Journal articles on the topic 'Newmark implicit integration'

The modified equations for PC-Newmark method and OS (operator-splitting) method were derived, which could be applied to the numerical solution for the non-linear equation encountered in real time on-line test. The structure with FPS seismic isolation system was divided into three substructures, namely the FPS system, the experiment substructure and the computation substructure. The explicit algorithm is applied to the first two substructures and the implicit algorithm to the third one in order to loosen the stability limitation. The numerical solution for a 7 DOF structural model has proven the alleviation for stability requirement.

A family of new explicit time-integration method is proposed herein, which inherits the numerical characteristics of any existing implicit Runge–Kutta algorithms for a linear conservative system. Based on an exact derivation of the increment of mechanical energy, the method proposed is demonstrated to be unconditionally stable. Also, the stability condition of the proposed method is derived when applied to solving a nonlinear system. The characteristics of the proposed method are investigated by observing the mechanical-energy time history of a nonlinear conservative system. The numerical results can be explained by the stability condition derived in the nonlinear regime. Finally, the computational accuracy and efficiency between the Newmark time integration method and the proposed explicit method are compared in solving the dynamic response of a couple of linear oscillators.

The aeroelastic coupling dynamic equation of helicopter rotor is essentially a set of nonlinear and inhomogeneous equations with large rigidity, in which the inhomogeneous term is a function of blade motion and aerodynamic load. In this paper, the precise time integration method and its derived formats are introduced to solve the rotor blade dynamic equation, and the Duhamel integral item can be calculated by various numerical methods. In terms of computational accuracy and numerical stability, the precise Kutta method and high precision direct integration method (HPD method) are carefully selected to compare with classical Runge–Kutta method numerically. HPD method is used to solve the rotor blade dynamic equation, and the transient response of the rotor blade is examined by Newmark and implicit trapezoidal methods. Results indicate that HPD method dominates the classical Runge–Kutta method in step size independence, and gets close to implicit methods in numerical stability and accuracy for dynamic equation of helicopter rotor blade.

Abstract In recent years, the pounding effect during earthquake is a subject of high significance for structural engineers. In this paper, a state space formulation of the equation of motion is used in a MATLAB code. The pounding forces are calculated using nonlinear viscoelastic impact element. The numerical study is performed on SDOF structures subjected by 1940 EL-Centro and 1977 Vrancea N-S recording. While most of the studies available in the literature are related to Newmark implicit time integration method, in this study the equations of motion in state space form are direct integrated. The time domain is chosen instead of the complex one in order to catch the nonlinear behavior of the structures. The physical nonlinear behavior of the structures is modeled according to the Force Analogy Method. The coupling of the Force Analogy Method with the state space approach conducts to an explicit time integration method. Consequently, the collision is easily checked and the pounding forces are taken into account into the equation of motion in an easier manner than in an implicit integration method. A comparison with available data in the literature is presented.

In this article, numerical approach is proposedfor dynamic behavior of symmetrical sandwich beams with viscoelastic core under movingload using the Hamilton's principle formulation and the finite element method solution. The dynamic responses are obtained for different configurations using the modal superposition method and the implicit Newmark integration scheme. The analysis shows that the viscoelastic damping has a significant effect on the vibration behavior involving the improvement of the damping of the structure. The parametric study of the effect of the configuration parameters shows that the sandwich structure has more dissipative capacities of vibratory energy by adopting adequate configurations to the structure.

Abstract Pounding effects during earthquake is a subject of high significance for structural engineers performing in the urban areas. In this paper, two ways to account for structural pounding are used in a MATLAB code, namely classical stereomechanics approach and nonlinear viscoelastic impact element. The numerical study is performed on SDOF structures acted by ELCentro recording. While most of the studies available in the literature are related to Newmark implicit time integration method, in this study the equations of motion are numerical integrated using central finite difference method, an explicit method, having the main advantage that in the displacement at the ith+1 step is calculated based on the loads from the ith step. Thus, the collision is checked and the pounding forces are taken into account into the equation of motion in an easier manner than in an implicit integration method. First, a comparison is done using available data in the literature. Both linear and nonlinear behavior of the structures during earthquake is further investigated. Several layout scenarios are also investigated, in which one or more weak buildings are adjacent to a stiffer building. One of the main findings in this paper is related to the behavior of a weak structure located between two stiff structures.

In order to solve 3-D dynamic problem for large-scale structure, based on HDDM (Hierarchical Domain Decomposition Method) method, 3-D dynamic finite element parallel computing method of large-scale structure is studied. In this paper, BDD method and Newmark-β average acceleration method in time integration is used. Based on ADVENTRUE program, the corresponding linear implicit transient dynamic parallel program which is based on the MPI parallel environment and can be used in shared memory and distributed memory parallel computer is prepared. Several pre-conditioners are contrasted using some examples, and the results show that BDD preconditioner or BDD-DIAG preconditioner can be used in 3-D dynamic analysis for large-scale structure.

The complex variable moving least-squares (CVMLS) approximation is discussed in this paper, and the mathematical and physical meaning of the complex functional in the CVMLS approximation is presented. With the CVMLS approximation, the trial function of a two-dimensional problem is formed with a one-dimensional basis function. Then combining the CVMLS approximation and the Galerkin weak form, we investigate the complex variable element-free Galerkin (CVEFG) method for two-dimensional elastodynamics problems. The penalty method is used to apply the essential boundary conditions, and the implicit time integration method, which is the Newmark method, is used for time history analysis. Then the corresponding formulae of the CVEFG method for two-dimensional elastodynamics problems are obtained. For the purposes of demonstration, some selected numerical examples are solved using the CVEFG method. Compared with the EFG method, the CVEFG method has greater precision.

AbstractThe virtual element method (VEM) for dynamic analyses of nonlinear elasto-plastic problems undergoing large deformations is outlined within this work. VEM has been applied to various problems in engineering, considering elasto-plasticity, multiphysics, damage, elastodynamics, contact- and fracture mechanics. This work focuses on the extension of VEM formulations towards dynamic elasto-plastic applications. Hereby low-order ansatz functions are employed in three dimensions with elements having arbitrary convex or concave polygonal shapes. The formulations presented in this study are based on minimization of potential function for both the static as well as the dynamic behavior. Additionally, to overcome the volumetric locking phenomena due to elastic and plastic incompressibility conditions, a mixed formulation based on a Hu-Washizu functional is adopted. For the implicit time integration scheme, Newmark method is used. To show the model performance, various numerical examples in 3D are presented.

