Connections play a significant role on the seismic performance of structures subjected to gravity and lateral loads. One of the most important strategies for plastic hinge transfer is the strengthening of connections. Composite and welded connections are commonly used in steel bridges. Each of these connections can affect the structural response to lateral loads such as cyclic loads. In this study, four steel bridge models with different types of connections, including composite and welded connections, are created in the finite element (FE) platform ABAQUS. After validation of a FE model using available experimental data, cyclic loading has been employed according to the load history proposed by Scientific Advisory Committee (SAC). The results indicate that using composite connections can increase shear capacity and improve ductility of the system. Also using composite connection can transfer stress concentrated from connection to other areas.

The aim of the present study is to investigate a coupled arch dam-reservoir-massed foundation problem under two earthquake input mechanisms. The problem nonlinearity originates from opening/slipping of the vertical contraction joints of the dam body. The reservoir-structure interaction is taken into account assuming compressible reservoir. Also, the meshing approach (structured mesh vs. unstructured one) in the foundation medium is investigated. The Karoun-I double curvature arch dam is selected as a case study. Three components of the 1994 Northridge earthquake are selected as the free-field ground motion. A deconvolution analysis in 3D space is conducted to adjust the amplitude and frequency contents of the earthquake ground motion applied to the bottom of the massed foundation to determine the desired acceleration response at various points on the dam-foundation interface taking into account the coupling between the foundation and the structure. It is found that in the deconvolved earthquake input models, the maximum tensile and the compressive stresses increase by 19% and 12%, respectively in comparison with those of the free-field input models. In addition, modeling foundation using the unstructured mesh decreases the maximum compressive stresses within the dam body by about 20% in comparison with that obtained using the structured mesh model. In the same way, the maximum crest displacements in the horizontal direction decreases by about 30%.

This paper presents a careful theoretical investigation into interfacial shear stresses in steel beam strengthened with prestressed carbon/glass hybrid laminated plate. A closed-form rigorous solution for interfacial shear stress in steel beams strengthened with bonded prestressed carbon/glass hybrid laminated plates and subjected to a uniformly distributed load, is developed using linear elastic theory and including the variation in fiber volume fraction of carbon/glass hybrid laminated. The results show that there exists a high concentration of shear stress at the ends of the laminate, which might result in premature failure of the strengthening scheme at these locations. A parametric study has been conducted to investigate the sensitivity of interface behavior to parameters such as laminate and adhesive stiffness, the proportions and volume fraction of the fiber of carbon/glass hybrid laminated, the thickness of the laminate and the effect of prestressing where all were found to have a marked effect on the magnitude of maximum shear and normal stress in the composite member. This solution is intended for application to beams made of all kinds of materials bonded with a thin composite plate. This research is helpful for the understanding on mechanical behaviour of the interface and design of such structures.

This study aims to investigate the effect of cavity on electric energy harvesting from cantilever beam vibrations under electrostatic actuation. Electrostatic actuation is created by a layer of radioisotope materials that is placed on the opposite side of the beam emitting electrons. When the beam is charged, the electrostatic force is generated between the beam and the opposite plate and pulls the beam towards itself. After the beam strikes the radioisotope, it is electrically discharged and then released. The piezoelectric layer converts the released microbeam vibration into electricity. The equations of motion coupled with the electrical effects of the piezoelectric layer are extracted using Hamilton's principle and Gauss's law. The equations are discretized by Galerkin method. The exact mode shape of the cantilever beam with the piezoelectric layer is employed as the comparison function. By identifying the relations governing the system, the output voltage and consequently the amount of harvested electrical energy are obtained using various parameters such as thickness and position of the cavity and system electrical resistance. The results indicates that creating cavity has a significant effect on the energy harvesting.

