INACOF—A computer program for the inelastic analysis of reinforced concrete framed structures

The paper presents a general-purpose computer program for the inelastic analysis of reinforced concrete frames based on the method of imposed rotations. The program is capable of calculating the response of the structure to a given loading and also capable of performing collapse load analysis of the given structure. The program has been tested for a variety of problems and has been found to be extremely efficient compared to the other existing routines with much more limited capabilities. Complete listing and information for using the program has been presented.     

Damped second-order Rayleigh-Timoshenko beam vibration in space—an exact complex dynamic member stiffness matrix

A uniform linear beam in a uniform linear ambient medium is studied. The beam performs stationary harmonic damped nonsynchronous space vibration in simultaneous tension, torsion, bending and shear in the presence of a large static axial load. Hysteretic and viscous dampings of the beam material and ambient medium are considered. Generalized complex Kolou?ek functions are derived. A 12 × 12 complex symmetric stiffness matrix is established for a supported beam member excited at its ends by prescribed harmonic translations and rotations which have the same frequency but may be out of phase. This matrix allows for an exact analysis of nonproportionally damped built-up beam structures, thus avoiding assumed mode shapes and lumped or consistent masses. A general notation is suggested. Numerical examples are given, including applications of the computer program SFVIBAT-DAMP.     

A spline wavelets element method for frame structures vibration

A spline wavelets element method that combines the versatility of the finite element method with the accuracy of spline functions approximation and the multiresolution strategy of wavelets is proposed for frame structures vibration analysis. Instead of exploring orthogonal wavelets for specific differential operators, the spline wavelets are applied directly in finite element implementation for general differential operators. Although lacking orthogonality, the two-scale relations of spline functions and its corresponding wavelets from multiresolution analysis are employed to facilitate the elemental matrices manipulation by constructing two transform matrices under the constraint of finite domain of elements. In the actual formulation, the segmental approach for spline functions is provided to simplify the computation, much as conventional finite element procedure does. The assembled system matrices at any resolution level are reusable for the furthur finer resolution improvement. The local approximation and hiararchy merits make the approach competitive especially for higher mode vibration analysis. Some examples are studied as verification and demonstration of the approach.     

A lanczos-based technique for exact vibration analysis of skeletal structures

This paper presents and discusses a Lanczos-based eigensolution technique for evaluating the natural frequencies and modes from frequency-dependent eigenproblems in structural dynamics. The new solution technique is used in conjunction with a mixed finite element modelling procedure which utilizes both the polynomial and frequency-dependent displacement fields in formulating the system matrices. The method is well suited to the solution of large-scale problems. The new solution methodology presented here is based on the ability to evaluate a specific set of parameterized non-linear eigenvalue curves at given values of the parameter through an implicitly restarted Lanczos technique. Numerical examples illustrate that the implicitly restarted Lanczos method with secant interpolation accurately evaluates the exact natural frequencies and modes of the non-linear eigenproblem and verifies that the new eigensolution technique coupled with the mixed finite element modelling procedure is more accurate than the conventional finite element models. In addition, the eigenvalue technique presented here is shown to be far more computationally efficient on large-scale problems than the determinant search techniques traditionally employed for solving exact vibration problems.     

RADS — a computer package for refrigeration analysis, design and simulation

A commercially available computer package for refrigeration analysis, design and simulation is described. Its main applications are heat load determination, multi-stage compression plant layout design, and simulation of the interactions between refrigerant plant, applications and control systems.     

An energy‐momentum method for in‐plane geometrically exact Euler–Bernoulli beam dynamics

Nonlinear geometrically exact rod dynamics is of great interest in many areas of engineering. In recent years, the research was focused towards Timoshenko‐type rod theories where shearing is of importance. However, in many general model of mechanisms and spatial deformations, it is desirable to have a displacement‐only formulation, which brings us back to the classical Bernoulli beam. While it is well known for linear analysis, the Bernoulli beam is not as common in geometrically exact models of dynamics, especially when we want to incorporate the rotational inertia into the model. This paper is about the development of an energy‐momentum integration scheme for the geometrically exact Bernoulli‐type rod. We will show that the task is achievable and devise a general framework to do so. Copyright © 2014 John Wiley & Sons, Ltd.     