Purpose – The purpose of this paper is to study the influence of friction phenomenon generated by a disc brake on the dynamic behaviour of a one-stage spur gear. Design/methodology/approach – A theoretical model is proposed and is based on both theories of Coulomb and Dahl in order to analyse the influence of disc brake friction phenomenon on the dynamic behaviour of one-stage spur gear transmission. Findings – The influence of brake friction on the dynamic behaviour of the transmission is investigated using the proposed model and leads to observe higher vibration levels when the braking is occurring as well as the emergence of significant efforts at the gear teeth. Originality/value – A new numerical model based on the implicit numerical integration technique of Newmark coupled with Newton-Raphson method is proposed to study the influence of friction phenomenon of a disc brake on the dynamic behaviour of one-stage spur gear.

For its construction convenience and structure integrity, cofferdams are widely employed in port engineering. Past experience has shown that cofferdam are subjected to damage due to earthquake excitations. Numerical analyses with both response spectrum and step-by-step integration methods are conducted by using Lanczos eigenvalue extraction technique to obtain natural frequencies and modes, and solving dynamic equations with Newmark implicit method to consider geometric nonlinearity. The computational results show that the natural frequency of cofferdam system is low and the horizontal translation stiffness of cofferdam in positive direction is higher than that in negative direction. Under seismic excitation, the displacement response of inner steel sheet is much more obvious than that of outer one. And the distribution of horizontal displacements in steel sheets presents the characteristics that the corresponding values increase with their heights in the cofferdam system. On the contrary, the deviatonic stresses of cofferdam decrease with the augments of height.

A corotational finite element formulation for two-dimensional beam elements with geometrically nonlinear behavior is presented. The formulation separates the rigid body motion from the pure deformation which is always small relative to the corotational element frame. The stiffness matrices and the mass matrices are evaluated using both Euler-Bernoulli and Timoshenko beam models to reveal the shear effect in thin and thick beams and frames. The nonlinear equilibrium equations are developed using Hamilton’s principle and are defined in the global coordinate system. A MATLAB code is developed for the numerical solution. In static analysis, the code employed an iterative method based on the full Newton-Raphson method without incremental loading, while, in dynamic analysis, the Newmark direct integration implicit method is also utilized. Several examples of flexible beams and frames with large displacements are presented. Not only is the method simple and time-saving, but it is also highly effective and highly accurate.

A numerical model using the Finite Element Method (FEM) for the nonlinear static and dynamic analysis of reinforced concrete (RC) beams, plates and shells is presented in this work. For this purpose, computer programs based on plasticity theory and with crack monitoring capabilities are developed. The static analysis of RC shells up to failure load is carried out using 9-node degenerated shell finite elements while 20-node brick finite elements are used for dynamic applications. The elasto-plastic constitutive law for concrete is coupled with a strain-rate sensitive model in order to take into account high loading rate effect when transient loading is intended. The implicit Newmark scheme with predictor and corrector phases is used for time integration of the nonlinear system of equations. In both cases, the steel reinforcement is considered to be smeared and represented by membrane finite elements. Various benchmark examples are solved with the present numerical model and comparisons with other published data are performed. For all examples, the path failure, collapse loads and failure mechanism is reproduced with great accuracy.

This article presents a simple procedure for predicting time-domain vibrational behaviors of a multiple degrees of freedom mechanical system with dry friction. The system equations of motion are discretized by means of the implicit Bozzak–Newmark integration scheme. At each time step, the discontinuous frictional force problem involving both the equality and inequality constraints is successfully reduced to a quadratic mathematical problem or the linear complementary problem with the introduction of non-negative and complementary variable pairs (supremum velocities and slack forces). The so-obtained complementary equations in the complementary pairs can be solved efficiently using the Lemke algorithm. Results for several single degree of freedom and multiple degrees of freedom problems with one-dimensional frictional constraints and the classical Coulomb frictional model are obtained using the proposed procedure and compared with those obtained using other approaches. The proposed procedure is found to be accurate, efficient, and robust in solving non-smooth vibration problems of multiple degrees of freedom systems with dry friction. The proposed procedure can also be applied to systems with two-dimensional frictional constraints and more sophisticated frictional models.

Concrete fracture can be simulated in static regime, however, it is a dynamical process. For very slow loading rates, the kinetic energy is negligible compared to the energy dissipated by fracturing, and the influence of inertia can be neglected. In all other cases, neglecting the influence of inertia forces can lead to improper results. With increasing loading rate, increase in strength and energy dissipation as well as changes in crack pattern can be observed. The contribution presents dynamical simulations of experiments on concrete specimens under various displacement rates, from very slow, quasi-static, to high displacement rates. The simulations are calculated using discrete particle model, the material is represented by a system of interconnected ideally rigid polyhedral particles. The solution of equations of motion is calculated using implicit time integration Newmark scheme. The constitutive behavior of the material is strain rate independent. For high strain rates the influence of inertia forces dominates and is mainly responsible for increase in loading forces as well as for change in the crack pattern and crack branching. The results obtained with the model are compared to experimental data from literature.

This paper studies the dynamic viscoelastic response of functionally graded (FG) thick 2D cantilever and simply supported beams under dynamic pulse load, for the first time. A point load applied at a specific spatial point is described as a time-pulse sinusoidal load. Two-dimensional plane-stress constitutive equation is exploited to describe the local stress–strain relation through the beam. The gradation of material is depicted by generalized power law function through the layer thickness across beam thickness. The Kelvin–Voigt viscoelastic model is proposed to describe material damping of structure. Lagrange’s equation is employed to derive governing motion equation. A finite element method (FEM) is exploited to discretize the spatial domain of 2D beam structure by using 12-node 2D plane element. Numerical Newmark implicit time integration method is proposed to solve the equation of motion incrementally and get the response of beam structure. Two types of boundary conditions are considered in the numerical examples. In numerical results, effects of stacking sequence, geometry parameters and material gradation index and viscoelasticity coefficients on the displacement-time response of layered functionally graded viscoelastic deep beams for different boundary conditions.

