Abstract: This paper investigates numerically the effect of flexibility for a container ship in calculation vertical bending moment and shear force etc. For this purpose, the hydrodynamic forces are determin...

Abstract: This study investigates the nonlinear vibration and dynamic response of a beam made of functionally graded material (FGM) within the framework of the improved third-order shear deformable theory. The beam is subjected to a concentrated moving load, and the included angle of the load direction and axial direction varies with time. Considering the von Karman geometric nonlinearity, the nonlinear formulations of the FGM beam is derived. The Newmark method in conjunction with the Newton–Raphson iteration is adopted to analyze the dynamic response of the beam. A new method, based on a direct numerical integration technique for the matrix form motion equation, is presented to study the nonlinear vibration of the FGM beam. The proposed method overcomes the problem of signal determination for the solution of the eigenvector equation that often leads to nonconvergence or a false result of the nonlinear eigenvalue equation. In relation to the numerical results, the effects of material property distribution, vibration amplitude on the nonlinear dynamic behavior of the FGM beams, and the energy transference phenomenon are discussed in this paper.

Abstract: In this work, an improved computational method for the prediction of the vibration and noise of a gearbox that considers the flexibility of the shaft is developed. Based on the finite element method (FEM), a coupled dynamic model of a spur gear-shaft-bearing system is established, and the time-varying mesh stiffness (TVMS), the time-varying bearing stiffness (TVBS), and the flexibility of the shaft are considered. The Newmark integration method (NIM) is utilized to obtain the dynamic load of the bearing. Furthermore, the proposed model is validated by experiments. The bearing load is then considered to be the excitation of the housing, and the radiated noise is calculated via the finite element method/boundary element method (FEM/BEM). The effects of the shaft flexibility on the bearing response and radiated noise are discussed based on the proposed method. The results demonstrate that, when the shaft flexibility is considered, the system undergoes the bending vibration of the shaft, and the vibration amplitude and excitation frequency components of the bearing load decrease significantly. Additionally, the main resonance mode of the gearbox is changed, and the radiated noise is enhanced. The effects of the input speed and shaft stiffness on the bearing response and radiated noise are also investigated. The results provide a theoretical basis for the further development of the vibration and noise reduction of gearboxes.

Abstract: In this work, a new method for nonlinear time-history earthquake analysis of 2D steel frames by a fiber plastic hinge method is presented. The beam-column element based on the displacement-based finite element method is established and formulated in detail using a fiber plastic hinge approach and stability functions. Geometric nonlinearities are taken into accounting by stability functions and the geometric stiffness matrix. A nonlinear dynamic algorithm is established based on the combination of the Newmark integration method and the Newton-Raphson iterative algorithm for solving dynamic equations. The proposed program predicts the nonlinear inelastic responses of 2D steel frames subjected to earthquakes as efficiently and accurately as commercial software. This study also shows that the initial residual stresses of steel should be considered in nonlinear inelastic time-history earthquake analysis of 2D steel frames while SAP2000 does not consider the effects of residual stresses.

Abstract: This paper deals with the evaluation of time response analyses of typical aerospace metallic structures. Attention is focussed on detailed stress state distributions over time by using the Carrera ...

Abstract: In this paper, a novel axial dynamic model including the transient force of balance disc is proposed to predict the vibration characteristics of multistage pump rotor system. To obtain the dynamic force, the rotating effect of the rotor system is considered and the Navier–Stokes equations are further simplified on the basis of the geometric structure and inner flow characteristic of the balance disc. In addition, based on finite element method and matrix operation, a novel axial motion model of rotor system is established. The efficient Newmark method is applied to describe the dynamic response of the coupled rotor system. The pressure distribution in axial clearance and the corresponding dynamic force present obvious nonlinear reduction as the axial gap increases from 0.2 mm to 1 mm. The inner chamber pressure is more sensitive to the inlet pressure than the rotating speed, especially when the axial gap is 0.2 mm. Moreover, the axial steady amplitude of the rotor system is directly proportional to the rotating speed and initial axial gap, while it is inversely proportional to the outer radius of the balance disc. In addition, the vibration frequencies for axial vibration are multiple even when the motion of the rotor system is regularly reciprocating. The transient force of the balance disc needs to be considered in the calculation of axial rotor dynamics for the multistage pump. The calculated results can provide references for the design of the balance disc and an axial vibration model of the multistage pump rotor system.