A delamination analysis of a multilayered inhomogeneous beam structure under linear creep is developed. A viscoelastic model that consists of an arbitrary number of linear springs and linear dashpots is used. The cross-section of the beam is a circle. The beam is made of concentric longitudinal layers. Each layer is continuously inhomogeneous in thickness and length directions. Therefore, the shear moduli and the coefficients of viscosity of the viscoelastic model are distributed continuously along the thickness and length of each layer. Two concentric delamination cracks are located arbitrary between layers. The beam is loaded in torsion. Time-dependent solutions to the strain energy release rate for the two delaminations are derived by using the time-dependent strain energy in the beam. The strain energy release rates are derived also by the compliance method for verification. The variation of the strain energy release rate with time due to creep is evaluated. The effects of material inhomogeneity, external loading and delamination length on the strain energy release rate are investigated.

The paper is devoted to the study of thermomechanical interactions in a homogeneous nonlocal magneto-thermoelastic rotatingmediumunder the effect of hall current and two temperaturewithmemory dependent derivatives.Atwo-dimensionalmodel has been assumed. Laplace and Fourier transforms have been used to find the solution to the problemin transformed domain. The analytical expressions of components of displacement, stress and current density and conductive temperature are obtained in the transformed domain. Numerical inversion technique has been applied to obtain the results in the physical domain and the results are depicted graphically to show the effect of nonlocal parameter on the components of displacements, stresses, current density and conductive temperature. The effect of nonlocal parameter and hall current parameter has been represented graphically by taking different values.

The surface effect for a forced vibration of a double-nanobeam-system (DNS) coupled by a viscoelastic layer under a moving constant load is studied in this paper. The viscoelastic layer that couples the nanobeams to each other, is modelled as spring-damper system. The Euler- Bernoulli theory and a simply supported boundary condition are considered for both nanobeams. By using the analytical solution, the dynamic displacement is obtained by considering the surface elasticity and residual tension effect on each nanobeams. Furthermore, the several significant parameters such as the velocity of the moving load, spring constant, damping coefficient and also the surface effect have been studied using some plots and examples. Finally, by observing the diagrams it was concluded that as the length of the beams reduces, the surface effect has a considerable effect on each of nanobeams especially at Nano scale, where it was not achieved by classic theories.

The present article deals with a dynamic response analysis of a foam-based nanoscale plate based on finite strip method (FSM). The nanoscale plate formulation has been adopted based upon a higher order plate theory and then, a higher order finite strip has been used to solve the problem. The considered finite strip is capable of considering the bending displacement and also shear deformation effects. The foam-based material has been treated as a porous material with some particular pore distribution. The non-uniformity of strain field as well as the nonlocality of stress field have been incorporated with the usage of nonlocal strain gradient elasticity. It is clearly showen that the proposed solution based on finite strip method can accurately simulate the dynamic response of considered plate under external forces. The scale factors due to small size of the plate and foam-based material will show a remarkable impact on the dynamic response.

This paper presents a careful theoretical investigation into interfacial stresses in damaged RC cantilever beam with bonded prestressed FRP composites, taking into account loading model, shear lag effect and the prestressed composites impact. These composites are used, in particular, for rehabilitation of structures by stopping the propagation of the cracks. They improve rigidity and resistance, and prolong their lifespan. In this paper, an original model is presented to predict and to determine the stresses concentration at the FRP end, with the new theory analysis approach. This research gives more precision related to the others studies which neglect the effect of prestressed composites coupled with the applied loads. A parametric study has been conducted to investigate the sensitivity of interface behavior to parameters such as laminate and adhesive stiffness, the thickness of the laminate and the fiber orientations where all were found to have a marked effect on the magnitude of maximum shear and normal stress in the composite member. The numerical resolution was finalized by taking into account the physical and geometric properties of materials that may play an important role in reducing the stress values. This research is helpful for the understanding on mechanical behaviour of the interface and design of the FRP-damaged RC hybrid structures.

This special issue contains selected papers first presented in a short format at ACSM20 (Advances in Coupled Systems Mechanics) held at the Global Education Center for Engineers (GECE) in Seoul, Korea, August 25~29, 2020. ACSM20 was regrouped with 11 other International Conferences, all placed within the framework of The 2020 World Congress on Advances in Civil, Environmental, & Materials Research (ACEM20)/The 2020 Structures Congress (Structures20).