In order to further reveal the vertical random vibration characteristics of railway vehicles, using the system engineering method, taking the passenger, the train system, and the track system (ballast track) as a unified whole, a passenger-train-track vertical coupling dynamic model is established, and the vibration differential equations of the model are derived. In the model, passengers are regarded as a single-degree-of-freedom system attached to the bottom of the carriage, the train system is represented as a 10-degree-of-freedom multi-rigid body model, the track system is regarded as the infinite long Euler beam model with three layers of continuous elastic point support, and the Hertz nonlinear elastic contact theory is applied to the wheel and rail coupling relationship. Based on this, the time-domain numerical solution of the passenger-train-track vertical coupling dynamic model is given by using Newmark- β implicit integration algorithm, and the correctness of the model is verified by the real vehicle test. This study can provide some theoretical basis for the design of railway vehicles and provide fundamentals for the coordinated control and system optimization of railway vehicle ride comfort.

ABSTRACTThe objective of this work is to provide a reliable numerical model using the finite element method (FEM) for the dynamic analysis of reinforced concrete (RC) structures. For this purpose, a computer program based on a strain-rate sensitive elasto-plastic theory is developed using 3D brick finite elements. The implicit Newmark scheme with predictor and corrector phases is used for time integration of the nonlinear system of equations. In addition, the steel reinforcement is considered to be smeared and perfectly adhered to concrete and represented by membrane finite elements. Two benchmark examples are analyzed with the present numerical model and results are compared with those obtained by other authors. The present numerical model is able to reproduce the path failure, collapse loads and failure mechanism within an acceptable level of accuracy. Keywords.-Reinforced concrete (RC) structures, Finite element method (FEM). RESUMENEl objetivo de este trabajo es presentar un modelo numérico confiable usando el método de los elementos finitos (MEF) para el análisis dinámico de estructuras de concreto reforzado. Con este propósito, un programa de cómputo basado en la teoría de elasto-plasticidad con sensibilidad a la velocidad de deformación es desarrollado usando elementos finitos tridimensionales. El procedimiento de Newmark es adoptado para la integración en el tiempo del sistema no linear de ecuaciones. Además, se supone que el acero de refuerzo está perfectamente distribuido e adherido al concreto, siendo representado por elementos finitos de membrana. Dos ejemplos son solucionados con el presente modelo numérico y los resultados obtenidos son comparados con los resultados de otros autores. Para todos los casos, la trayectoria de falla, la carga de colapso y el mecanismo de falla son reproducidos con suficiente precisión. Palabras clave.- Estructuras de concreto reforzado, Método de los elementos finitos (MEF).

A fully coupled time-domain ship hydroelasticity problem focusing on a springing phenomenon is considered in this study using a hybrid boundary element method (BEM) finite element method (FEM) scheme. The fluid domain surrounding a flexible vessel is handled with a boundary element method adopting a higher-order B-spline Rankine panel method. The structural domain is modeled by a finite element method relying on the one-dimensional beam element, which is able to capture the coupling effect between torsion and bending as well as warping distortion. Coupling between the two subdomains is realized by the Newton method in which an exact Jacobian matrix is derived by solving both fluid and structure tangent problems. The calculation is repeated until the solution reaches convergence. Thanks to the positive aspects of this implicit scheme, numerical instability related to the time integration can be avoided without relying on infinite frequency added mass, which is inevitable when an explicit scheme is used. Moreover, a direct integration scheme, such as the Newmark-β method, for structural problems can be used, and this formulation can be easily extended to the case with structural nonlinear effect, such as large deformation. The developed computer program is validated through comparison with published experimental data, ending up with good correspondence between the two results. Validation is also achieved through a comparative study on rigid body motion with an existing six degrees of freedom (6-DOF) ship motion program.

In this research, the effect of bedrock stiffness on seismic performance of roller compacted concrete (RCC) dam is evaluated using probabilistic analysis. Due to the geometry and behavior of RCC dams, a two-dimensional modeling was selected for system. Ansys software is used for modeling and analysis of dam-reservoir- foundation system. Newmark implicit time integration scheme is developed to solve the time-discretized equations which are an unconditionally stable method. The Watana dam, due to San Fernando earthquake has been selected as a case study. In order to propagate the parametric sensitivity to the seismic performance of the system, Monte Carlo simulation with Latin hypercube sampling (LHS) method is used as a probabilistic method and uncertainty analysis. The sensitivity of responses under seismic loading is reliably examined utilizing different values of ratio of bedrock stiffness to body concrete stiffness as random inputs. Consider to obtained results, it is revealed that the bedrock stiffness how can effect on seismic behavior of concrete gravity dams due to earthquake. Regarding the safety of dams due to compressive stresses, various ways have been assessed to investigate the induced tensile stress in the heel and the results have been investigated. Finally, appropriate range of the ratio of bedrock stiffness to concrete stiffness of dam body is presented to assess the safety design.

Capabilities for the analysis of combined viscous and plastic behavior have been added to an existing finite element computer program for two-dimensional elastic-plastic calculations. This program (PAPSTB) has been formulated for elastic-plastic stress and deformation analyses of two-dimensional and axisymmetric structures. It has the ability to model large strains and large deformations of elastic-perfectly plastic, multi-linear hardening, or power-hardening materials. The program is based on incremental plasticity theory with a von Mises yield criterion. Time dependent behavior has been introduced into the PAPSTB program by adding a viscous strain increment to the elastic and plastic strain increment to form the total strain increment. The viscous calculations presently employ a power-law relationship between the viscous strain rate and the effective stress. The finite element code can be easily modified to handle more complex viscous models. The Newmark method for time integration is used, i.e., an input parameter is included which enables the user to vary the time domain approximation between forward (explicit) and backward (implicit) difference. Automatic time stepping is used to provide for stability in the viscous calculations. It is controlled by an input parameter related to the ratio of the current viscous strain increment to the total strain. The viscoplastic capabilities of the PAPSTB program are verified using the axisymmetric problem of an internally pressurized, thick-walled cylinder. The transient viscoplastic case is analyzed to demonstrate that the elastic-perfectly plastic solution is obtained as a steady-state condition is approached. The influence of varying the time integration parameter for transient viscoplastic calculations is demonstrated. In addition, the effects of time step on solution accuracy are investigated by means of the automatic time stepping algorithm in the program. The approach is then applied to a simple forging problem of cylinder upsetting.