Abstract: We address the electromagnetic problem involving small structures, and put forward an improved, explicit finite-difference time-domain (FDTD) algorithm based on the Newmark discretization with subgridding technique. This algorithm achieves a stable, low-reflection, and straightforward subgridding with an arbitrary grid refinement ratio by adopting hanging variables. The Newmark method is employed to discretize the numerical system generated by the subgridding method. Besides, the Neumann series is used to obtain the inverse of the coefficient matrix. It makes the time-marching explicit and stable with a uniform large time step only determined by the coarse grid size in the whole computational domain. The series expansion avoids the matrix inversion operation, which largely enhances the calculation efficiency compared to the traditional Newmark-FDTD method. Numerical results prove the reliability and robustness of the proposed method.

Abstract: The slope shape is one of the most intuitive factors affecting the seismic stability of a slope. However, current research on this subject is mainly focused on statistical analysis and seismic response law, and the influence on seismic stability evaluation of the slope is rarely discussed. Furthermore, slope shapes are often simplified for easy numerical model building. In view of this, five slope models with different slope shapes are considered, and the time-history analysis method and Newmark method are chosen to evaluate the seismic stability of these slope models under different amplitudes. The purpose of this paper is to compare the seismic stability of slopes with different slope shapes and to study the feasibility of simplifying the slope shape when evaluating the seismic stability of a slope.

Abstract: Efficient and accurate structural parameter identification is critical for the practical application of structural health monitoring. In this paper, a novel algorithm named refracted salp swarm algorithm (RSSA) is proposed and applied to identify structural parameters. Firstly, the basic salp swarm algorithm is improved by refracted opposition-based learning strategy, multi-leader mechanism and adaptive conversion parameter strategy. The superiority of the proposed algorithm is verified by experiments of eight benchmark functions of various types and dimensions. Secondly, a new type of structural parameter identification (SPI) model is established by combining RSSA and the Newmark integration method, which is mainly used to solve the optimization problem based on structural acceleration, thereby identifying structural parameters such as stiffness, mass and damping ratio. Numerical simulation test of seven-floor frame proves that the new proposed RSSA could be successfully applied in the SPI model. Compared with other heuristic algorithms, RSSA can obtain more accurate recognition results under the circumstances incomplete measurement data and low signal-to-noise ratio.

Abstract: The aim of this paper is to study parametric earthquake analysis of thick plates resting on Winkler foundation. The governing equation of the plate is prepared with Mindlin’s thick plate theory. In the dynamic analysis, Newmark method is used for the time integration of the governing dynamic equation. This study investigates the effects of the thickness/span ratio, the aspect ratio, and the boundary conditions on the linear responses of thick plates subjected to earthquake excitations. In the analysis, finite element method is used for spatial integration. For the formulation of the equations of the thick plate theory, a finite element is derived by using higher-order displacement shape functions which is named MT17. This is a fourth-order finite element that shows excellent performance for thick plate analysis. A computer program using finite element method is coded in C++ to analyze the plates clamped or simply supported along all four edges. Graphs are presented that should help engineers in the design of thick plates subjected to earthquake excitations. It is concluded that MT17 element can be effectively used in the earthquake analysis of thick plates. It is also concluded that in general, the changes in the thickness/span ratio are more effective on the maximum responses considered in this study than the changes in the aspect ratio.

Abstract: To determine the influence of temperature on the mechanical properties of crane metal structures, three Q355 alloy steel samples were processed and their elastic moduli were tested at different temperatures using a metal tension test bed. The constitutive equation for the elastic modulus of Q355 alloy steel at different temperatures was predicted using test data and a neural network algorithm. Based on crane structural characteristics and the principle of system dynamics, a coupling vibration model was established that included the crane flexible girder, cabin, trolley, crane, and temperature. System motion equations were established according to the Lagrange equation, and the approximate solution of nonlinear system vibration was solved by the direct integration method (the Newmark method). The dynamic characteristics of the main beam and cabin were analyzed at different temperatures, as well as safety during service. The results show that, with increasing temperature, the maximum midspan displacement of the main beam increases gradually, by 14.3%, 21.4%, and 57.1% at temperatures of 300°C, 400°C, and 600°C, respectively. The cabin vibration displacement increases with temperature, by up to 32.5% at 600°C, but the influence of temperature on cabin vibration acceleration is not obvious. It was concluded that the influence of temperature on the dynamic characteristics of the main beam must be considered during the design stage of cranes. The proposed model and analysis method provide a theoretical basis for the design of casting cranes according to temperature.

Abstract: In present work, the three-dimensional constitutive equations considering hygrothermal conditions are derived firstly, and governing equations are established subsequently. Then the finite differen...