平面钢框架在撞击荷载作用下的抗连续倒塌分析

各种自然灾害和人为因素都可能造成结构连续倒塌,抗连续倒塌研究经常抛开引起倒塌破坏的原因,直接拆除关键柱,研究剩余结构的抗倒塌性能.该研究以平面框架受撞击荷载为例分析具体灾害对框架结构抗倒塌性能的影响,提出一种撞击力简化模型,分析结构体系对撞击力的激励反应,并将撞击拆柱法模拟结果与传统直接拆柱法结果对比,分析两种方法对结...     

Finite-element time-domain modelling of plane wave scattering by a periodic structure using an exact boundary condition

A two-dimensional singly-periodic structure, at plane wave oblique incidence, is modelled using the finite-element time-domain method. Over the non-periodic boundaries of the computational domain, an exact Floquet modal absorbing boundary condition is developed, in detail, for the finite element method in the time domain. The proposed formulation is validated by comparing its results with that of the finite-element frequency-domain method and with independently obtained published results. Very accurate numerical results, over a wide frequency range and incident angle range, are obtained for both transverse electric and transverse magnetic polarised plane wave illuminations     

Coupled vibrations of beams—an exact dynamic element stiffness matrix

A uniform linearly elastic beam element with non-coinciding centres of geometry, shear and mass is studied under stationary harmonic end excitation. The Euler-Bernoulli-Saint Venant theory is applied. Thus the effect of warping is not taken into account. The frequency-dependent 12 × 12 element stiffness matrix is established by use of an exact method. The translational and rotational displacement functions are represented as sums (real) of complex exponential terms where the complex exponents are numerically found. Built-up structures containing beam elements of the described type can be analysed with ease and certainty using existing library subroutines.     

On a method for vibration analysis of viscous compressible fluid–structure systems

A fluid–structure interaction formulation for viscous compressible fluid is under consideration. The formulation involves finite element approximation of linearized Navier–Stokes equations and response determination made by means of modal superposition analysis. Standard and simplified schemes of the viscous compressible fluid–structure interaction problem solution are developed. The schemes are based on the frequency condensation method of a complex eigenvalue problem solving. Free and forced oscillations of several fluid–structure systems are studied by the standard and simplified schemes. The analysis of the results obtained shows that the simplified scheme provides a saving of 90% of the computational time required to define oscillation of the structure with viscous compressible fluid in the lowest frequency range. A certain influence of the fluid viscosity on the transient response of the fluid–structure system is also demonstrated. Copyright © 2004 John Wiley & Sons, Ltd.     

A computer program for repetitive strain gauge rosette analysis

A system is described with which the signals from a strain gauge rosette can be used to compute principal stresses and their orientation, the results being plotted on a VDU screen and updated continuously.     

密肋复合墙板支撑框架结构自振周期计算方法

密肋复合墙板支撑框架结构是由框架与其内部嵌入的密肋复合墙板组成的一种双重抗震结构,框架内部嵌入复合墙板所组成的受力构件,其变形特征不同于普通框架和剪力墙,由此导致结构的自振周期计算方法不能直接按照一般框架-剪力墙结构进行计算。本文以Timoshenko双变量梁理论及协同工作模型为基础,建立了复合墙板支撑框架结构的频率方程,结合边界条件导出了结构的自振周期计算公式,并给出了基本自振周期的近似计算方法。算例分析表明：复合墙板支撑框架结构自振周期受复合板抗剪刚度影响较大,且影响随着振型的增加而增大,高振型时复合墙板剪切变形的影响不可忽略;采用似计算方法计算基本自振周期的误差不大,可以满足工程计算精度要求。     