The finite element method (FEM) is a numerical technique well suited to solving problems of elastic wave propagation in complex geometries and heterogeneous media. The main advantages are that very irregular grids can be used, free surface boundary conditions can be easily taken into account, a good reconstruction is possible of irregular surface topography, and complex geometries, such as curved, dipping and rough interfaces, intrusions, cusps, and holes can be defined. The main drawbacks of the classical approach are the need for a large amount of memory, low computational efficiency, and the possible appearance of spurious effects. In this paper we describe some experience in improving the computational efficiency of a finite element code based on a global approach, and used for seismic modeling in geophysical oil exploration. Results from the use of different methods and models run on a mini-superworkstation APOLLO DN10000 are reported and compared. With Chebyshev spectral elements, great accuracy can be reached with almost no numerical artifacts. Static condensation of the spectral element's internal nodes dramatically reduces memory requirements and CPU time. Time integration performed with the classical implicit Newmark scheme is very accurate but not very efficient. Due to the high sparsity of the matrices, the use of compressed storage is shown to greatly reduce not only memory requirements but also computing time. The operation which most affects the performance is the matrix-by-vector product; an effective programming of this subroutine for the storage technique used is decisive. The conjugate gradient method preconditioned by incomplete Cholesky factorization provides, in general, a good compromise between efficiency and memory requirements. Spectral elements greatly increase its efficiency, since the number of iterations is reduced. The most efficient and accurate method is a hybrid iterative-direct solution of the linear system arising from the static condensation of high order elements. The size of 2D models that can be handled in a reasonable time on this kind of computer is nowadays hardly sufficient, and significant 3D modeling is completely unfeasible. However the introduction of new FEM algorithms coupled with the use of new computer architectures is encouraging for the future.

Based on Newmark’s step-by-step implicit integration method, an improved algorithm for promoting computing efficiency is put forward in this paper. Implicit integration method and improved algorithm were applied respectively to analyze the dynamic responses of a tunnel due to train vibration. Results indicated that the improved algorithm enhanced remarkably the efficiency of computation.

Современные вычислительные средства с помощью новейших компьютерных технологий дают возможность производить моделирование и расчёт научных и прикладных задач в самых разных сферах деятельности. Новые возможности, позволяют ставить и решать многие комплексные научные и технические задачи морской гео- и гидрофизики, среди которых особенно актуальны в настоящее время следующие: создание аппаратуры для изучения и измерения электрического и магнитного полей в воде; исследование электрических явлений в море для определения их связи с другими физическими процессами; изучение магнитогидродинамических процессов, возникающих из-за движения морской воды в магнитном поле Земли и многие другие Некоторые прикладные задачи требуют физически верного описания движения твёрдого тела, как в жидкой среде, так и на границе раздела сред, например, «газ–жидкость». Кроме того, подобного рода движения могут происходить при наличии изменчивости физических (например, электромагнитного) полей, которые необходимо учитывать. Решение подобных задач стало возможным с помощью современных вычислительных комплексов. Однако при этом следует иметь в виду, что сложный характер взаимодействия гидродинамического и электромагнитного полей обуславливает необходимость рассмотрения достаточно упрощенных моделей, описывающих основные закономерности изучаемых явлений. В настоящей работе представлены результаты численного моделирования генерации индуцированного магнитного поля, вызванной колебательным движением твёрдого шара, с помощь вычислительного комплекса ANSYS.CFX. Шар совершает вынужденные колебания на границе раздела «морская вода – воздух». Модельная постановка задачи позволяет лучше понять механизм генерации магнитного поля, обусловленный движением твёрдого заряженного тела в проводящей среде. Рассматриваемое твердое тело – шар - моделируется набором 2D областей, формирующими его поверхность, при этом сетка движется по его поверхности в соответствии с решением уравнений динамики последнего. Решение уравнений прямолинейного движения выполняется с помощью дискретизации по неявной схеме интегрирования Ньюмарка. При этом используется 2й порядок точности. Для расчета параметров магнитного поля решалась система уравнениймагнитной гидродинамики, реализованная в вычислительной структуре комплекса ANSYS. CFX. Modern computing facilities with the help of the latest computer technologies allow modeling and calculating scientific and applied problems in various fields of activity. New modeling capabilities make it possible to pose and solve many complex scientific and technical problems of marine geo- and hydrophysics, among which the following are especially relevant now: creation of equipment for studying and measuring electric and magnetic fields in water; study of electrical phenomena at sea to determine their relationship with other physical processes; study of magnetohydrodynamic processes arising from the movement of sea water in the Earth's magnetic field and many others Some applied problems require a physically correct description of the motion of a solid, both in a liquid medium and at the interface between media, for example, "gas-liquid". In addition, this kind of motion can occur in the presence of variability of physical (for example, electromagnetic) fields, which must be taken into account. The solution of such problems has become possible with the help of modern computing systems. However, it should be borne in mind that the complex nature of the interaction of hydrodynamic and electromagnetic fields necessitates the consideration of rather simplified models, which, however, "grasp" the essence and describe the basic laws of the studied phenomena. This paper presents the results of numerical simulation of the generation of an induced magnetic field caused by the oscillatory motion of a solid ball using the ANSYS.CFX computer complex. The ball makes forced vibrations at the "sea water - air" interface. The model formulation of the problem makes it possible to better understand the mechanism of magnetic field generation caused by the motion of a solid charged body in a conducting medium. The considered rigid body - a sphere - is modeled by a set of 2D regions that form its surface, while the mesh moves along its surface in accordance with the solution of the equations of the dynamics of the latter. The solution of the equations of rectilinear motion is performed by discretization according to the implicit Newmark integration scheme. In this case, the 2nd order of accuracy is used. To calculate the parameters of the magnetic field, the system of equations of magnetohydrodynamics was solved, implemented in the computational structure of the ANSYS complex. CFX.