Abstract: The static/dynamic analysis of the thin plate is of great importance in engineering problems. Based on the complexity of the problem, only for some important cases of boundary conditions, analytical solutions were derived. While in general case, numerical approaches should be implemented to solve the problem. The discrete singular convolution (DSC) technique is one of the most accurate methods. Until now, this method is difficult to be used for the determination of the static and dynamic responses for plates with semi-rigid boundary conditions. Based on the fact that DSC method using the Taylor approach (DSC-T) is recently used for the analysis of the free vibration of free and semi-rigid edges rectangular plate, this study aims to extend the application of the DSC-T methods to the static and dynamic analysis of the thin rectangular plate restrained with the dowels and resting on elastic foundation. The DSC-T approach is extended to the resolution of the static case of a dowelled plate, and with the combination of the Newmark scheme, to the case of the dynamic load. The results showed the applicability of the studied method for the determination of static and dynamic responses of the plates. Besides, it is shown that there is a linear relationship between the value of the depth and the decrement of the modified Vlasov soil. The value of the logarithmic decrement of the soil is highly influenced by the thickness of the plate namely for membranes and very thin plates. The DSC-T method could be recommended for the engineering design of a variety of civil structures.

Abstract: The prediction of liquefaction-induced lateral spreading is an important geotechnical engineering problem. In this paper, a simplified prediction method based upon Newmark sliding block analysis was proposed to predict the liquefaction-induced lateral spreading. The acceleration time history beneath the liquefied soil (starting from the triggering time of liquefaction) and the postliquefaction yield acceleration corresponding with the residual shear strength of liquefiable soil were used in the Newmark sliding block analysis. One-dimensional effective stress analysis was conducted to obtain the motion beneath the liquefied soil and the liquefaction time. Limit equilibrium analysis was employed to determine the postliquefaction yield acceleration using the residual shear strength of liquefied soil, which correlated with the equivalent clean sand SPT blow count of the liquefied sand. This method was evaluated against five well-documented case histories and the predicted displacements of lateral spreading were subsequently compared with the observed displacements. In addition, the lateral spreading predicted by the rigorous Newmark sliding block method and numerical difference analysis was presented. Based on the statistical analysis of the displacement ratios, it suggested that the method proposed in this paper identified the triggering time of liquefaction and provided a reasonable prediction of the liquefaction-induced lateral spreading with an RMSE (root mean square error) of 0.63, a standard deviation of 0.40, and a CV (coefficient of variance) of 0.60, respectively.

Abstract: The strength, stiffness, and stability check calculations and the effect of earthquakes should be considered in the design of cable-stayed arch bridges with collaborative systems. This study aims to investigate the dynamic performance and structural response of cable-stayed arch bridges under seismic action. The space analysis model is enhanced of the Xiang Feng River Bridge using finite element software Midas Civil, whose lower foundation considers the effects of piles and soil. Firstly the vibration period, vibration frequency, and modal characteristics are computed, thus the dynamic performance is summarized of the bridge. Then, a proper seismic wave is selected according to engineering conditions and in terms of three orthogonal directions: inputting the adjusted El Centro seismic wave, considering Rayleigh damping, and calculating via the Newmark method. Furthermore, a time-history response analysis under the action of one-dimensional and multidimensional earthquake is performed. Lastly, the results of the response analysis is compared and the behavior characteristics of arch bridge is summarized under seismic action. The results show that the transverse stability problem of bridges is prominent and should be the focus of antiearthquake fortification, the inclined cable tower of this bridge is not conducive to the earthquake resistance of the structure in comparison with the vertical cable tower. and the influence of horizontal and vertical earthquake actions should be considered in antiearthquake designs.

Abstract: In some cases, impulse- or shock-type excitations as the dynamic loading are inevitable, and obtaining proper response with the well-known numerical methods is not easy. This paper focuses on dynamic response estimation against short-time loading with an updated finite element model using frequency response functions (FRF) and particle swarm optimization (PSO) technique. Because there is not an analytical method for assessing the numerical responses under shock-type excitations, in this paper, experimental tests are designed on a laboratory scale to evaluate the numerical responses. The vibration responses of the system against shock loading are compared with the Newmark average acceleration scheme and also with experimental data. The results reveal that the unconditionally stable Newmark method against regular loads has an appropriate performance. Still, under short-time loading, it faces numerical damping error, and this method should not be blindly applied under shock-type loads.

