictions made by the basic models. AdaBoost, Random Forest (RF), Support Vector Regression (SVR) and XGBoost algorithms are base learners. Among the ML algorithms, stacking ensembles showed the best results with a correlation coefficient (R²) of 0.778 for Ɵ_p, 0.703 for Ɵ_pc, and 0.809 for λ. The results of ML algorithms indicate that the ML models are more effective than the empirical relationships that are based on the experimental results.