Various forms of academic elitism exclude "professional" education, including medicine, engineering, and law, from the academic curriculum on grounds of the intrinsic, i.e., non-instrumental value of university education and scholarship.In this paper, I shall explore arguments from J.S. Mill, Cardinal John Newman, and I. Kant to this effect, attempting to clarify what non-instrumental value they find in university education and scholarship, and why it should serve to exclude the professional, and sometimes the scientific and the technological. [1] In Kant’s case, I shall point out more integrative options implicit in his approach. I shall than look at some contemporary resolutions of these issues, namely, the relation of knowledge and university education to economic usefulness, on the one hand, and to a free and democratic society, on the other, in the writings of Philip Kitcher (2011), Jacques Derrida (1983) and Jürgen Habermas (1992).[1] An earlier version of this paper was presented at a conference entitled: "curricula and Humanistic Scholarship: Between Tacit Knowledge and Public Discourse," sponsored by The Van Leer Jerusalem Institute, The Sidney M. Edelstein Center at the Hebrew University of Jerusalem, The Cohn Institute for the History and Philosophy of Science and Ideas and The Minerva Humanities Center at Tel-Aviv University, and the Volkswagen Stiftung. The author wishes to thank the organizers of the conference, and particularly Prof. Rivka Feldhai and Prof. Gabi Motzkin.

Discrete elastic rods (DER) algorithm presents a computationally efficient means of simulating the geometrically nonlinear dynamics of elastic rods. However, it can suffer from artificial energy loss during the time integration step. Our approach extends the existing DER technique by using a different time integration scheme—we consider a second-order, implicit Newmark-beta method to avoid energy dissipation. This treatment shows better convergence with time step size, specially when the damping forces are negligible and the structure undergoes vibratory motion. Two demonstrations—a cantilever beam and a helical rod hanging under gravity—are used to show the effectiveness of the modified discrete elastic rods simulator.

Abstract While Iwan elements have been used to effectively model the stiffness and energy dissipation in bolted joints, integrating the equations of motion of these elements is fairly expensive since implicit schemes, such as Newmark’s methods, need to be used. This paper presents a method of simulating dynamic systems containing nonlinear Iwan elements that significantly reduce the computation cost by using closed-form expressions for stiffness and damping in the microslip regime and an averaging method for regions of time in which no external force is applied. The proposed algorithm is demonstrated on a single degree-of-freedom (SDOF) system to evaluate the range over which it retains accuracy and the improvement in performance it offers. Although the current implementation is limited to SDOF systems, it can be used to simulate the response of each mode in structures exhibiting weak nonlinearity that can be modeled using the modal Iwan approach. To verify this, the dynamic response of a finite element model of a beam assembly, integrated using the Newmark-β method, has been compared with its equivalent modal model integrated using the proposed algorithm. The results show that the algorithm accurately predicts the response in a fraction of the time taken by implicit integration schemes, so long as the modes remain uncoupled and weakly nonlinear.

A new family of time integration methods is formulated. The recommended technique is useful and robust for the loads with large variations and the systems with nonlinear damping behavior. It is also applicable for the structures with lots of degrees of freedom, and can handle general nonlinear dynamic systems. By comparing the presented scheme with the fourth-order Runge–Kutta and the Newmark algorithms, it is concluded that the new strategy is more stable. The authors’ formulations have good results on amplitude decay and dispersion error analyses. Moreover, the family orders of accuracy are [Formula: see text] and [Formula: see text] for even and odd values of [Formula: see text], respectively. Findings demonstrate the superiority of the new family compared to explicit and implicit methods and dissipative and non-dissipative algorithms.

AbstractIn this paper, an efficient and robust methodology to simulate saturated soils subjected to low-medium frequency dynamic loadings under large deformation regime is presented. The coupling between solid and fluid phases is solved through the dynamic reduced formulation $$u-p_\mathrm{w}$$ u - p w (solid displacement – pore water pressure) of the Biot’s equations. The additional novelty lies in the employment of an explicit two-steps Newmark predictor-corrector time integration scheme that enables accurate solutions of related geomechanical problems at large strain without the usually high computational cost associated with the implicit counterparts. Shape functions based on the elegant Local Maximum Entropy approach, through the Optimal Transportation Meshfree framework, are considered to solve numerically different dynamic problems in fluid saturated porous media.

An integration algorithm, which integrates the most important advantage of explicit methods of the explicitness of each time step and that of implicit methods of the possibility of unconditional stability, is presented herein. This algorithm is analytically shown to be unconditionally stable for any linear elastic and nonlinear systems except for the instantaneous stiffness hardening systems with the instantaneous degree of nonlinearity larger than 43 based on a linearized stability analysis. Hence, its stability property is better than the previously published algorithm (Chang, 2007, “Improved Explicit Method for Structural Dynamics,” J. Eng. Mech., 133(7), pp. 748–760), which is only conditionally stable for instantaneous stiffness hardening systems although it also possesses unconditional stability for linear elastic and any instantaneous stiffness softening systems. Due to the explicitness of each time step, the possibility of unconditional stability, and comparable accuracy, the proposed algorithm is very promising for a general structural dynamic problem, where only the low frequency responses are of interest since it consumes much less computational efforts when compared with explicit methods, such as the Newmark explicit method, and implicit methods, such as the constant average acceleration method.