基于动力刚度法的体外预应力梁自振频率分析

用预应力梁-杆组合结构模拟体外预应力梁,以体外预应力简支梁为例,建立了预应力梁杆单元动力刚度矩阵。采用动力刚度法,进一步推导出预应力梁-杆组合结构的整体动力刚度矩阵,利用Williams-Wittrick算法求解频率。本文以理论推导为基础,引入了动力刚度法。最后通过算例,讨论了各种因素对梁横向的振动特性的影响,并与试验值比较。计算结果表明:动力刚度法能够精确有效的求解体外预应力混凝土梁的横向振动问题。     

A multiharmonic method for non-linear vibration analysis

A multiharmonic method for analysis of non-linear dynamic systems submitted to periodic loa conditions is presented. The approach is based on a systematic use of the fast Fourier transform. The e linearization of the resulting equations in the frequency domain allows to obtain full quadratic converg rate.     

A generalized computer program for analysis of mixture refrigeration cycles

The growing interest in non-azeotropic refrigerant mixtures for heat pumps and appliances has led to the need for a method of analysing the refrigeration cycle properties of such mixtures. Thermodynamic property tables are not sufficient, because they give no information about the two-phase region, where temperature and vapour and liquid compositions are not constant at constant pressure. This paper describes the computer program CYCLE, which can perform thermodynamic property calculations for subcooled, two-phase, and superheated non-azeotropic mixtures and can analyse a simple refrigerating cycle.     

基于有限元的异步电机电磁振动分析

电机的电磁振动是电机电磁场与机械结构耦合的结果,要研究电机的电磁振动,需要将电机的电磁场和结构振动分析结合起来。通过有限元软件,采用一种弱磁-固耦合的方法,对异步电机的电磁振动特性进行分析。首先利用ANSOFT有限元软件建立异步电机的二维有限元模型,计算电机的瞬态电磁场,得到电机在给定转速稳态运行状态下的磁场分布和作用在定子上时变的电磁力;其次用ANSYS有限元软件建立异步电机结构的三维有限元模型,将ANSOFT软件得到的时变电磁力进行频谱分析并校正,然后施加到电机上,计算出电机结构的电磁振动响应。基于对电机电磁振动特性的分析,可以对电机的电磁参数和结构进行改进和优化设计,以降低电机的电磁振动     

Experimental analysis of vibration characteristics of an edge- cracked composite plate by ESPI method

In this paper, the amplitude fluctuation (AF) electronic speckle pattern interferometry (ESPI) method was adopted to investigate the vibration characteristics of a composite plate containing an edge crack. The change of the modal shapes was discussed. In addition, the stress intensity factors (SIFs) induced by the resonant vibration were evaluated. This revised version was published online in August 2006 with corrections to the Cover Date.     

Numerical and exact models for free vibration analysis of cylindrical and spherical shell panels

The present paper shows a comparison between classical two-dimensional (2D) and three-dimensional (3D) finite elements (FEs), classical and refined 2D generalized differential quadrature (GDQ) methods and an exact three-dimensional solution. A free vibration analysis of one-layered and multilayered isotropic, composite and sandwich cylindrical and spherical shell panels is made. Low and high order frequencies are analyzed for thick and thin simply supported structures. Vibration modes are investigated to make a comparison between results obtained via the FE and GDQ methods (numerical solutions) and those obtained by means of the exact three-dimensional solution. The 3D exact solution is based on the differential equations of equilibrium written in general orthogonal curvilinear coordinates. This exact method is based on a layer-wise approach, the continuity of displacements and transverse shear/normal stresses is imposed at the interfaces between the layers of the structure. The geometry for shells is considered without any simplifications. The 3D and 2D finite element results are obtained by means of a well-known commercial FE code. Classical and refined 2D GDQ models are based on a generalized unified approach which considers both equivalent single layer and layer-wise theories. The differences between 2D and 3D FE solutions, classical and refined 2D GDQ models and 3D exact solutions depend on several parameters. These include the considered mode, the order of frequency, the thickness ratio of the structure, the geometry, the embedded material and the lamination sequence.