Abstract: In this paper, we present a formulation and a numerical simulation method for earthquake-induced collisions between a seismically base-isolated building structure and its surrounding moat walls. The base isolator is assumed to undergo plastic deformation. We use the conventional shear building model for a superstructure. Based on nonsmooth mechanics, we formulate a measure differential inclusion that describes the time evolution of the entire structure. For numerical computation, we apply Moreau’s time-stepping scheme to the presented formulation. As a consequence, we solve a quadratic programming problem for each time-step. Our preliminary numerical experiments demonstrate that the presented method is more robust and numerically stable compared with the conventional Newmark method. We also present two numerical examples of mid-rise base-isolated building structures.

Abstract: A two-step explicit acceleration integration method (EAIM2) and a three-step explicit acceleration integration method (EAIM3), which are entirely explicit time integration algorithms, are proposed based on acceleration time history. The computation efforts and costs can be observably reduced on account of avoiding matrix inversion and iteration processes in nonlinear systems. Four nonlinear systems are employed to analyze the EAIM2, the EAIM3, the HHT-$$\upalpha $$ method, the Newmark explicit method and the generally used Newmark method for comparison purposes. The results show that the highest orders of accuracy of the EAIM2 and the EAIM3 are all of second order. The stability of the proposed methods can remain in a critical state in undamped systems. The puny energy ratio and the periodic energy growth and decay manifest that the proposed methods are endowed with favorable nonlinear stability. The amplitude attenuation of the proposed methods is zero. The proposed methods and the CDM possess the same period elongation. The period error of the proposed methods is smaller than that of the Newmark method in the stability interval. The EAIM2 and the EAIM3 possess the lowest computation efforts at the same accuracy level in the above-mentioned integration methods.

Abstract: The node-based smoothed radial point interpolation method combined with the asymptotic homogenization method was proposed, as an addition to the finite element method, to address the static and dyn...

Abstract: Based on the general Biot theory of saturated porous media, a modified time-discontinuous Galerkin finite element method (MDGFEM) is presented to simulate the structural dynamics and wave propagation problems of gas-saturated coal subjected to impact loading. Numerical results of one dimension and two dimensions show that the present MDGFEM possesses better abilities and provides much more accurate solutions than the traditional Newmark method and previous DGFEM for the impact problem. It can effectively capture the discontinuities of the wave and filter out the effects of spurious numerical oscillation induced by high-frequency impulsive load. The results can provide a technological basis for the research of the prevention of coal and gas dynamic disasters under deep mining. And the method could be useful for the further numerical research of coal-rock-gas coupling problems and coal-gas-heat coupling problems subjected to impact loading.

Abstract: This article deals with the dynamic analysis in pad concrete foundation containing Silica nanoparticles (SiO2) subject to seismic load. In order to control the foundation smartly, a piezoelectric layer covered the foundation. The weight of the building by a column on the foundation is assumed with an external force in the middle of the structure. The foundation is located in soil medium which is modeled by spring elements. The Mori-Tanaka law is utilized for calculating the equivalent mechanical characteristics of the concrete foundation. The Kevin-Voigt model is adopted to take into account the structural damping. The concrete structure is modeled by a thick plate and the governing equations are deduced using Hamilton\'s principle under the assumption of higher-order shear deformation theory (HSDT). The differential quadrature method (DQM) and the Newmark method are applied to obtain the seismic response. The effects of the applied voltage to the smart layer, agglomeration and volume percent of SiO2 nanoparticles, damping of the structure, geometrical parameters and soil medium of the structure are assessed on the dynamic response. It has been demonstrated by the numerical results that by applying a negative voltage, the dynamic deflection is reduced significantly. Moreover, silica nanoparticles reduce the dynamic deflection of the concrete foundation.

Abstract: This paper proposes a methodology to obtain the transient response of structural system interacting with soil-foundation schemes supported by viscoelastic soils. The structure and soil are divided into sub-systems. The time domain solution for each subsystem is formulated by an appropriated methodology. The equations of motion of structure are solved by Newmark integration algorithm. The transient response of the soil is obtained by a convolution integral. The convolution integral uses transient impulse response of viscoelastic soils. Newmark and convolution algorithms are formulated as input and output schemes, which, in turn, are plugged to the time stepping iterative algorithm. The scheme is applied to vertical response of a dynamical system interacting with a massless foundation laying on a soil modelled as a three-dimensional homogeneous viscoelastic half-space. For two distinct external forces, the resulting coupled displacements, interface forces, errors and number of iterations within each time step are provided.