В последнее время большую популярность приобретают численные методы исследования, как некая альтернатива дорогих и трудоемких экспериментальных методов. Современные вычислительные комплексы позволяют проводить анализ научно – технических задач в самых разных областях практической деятельности. В настоящей работе представлены результаты численного моделирования генерации электромагнитного поля, обусловленной движением твёрдого заряженного тела, в вычислительной среде ANSYS.CFX. Этим телом является шар, совершающий колебания в жидкости переменной плотности. Модельная постановка задачи позволяют лучше понять механизм генерации электромагнитного поля, который сопровождает движение твёрдого тела в проводящей среде. Рассматриваемое твердое тело моделируется набором 2D областей, формирующими его поверхность, при этом сетка движется по поверхности твёрдого тела в соответствии с решением уравнений динамики последнего. Решение уравнений прямолинейного движения выполняется дискретизацией по неявной схеме интегрирования Ньюмарка. При этом используется 2й порядок точности. Для расчета электромагнитного поля решалась система уравнений Максвелла, адаптированная в вычислительную структуру комплекса ANSYS. Recently, numerical research methods, as a kind of alternative to expensive and time-consuming experimental methods, have gained great popularity. Modern computer systems allow performing the analysis of scientific and technical problems in various fields of practical activity. This paper presents the results of a numerical simulation of electromagnetic field generation due to the motion of a solid charged entity in the ANSYS.CFX computing environment. This entity is a ball oscillating in a fluid of variable density. The model statement of the problem makes it possible to better understand the mechanism of electromagnetic field generation, which accompanies the motion of a solid in a conducting medium. The considered solid is modeled by a set of 2D sections forming its surface, while the grid moves along the surface of the solid in accordance with the solution of the dynamics equations of the latter. The solution of the equations of rectilinear motion is performed by discretization according to the implicit Newmark integration scheme. In this case, the second order of accuracy is used. To calculate the electromagnetic field, the Maxwell system of equations was used, adapted to the computational structure of the ANSYS complex.

A new time integration scheme is presented for solving the differential equation of motion with nonlinear stiffness. In this new implicit method, it is assumed that the acceleration varies quadratically within each time step. By increasing the order of acceleration, more terms of the Taylor series are used, which are expected to have responses with better accuracy than the classical methods. By considering this assumption and employing two parameters δ and α, a new family of unconditionally stable schemes is obtained. The order of accuracy, numerical dissipation, and numerical dispersion are used to measure the accuracy of the proposed method. Second order accuracy is achieved for all values of δ and α. The proposed method presents less dissipation at the lower modes in comparison with Newmark's average acceleration, Wilson-θ, and generalized-α methods. Moreover, this second order accurate method can control numerical damping in the higher modes. The numerical dispersion of the proposed method is compared with three unconditionally stable methods, namely, Newmark's average acceleration, Wilson-θ, and generalized-α methods. Furthermore, the overshooting effect of the proposed method is compared with these methods. By evaluating the computational time for analysis with similar time step duration, the proposed method is shown to be faster in comparison with the other methods.

The internal debonding effects on implicit transient responses of the shear deformable layered composite plate under the mechanical transverse (uniform and sinusoidal) loading are analyzed in this article. The physics of the laminated composite plate with internal debonding has been expressed mathematically via two kinds of midplane displacement functions based on Reddy's simple shear deformation kinematic theory. The geometrical nonlinearity of the debonded plate structure is estimated using total Lagrangian method. The time–displacement characteristics are evaluated numerically using the nonlinear finite element method (FEM). The governing equation of motion of the debonded laminated structure has been derived using the total Lagrangian method and solved numerically with the help of Newmark's time integration scheme in association with the direct iterative method. For the computation of output, a suitable matlab program is written by the use of the presently developed higher order nonlinear model. The consistency and the accuracy of the proposed complex numerical solutions have been established through the appropriate convergence and the comparison study. Finally, a series of numerical examples have been examined to address the influence of the size, the position, and the location of internal damage along with the material and geometrical parameter (modular ratio, side to thickness ratio, aspect ratio, and the boundary condition) on the nonlinear transient responses of delaminated composite plate and discussed in detail.

