Elastic bending of imperfect functionally graded sandwich plates (FGSPs) laying on the Winkler-Pasternak foundation and subjected to sinusoidal loads is analyzed. The analyses have been established using the quasi-3D sinusoidal shear deformation model. In this theory, the number of unknowns is condensed to only five unknowns using integral-undefined terms without requiring any correction shear factor. Moreover, the current constituent material properties of the middle layer is considered homogeneous and isotropic. But those of the top and bottom face sheets of the graded porous sandwich plate (FGSP) are supposed to vary regularly and continuously in the direction of thickness according to the trigonometric volume fraction's model. The corresponding equilibrium equations of FGSPs with simply supported edges are derived via the static version of the Hamilton's principle. The differential equations of the system are resolved via Navier's method for various schemes of FGSPs. The current study examine the impact of the material index, porosity, side-to-thickness ratio, aspect ratio, and the Winkler-Pasternak foundation on the displacements, axial and shear stresses of the sandwich structure.

Organic solar cells utilized natural polymers to convert solar energy to electricity. The demands for green energy production and less disposal of toxic materials make them one of the interesting candidates for replacing conventional solar cells. However, the different aspects of their properties including mechanical strength and stability are not well recognized. Therefore, in the present study, we aim to explore the chaotic responses of these organic solar cells. In doing so, a specific type of organic solar cell constructed from layers of material with different thicknesses is considered to obtain vibrational and chaotic responses under different boundaries and initial conditions. A square plate structure is examined with first-order shear deformation theory to acquire the displacement field in the laminated structure. The bounding between different layers is considered to be perfect with no sliding and separation. On the other hand, nonlocal elasticity theory is engaged in incorporating the structural effects of the organic material into calculations. Hamilton's principle is adopted to obtain governing equations with regard to boundary conditions and mechanical loadings. The extracted equations of motion were solved using the perturbation method and differential quadrature approach. The results demonstrated the significant effect of relative glass layer thickness on the chaotic behavior of the structure with higher relative thickness leading to less chaotic responses. Moreover, a comprehensive parameter study is presented to examine the effects of nonlocality and relative thicknesses on the natural frequency of square organic solar cell structure.

This research presents a multi-material topology optimization for functionally graded material (FGM) and nonFGM with elastic buckling criteria. The elastic buckling based multi-material topology optimization of functionally graded steels (FGSs) uses a Jacobi scheme and a Method of Moving Asymptotes (MMA) as an expansion to revise the design variables shown first. Moreover, mathematical expressions for modified interpolation materials in the buckling framework are also described in detail. A Solid Isotropic Material with Penalization (SIMP) as well as a modified penalizing material model is utilized. Based on this investigation on the buckling constraint with homogenization material properties, this method for determining optimal shape is presented under buckling constraint parameters with non-homogenization material properties. For optimal problems, minimizing structural compliance like as an objective function is related to a given material volume and a buckling load factor. In this study, conflicts between structural stiffness and stability which cause an unfavorable effect on the performance of existing optimization procedures are reduced. A few structural design features illustrate the effectiveness and adjustability of an approach and provide some ideas for further expansions.

Man-made structure materials like concrete usually contain inclusions. These inclusions affect the mechanical properties of concrete. In this investigation, the influence of inclusion length and inclination angle on three-dimensional failure mechanism of concrete under uniaxial compression were performed using experimental test and numerical simulation. Approach of acoustic emission were jointly used to analyze the damage and fracture process. Besides, by combining the stress-strain behavior, quantitative determination of the thresholds of crack stress were done. concrete specimens with dimensions of 120 mm × 150 mm × 100 mm were provided. One and two holes filled by gypsum are incorporated in concrete samples. To build the inclusion, firstly cylinder steel tube was pre-inserting into the concrete and removing them after the initial hardening of the specimen. Secondly, the gypsum was poured into the holes. Tensile strengths of concrete and gypsum were 2.45 MPa and 1.5 MPa, respectively. The angle bertween inclusions and axial loadind ary from 0 to 90 with increases of 30. The length of inclusion vary from 25 mm to 100 mm with increases of 25 mm. Diameter of the hole was 20 mm. Entirely 20 various models were examined under uniaxial test. Simultaneous with experimental tests, numerical simulation (Particle flow code in two dimension) were carried out on the numerical models containing the inclusions. The numerical model were calibrated firstly by experimental outputs and then failure behavior of models containing inclusions have been investigated. The angle bertween inclusions and axial loadind vary from 0 to 90 with increases of 15. The length of inclusion vary from 25 mm to 100 mm with increases of 25 mm. Entirely 32 various models were examined under uniaxial test. Loading rate was 0.05 mm/sec. The results indicated that when inclusion has occupied 100% of sample thickness, two tensile cracks originated from boundaries of sample and spread parallel to the loading direction until being integrated together. When inclusion has occupied 75% of sample thickness, four tensile cracks originated from boundaries of sample and spread parallel to the loading direction until being integrated together. When inclusions have occupied 50% and 25% of sample thickness, four tensile cracks originated from boundaries of sample and spread parallel to the loading direction until being integrated together. Also the inclusion was failed by one tensile crack. The compressive strength of samples decease with the decreases of the inclusions length, and inclusion angle had some effects on that. Failure of concrete is mostly due to the tensile crack. The behavior of crack, was affected by the inclusion length and inclusion number.