Introduction Curation-related discourses have become widespread. The growing public profile of curators, the emergence of new curation-related discourses and their proliferation beyond the confines of museums, particularly on social media, have led some to conclude that we now live in an age of curation (Buskirk cited in Synder). Curation is commonly understood in instrumentalist terms as the evaluation, selection and presentation of artefacts around a central theme or motif (see O’Neill; Synder). However, there is a growing academic interest in what underlies the shifting discourses and practices. Many are asking what do these changes mean (Martinon) now that “the curatorial turn” has positioned curation as a legitimate object of academic study (O’Neill). This article locates an exploration of the curatorial turn in journalism studies since 2010 within the shifting meanings of curation from antiquity to the digital age. It argues that the industry is facing a Foucauldian moment where the changing political economy of news and the proliferation of user-generated content on social media have disrupted the monopolies traditional news media held over the circulation of knowledge of current affairs and the power this gave them to shape public debate. The disruptions are profound, prompting a rethinking of journalism (Peters and Broersma; Schudson). However, debates have polarised between those who view news curation as symptomatic of the demise of journalism and others who see it as part of a wider revival of the profession, freed from monopolistic institutions to circulate a wider array of knowledge and viewpoints (see Picard). This article eschews such polarisations and instead draws on Robert Picard’s argument that journalism is in transition and that journalism, as a set of professional practices, is adapting to the age of curation but that those traditional news providers that fail to adapt will most likely decline. However, Picard’s approach does not address the definitional problem as to what distinguishes news curating from other journalistic practices when the commonly used instrumental definition can apply to editing. This article aims to negotiate this problem by addressing some of the conceptual ambiguities that arise from wholly instrumental notions of news curation. From “Cura” to the Curatorial Turn and the Age of Curation Modern instrumentalist definitions are necessary but not sufficient for an exploration of the curatorial turn in journalism. Tracing the meanings of curation over time facilitates an expansion of the instrumental to include metaphoric conceptualisations. The term originated in a Latin allegory about a mythological figure, personified as the “cura”, translated literally as care or concern, and who created human beings from the clay of the earth. Having created the human, the cura was charged by the gods with the lifelong care of the human (Reich) and at the same time became a symbol of curiosity and creativity (see Nowotny). “Curators” first emerged in Imperial Rome to denote a public officer charged with maintaining order and the emperor’s finances (Nowotny) but by the fourteenth century the meaning had shifted to that of religious officer charged with the care of souls (Gaskill). At this point the metaphorical associations of creativity and curiosity subsided. Six hundred years later souls had been replaced by artefacts valorised because of their contribution to human knowledge or as a testament to exceptional human creativity (Nowotny). Objects of curiosity and originality, as well as their creators, were reified and curation became the specialist practice of an expert custodian charged with the care and preservation of artefacts but relegated to the background to collect, evaluate and archive artefacts entrusted to the care of museums and to be preserved for future generations. Instrumentalist meanings thus dominated. From the 1960s discourses shifted again from the privileging of a “producer who actually creates the object in its materiality” to an entire set of actors (Bourdieu 261). These shifts were part of the changing political economy of museums, the growing prevalence of exhibitions and the emergence of mega-exhibitions hosted in global cities and capable of attracting massive audiences (see O’Neill). The curator was no longer seen merely as a custodian but able to add cultural value to artefacts when drawing individual items together into a collection, interpreting their relevance to a theme then re-presenting them through a story or visuals (see O’Neill). The verb “to curate”, which had first entered the English lexicon in the early 1900s but was used sporadically (Synder), proliferated from the 1960s in museum studies (Farquharson cited in O’Neill) as mega-exhibitions attracted publicity and the higher profile of curators attracted the attention of intellectuals prompting a curatorial turn in museum studies. The curatorial turn in museum studies from the 1980s marks the emergence of curation as a legitimate object of academic enquiry. O’Neill identified a “Foucauldian moment” in museum studies where shifting discourses signified challenges to, and disruptions of, traditional forms of knowledge-based power. Curation was no longer seen as a neutral activity of preservation, but one located within a contested political economy and invested with contradictions and complexities. Philosophers such as Martinon and Nowotny have highlighted the impossibility of separating the oversight of valuable artefacts from the processes by which these are selected, valorised and signified and what, at times, has been the controversial appropriation of creative outputs. Thus, a new critical approach emerged. Recently, curating-related discourses have expanded beyond the “rarefied” world of museum studies (Synder). Social media platforms have facilitated the proliferation of user-generated content offering a vast array of new artefacts. Information circulates widely and new discourses can challenge traditional bases of knowledge. Audiences now actively search for new material driven in part by curiosity and a growing distrust of the professions and establishments (see Holmberg). The boundaries between professionals and lay people are blurring and, some argue, knowledge is being democratized (see Ibrahim; Holmberg). However, as new information becomes voluminous, alternative truths, misinformation and false information compete for attention and there is a growing demand for the verification, selection and presentation of artefacts, that is online curation (Picard; Bakker). Thus, the appropriation of social media is disrupting traditional power relations but also offering new opportunities for new information-related practices. Journalism is facing its own Foucauldian moment. A Foucauldian Moment in Journalism Studies Journalism has been traditionally understood as capturing today’s happenings, verifying the facts of an event, then presenting these as a narrative that reporters update as news unfolds. News has been seen as the preserve of professionals trained to interview eyewitnesses or experts, to verify facts and to compile what they found into a compelling narrative (Hallin and Mancini). News-gathering was typically the work of an individual tasked with collecting stand-alone stories then passing them onto editors to evaluate, select, prioritise and collate these into a collection that formed a newspaper or news programme . This understanding of journalism emerged from the 1830s along with a type of news that was accessible, that large numbers of people wanted to read and that, consequently, attracted advertising making news profitable (Park). The idea that presumed trained journalists were best placed to produce news appeared first in the UK and USA then spread worldwide (Hallin and Mancini). At the same time as there was growing demand for news, space constraints restricted how much could be published and the high costs of production served as a barrier to entry first in print then later in broadcast media (Picard; Curran and Seaton). The large news organisations that employed these professionals were thus able to control the circulation of information and knowledge they generated and the editors that selected content were able, in part, to shape public debates (Picard; Habermas). Social media challenge the control traditional media have had over the production and dissemination of news since the mid-1800s. Practically every major global news story in 2010 and 2011 from natural disasters to uprisings was broken by ordinary people on social media (Bruns and Highfield). Twitter facilitates a steady stream of updates at an almost real-time speed that 24-hour news channels cannot match. Facebook, Instagram and blogs add commentary, context, visuals and personal stories to breaking news. Experts and official sources routinely post announcements on social media platforms enabling anyone to access much of the same source material that previously was the preserve of reporters. Investigations by bloggers have exposed abuses of power by companies and governments that journalists on traditional media have failed to (Wischnowski). Audiences and advertisers are migrating away from traditional newspapers to a range of different online platforms. News consumers now actively use search engines to find available information of interest and look for efficient ways of sifting through the proliferation of the useful and the dubious, the revelatory and the misleading or inaccurate (see Picard). That is, news organisations and the professional journalists they employ are increasingly operating in a hyper-competitive (see Picard) and hyper-sceptical environment. This paper posits that cumulatively these are disrupting the control news organisations have and journalism is facing a Foucauldian moment when shifting discourses signify a disturbance of the intellectual rules that shape who and what knowledge of news is produced and hence the power relations they sustain. Social media not only challenge the core news business of reporting, they also present new opportunities. Some traditional organisations have responded by adding new activities to their repertoire of practices. In 2011, the Guardian uploaded its entire database of the expense claims of British MPs onto its Website and invited readers to select, evaluate and