The novel composite cold-formed steel (CFS)/engineered cementitious composites (ECC) beams have been recently presented. The new composite section exhibited superior structural performance as a flexural member, benefiting from the lightweight thin-walled CFS sections with improved buckling and torsional properties due to the restraints provided by thinlayered ECC. This paper investigated the shear performance of the new composite CFS/ECC section. Twenty-eight simply supported beams, with a shear span-to-depth ratio of 1.0, were assembled back-to-back and tested under a 3-point loading scheme. Bare CFS, composite CFS/ECC utilising ECC with Polyethylene fibres (PE-ECC), composite CFS/MOR, and CFS/HSC utilising high-strength mortar (MOR) and high-strength concrete (HSC) as replacements for PE-ECC were compared. Different failure modes were observed in tests: shear buckling modes in bare CFS sections, contact shear buckling modes in composite CFS/MOR and CFS/HSC sections, and shear yielding or block shear rupture in composite CFS/ECC sections. As a result, composite CFS/ECC sections showed up to 96.0% improvement in shear capacities over bare CFS, 28.0% improvement over composite CFS/MOR and 13.0% over composite CFS/HSC sections, although MOR and HSC were with higher compressive strength than PE-ECC. Finally, shear strength prediction formulae are proposed for the new composite sections after considering the contributions from the CFS and ECC components.

This paper examines a high-speed railway CRTS-II ballastless track-bridge system. Using the stationary potential energy theory, the mapping analytical solution between the bridge deformation and the rail vertical geometric irregularity was derived. A theoretical model (TM) considering the nonlinear stiffness of interlayer components was also proposed. By comparing with finite element model results and the measured field data, the accuracy of the TM was verified. Based on the TM, the effect of bridge deformation amplitude, girder end cantilever length, and interlayer nonlinear stiffness (fastener, cement asphalt mortar layer (CA mortar layer), extruded sheet, etc.) on the rail vertical geometric irregularity were analyzed. Results show that the rail vertical deformation extremum increases with increasing bridge deformation amplitude. The girder end cantilever length has a certain influence on the rail vertical geometric irregularity. The fastener and CA mortar layer have basically the same influence on the rail deformation amplitude. The extruded sheet and shear groove influence the rail geometric irregularity significantly, and the influence is basically the same. The influence of the shear rebar and lateral block on the rail vertical geometric irregularity could be negligible.

A new intelligent adaptive control scheme was proposed that combines observer disturbance-based adaptive control and fuzzy adaptive control for a composite structure with a mass-adjustable damper. The most important advantage is that the control structures do not need to know the uncertainty limits and the interference effect is eliminated. Three adjustable parameters in LMI are used to control the gain of the 2D fuzzy control. Binary performance indices with weighted matrices are constructed to separately evaluate validation and training performance using the revalidation learning function. Determining the appropriate weight matrix balances control and learning efficiency and prevents large gains in control. It is proved that the stability of the control system can be ensured by a linear matrix theory of equality based on Lyapunov's theory. Simulation results show that the multilevel simulation approach combines accuracy with high computational efficiency. The M-TMD system, by slightly reducing critical joint load amplitudes, can significantly improve the overall response of an uncontrolled structure.

The present study experimentally and analytically investigates the effect of tensile reinforcement ratio and arrangement on the behavior of FRP strengthened reinforced concrete (RC) beams. The experimental part of the program was comprised of 8 RC beams that were tested under four-point bending. Results have shown that by keeping the total cross-section area of tensile reinforcing bars constant, in specimens with a low reinforcement ratio, increasing the number and decreasing the diameter of bars in the section lead to 21% and 29% increase in the load-carrying capacity of specimens made with normal and high compressive strength, respectively. In specimens with high reinforcement ratio, a different behavior was observed. Furthermore, the accuracy of the existing code provisions and analytical models in predicting the load-carrying capacity of the FRP strengthened beams failed by premature debonding mode were evaluated. Herein, a model is proposed which considers the tensile reinforcement ratio (as opposed to code provisions) to achieve more accurate results for calculating the load carrying capacity of FRP strengthened RC beams.

Based on the third-order shear deformation theory, the wave propagations in doubly curved spherical- and cylindrical- panels reinforced by carbon nanotubes (CNTs) are firstly investigated in present work. The coupled equations of wave propagation for the carbon nanotubes reinforced composite (CNTRC) doubly curved panels are established. Then, combined with the harmonic balance method, the eigenvalue technique is adopted to simulate the velocity-wave number curves of the CNTRC doubly curved panels. In the end, numerical results are showed to discuss the effects of the impact of key parameters including the volume fraction, different shell types (including spherical (R₁=R₂=R) and cylindrical (R₁=R, R₂=→∞)), wave number as well as modal number on the sensitivity of elastic waves propagating in CNTRC doubly curved shells.

In this paper, static and dynamic bending of nanocomposite micro beam armed with CNTs considering agglomeration effect is studied. The structural damping is considered by Kelvin-Voigt model. The agglomeration effects are assumed using Mori-Tanaka model. The micro beam is modeled by third order shear deformation theory (TSDT). The motion equations are derived by principle of Hamilton's and energy method assuming size effects on the basis of Eringen theory. Using differential quadrature method (DQM) and Newmark method, the static and dynamic deflections of the structure are obtained. The effects of agglomeration and CNTs volume percent, damping of structure, nonlocal parameter, length and thickness of micro-beam are presented on the static and dynamic deflections of the nanocomposite structure. Results show that with increasing CNTs volume percent, the static and dynamic deflections are decreased. In addition, enhancing the nonlocal parameter yields to higher static and dynamic deflections.