comment on entries, a form of crowd-sourced curating. Andy Carvin, while at National Public Radio (NPR) built an international reputation from his curation of breaking news, opinion and commentary on Twitter as Syria became too dangerous for foreign correspondents to enter. New types of press agencies such as Storyful have emerged around a curatorial business model that aggregates information culled from social media and uses journalists to evaluate and repackage them as news stories that are sold onto traditional news media around the world (Guerrini). Research into the growing market for such skills in the Netherlands found more advertisements for “news curators” than for “traditional reporters” (Bakker). At the same time, organic and spontaneous curation can emerge out of Twitter and Facebook communities that is capable of challenging news reporting by traditional media (Lewis and Westlund). Curation has become a common refrain attracting the attention of academics. A Curatorial Turn in Journalism The curatorial turn in journalism studies is manifest in the growing academic attention to curation-related discourses and practices. A review of four academic journals in the field, Journalism, Journalism Studies, Journalism Practice, and Digital Journalism found the first mention of journalism and curation emerged in 2010 with references in nearly 40 articles by July 2015. The meta-analysis that follows draws on this corpus. The consensus is that traditional business models based on mass circulation and advertising are failing partly because of the proliferation of alternative sources of information and the migration of readers in search of it. While some of this alternative content is credible, much is dubious and the sheer volume of information makes it difficult to discern what to believe. It is unsurprising, then, that there is a growing demand for “new types and practices of curation and information vetting” that attest to “the veracity and accuracy of content” particularly of news (Picard 280). However, academics disagree on whether new information practices such as curation are replacing or supplementing traditional newsgathering. Some look for evidence of displacement in the expansion of job advertisements for news curators relative to those for traditional reporters (Bakker). Others look at how new and traditional practices co-exist in organisations like the BBC, Guardian and NPR, sometimes clashing and sometimes collaborating in the co-creation of content (McQuail cited in Fahy and Nisbet; Hermida and Thurman). The debate has polarised between whether these changes signify the “twilight years of journalism or a new dawn” (Picard). Optimists view the proliferation of alternative sources of information as breaking the control traditional organisations held over news production, exposing their ideological biases and disrupting their traditional knowledge-based power and practices (see Hermida; Siapera, Papadopoulou, and Archontakis; Compton and Benedetti). Others have focused on the loss of “traditional” permanent journalistic jobs (see Schwalbe, Silcock, and Candello; Spaulding) with the implication that traditional forms of professional practice are in demise. Picard rejects this polarisation, counter-arguing that much analysis implicitly conflates journalism as a practice with the news organisations that have traditionally hosted it. Journalists may or may not be located within a traditional media organisation and social media is offering numerous opportunities for them to operate independently and for new types of hybrid practices and organisations such as Storyful to emerge outside of traditional operations. Picard argues that making the most of the opportunities social media presents is revitalising the profession offering a new dawn but that those traditional organisations that fail to adapt to the new media landscape and new practices are in their twilight years and likely to decline. These divergences, he argues, highlight a profession and industry in transition from an old order to a new one (Picard). This notion of journalism in transition usefully negotiates confusion over what curation in the social media age means for news providers but it does not address the uncertainty as to where it sits in relation to journalism. Futuristic accounts predict that journalists will become “managers of content rather than simply sourcing one story next to another” and that roles will shift from reporting to curation (Montgomery cited in Bakker; see Fahy and Nisbet). Others insist curators are not journalists but “information workers” or “gatecheckers” (McQuail 2013 cited in Bakker; Schwalbe, Silcock, and Candello) thereby differentiating the professional from the manual worker and reinforcing the historic elitism of the professions by implying curation is a lesser practice. However, such demarcation is problematic in that arguably both journalist and news curator can be seen as information workers and the instrumental definition outlined at the beginning of this article is as relevant to curation as it is to news editing. It is therefore necessary to revisit commonly used definitions (see Bakker; Guerrini; Synder). The literature broadly defines content creation, including news reporting, as the generation of original content that is distinguishable from aggregation and curation, both of which entail working with existing material. News aggregation is the automated use of computer algorithms to find and collect existing content relevant to a specified subject followed by the generation of a list or image gallery (Bakker; Synder). While aggregators may help with the collection component of news curation, the practices differ in their relation to technology. Apart from the upfront human design of the original algorithm, aggregation is wholly machine-driven while modern news curation adds human intervention to the technological processes of aggregation (Bakker). This intervention is conscious rather than automated, active rather than passive. It brings to bear human knowledge, expertise and interpretation to verify and evaluate content, filter and select artefacts based on their perceived quality and relevance for a particular topic or theme then re-present them in an accessible form as a narrative or infographics or both. While it does not involve the generation of original news content in the way news reporting does, curation is more than the collation of information. It can also involve the re-presenting of it in imaginative ways, the re-formulating of existing content in new configurations. In this sense, curation can constitute a form of creativity increasingly common in the social media age, that of re-mixing and re-imagining of existing material to create something novel (Navas and Gallagher). The distinction, therefore, between content creation and content curation lies primarily in the relation to original material and not the assumed presence or otherwise of creativity. In addition, curation outputs need not stand apart from news reports. They can serve to contextualize news in ways that short reports cannot while the latter provides original content to sit alongside curated materials. Thus the two types of news-related practices can complement rather than compete with each other. While this addresses the relation between reporting and curation, it does not clarify the relation between curating and editing. Bakker eludes to this when he argues curating also involves “editing … enriching or combining content from different sources” (599). But teasing out the distinctions is tricky because editing encompasses a wide range of sub-specialisations and divergent duties. Broadly speaking, editors are “newsrooms professionals … with decision-making authority over content and structure” who evaluate, verify and select information so are “quality controllers” in newsrooms (Stepp). This conceptualization overlaps with the instrumentalist definition of curation and while the broad type of skills and tasks involved are similar, the two are not synonymous. Editors tends to be relatively experienced professionals who have worked up the newsroom ranks whereas news curators are often new entrants ultimately answerable to editors. Furthermore, curation in the social media age involves voluminous material that curators sift through as part of first level content collection and it involves ever more complex verification processes as digital technologies make it increasingly easy to alter and falsify information and images. The quality control role of curators may also involve in-house specialists or junior staff working with external experts in a particular region or specialisation (Fahy and Nisbett). Some of job advertisements suggest a growing demand for specialist curatorial skills and position these alongside other newsroom professionals (Bakker). Whether this means they are journalists is still open to question. Conclusion This article has presented a more expansive conceptualisation of news curation than is commonly used in journalism studies, by including both the instrumental and the symbolic dimensions of a proliferating practice. It also sought to avoid confining this wider conceptualisation within unhelpful polarisations as to whether news curation is symbolic of a wider demise or revival of journalism by distinguishing the profession from the organisation in which it operates. The article was then free to negotiate the conceptual ambiguity surrounding the often taken-for-granted instrumental meanings of curation. It argues that what distinguishes news curation from traditional newsgathering is the relationship to original content. While the reporter generates the journalistic equivalent of original content in the form of news, the imaginative curator re-mixes and re-presents existing content in potentially novel ways. This has faint echoes of the mythological cura creating something new from the existing clay. The other conceptual ambiguity negotiated was in the definitional overlaps between curating and editing. On the one hand, this questions the appropriateness of reducing the news curator to the status of an “information worker”, a manual labourer rather than a professional. On the other hand, it positions news curators as one of many types of newsroom professionals. 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