Simulation and automation of calculations of buildings (structures) on seismic effects

In many countries there are standards as one-dimensional, console systems for calculations of buildings, which stay in contradiction with the experience of destructive earthquakes. This scientific work offers an explanation for the transfer from one-dimensional to three-dimensional models of different complexity in standards. Discretely-continuous and discrete models of buildings have already been worked out as unified three-dimensional systems with floors deforming in their own plane.

We have considered models of seismic effects, which take into account the effect of the running seismic wave under the ground and the effect of non-uniformity of oscillation field along an extended building or a structure. We pointed out paradoxes in calculations while using three-dimensional models of buildings and “zero-dimensional” (normative) models of soil seismic effects on their grounds. In relation to this problem, we have executed the correction of the formula for determination of seismic forces.

Variational methods of making up the solving equations have been developed for calculation of oscillations of buildings as dynamic systems of large dimension. The structural analysis of buildings, of hydraulic structures, of bridges and of ship hulls has expediently proved to choose own vectors of rigidity matrixes separated out of a three-dimensional object of flat elements as possible displacements. It is the key to “rolling-up” extensive solving equations with thousands of the unknowns and “compressing” the three-dimensional object in one or two directions.

In order to simplify the calculations, we use so-called principle of partial symmetry, connected with mechanisms of deformation of cross- or longitudinal-sections of a three-dimensional construction. The principle can be considered as transformations leaving mathematical objects (tensors) invariant. In mathematical plan the symmetry causes break-up of solving equations into the independent blocks.

In an effort to adjust sequentially solutions, a hierarchical chain of mathematical simulation models of different levels was built, in which own vectors of flat elements are considered as hypotheses of deformation. We have developed program complex “PRIS” to automize calculations of buildings by three-dimensional models. The spectral methods of calculations are generalized for universal three-dimensional models of buildings to use standards of different countries in the developed program complex.     

CAE system in mechanical engineering

Two interactive CAE systems in mechanical engineering were developed. One is a general purpose system for structural design. All stages of design from the beninning of structural analysis to the last stage of strength evaluation can be treated so that optimal structures can be obtained by using this system with changing shapes and dimensions of the structures.

The other one is limited for turbomachinery design. But this includes not only analysis and simulation programs but also design programs and accumulated data for the products, etc.

This paper explains these systems and some element programs which support the system.     

Concepts and implementation of parallel finite element analysis

The design of complex engineering systems such as advanced aircraft structures and offshore platforms requires continually increasing levels of detail in supporting analysis. The finite element method is widely used as a computational method with which to model physical systems in various engineering problems. For detailed analyses of complex designs, structural models composed of several thousands of degrees of freedom are no longer uncommon. Such design activities require large order finite element and/or finite difference models and excessive computation demands in both calculation speed and information management. The computer simulation of the nonlinear dynamic response of structures and the implementation of parallel FEM systems on a high speed multiprocessor have received considerable attention in recent years. The driving forces of these activities included the reliable simulation of automotive and aircraft crash phenomena, and the increased performance of computers. Most existing major structural analysis software systems were designed 10–20 years ago and have been optimized for current sequential computers. Such systems often are not well structured to take maximum advantage of the recent and continuing revolution in parallel vector computing capabilities. These parallel vector computer architectures not only occur in the form of large supercomputers, but are now also occurring for minicomputers and even engineering workstations. To benefit from advances in parallel computers, software must be developed which takes maximum advantage of the parallel processing feature.     

Model-free data interpretation for continuous monitoring of complex structures

Civil engineering structures are difficult to model accurately and this challenge is compounded when structures are built in uncertain environments. As consequence, their real behavior is hard to predict; such difficulties have important effects on the reliability of damage detection. Such situations encourage the enhancement of traditional approximate structural assessments through in-service measurements and interpretation of monitoring data. While some proposals have recently been made, in general, no current methodology for detection of anomalous behavior from measurement data can be reliably applied to complex structures in practical situations.This paper presents two new methodologies for model-free data interpretation to identify and localize anomalous behavior in civil engineering structures. Two statistical methods (i) moving principal component analysis and (ii) moving correlation analysis have been demonstrated to be useful for damage detection during continuous static monitoring of civil structures.The algorithms are designed to learn characteristics of time series generated by sensor data during a period called the initialization phase where the structure is assumed to behave normally. This phase subsequently helps identify those behaviors which can be classified as anomalous. In this way the new methodologies can effectively identify anomalous behaviors without explicit (and costly) knowledge of structural characteristics such as geometry and models of behavior. The methodologies have been tested on numerically simulated elements with sensors at a range of damage severities. A comparative study with wavelet and other statistical analyses demonstrates superior performance for identifying the presence of damage.     

基于MAR 的工程制图助学系统研究

在工程制图课程中根据二维图纸来构思三维形状,对于初学者来说有相当大的难 度。针对传统基于PC 端工程制图的多媒体辅助教学方式在交互性和易用性上的不足,研究基 于移动增强现实的工程制图助学系统。采用无标记识别技术实现工程图样与三维数字化模型的 自然交互,并在此基础上开发了一个功能齐全的助学APP,使用者可以通过手机摄像头扫描识 别二维工程图,在屏幕上叠加显示三维模型以及其他相关教学资源,用户可实时完成模型缩放、 旋转等操作,并且可对复杂的工程装配体模型进行拆卸和组装。实验结果表明,该系统不仅便 于学生自主学习,而且在一定程度上改善了工程制图课程的教学环境。     

An edge-based data structure for two-dimensional finite element analysis

The introduction of engineering work stations has made it possible for an analyst to describe a two-dimensional finite element model and view its response in a real-time, interactive graphical environment. This interactive environment puts severe performance restrictions on finite element programs. The programs must be able to respond to an analyst's request in a reasonable amount of time. The traditional finite element data structures cannot provide the required performance. This paper introduces a new application of an existing data structure, the winged-edge, which can provide the required performance. The winged-edge data structure is described, with particular emphasis given to its use for finite element analysis. The implementation of the data structure in a fracture analysis program is discussed and a number of examples of its use are presented.     

Isothermal phase change model for freezing and thawing soils I: Development

A model of phase change in freezing and thawing soils is developed for cold regions engineering problems which require two-dimensional analysis of the thermal regime of soils. Such problems include complex boundary conditions such as atmosphere-ground surface thermal interaction and snowpack-insulation. Other concerns include complex soil conditions such as the presence of a peaty muskeg or tundra-like soil which may provide thermal insulation for underlying ice-rich mineral soil. Although several models have been developed to predict temperatures in freezing and thawing soils, oftentimes the key question is simply whether or not the soil is frozen since soil structural properties are significantly influenced by the soil-water state of phase. In this paper, a simple two-dimensional model is developed for use in cold regions engineering studies.     

The use of computers in preliminary structural design of buildings

This paper presents a case study of the use of computers for the preliminary structural design of a multi-story office building.First, preliminary structural design is discussed in relation to the entire building design process. Then, specifie computer applications are discussed for the following design activities: system selection, definition of structural elements, modeling of structural systems for analysis, and design of individual elements. Instead of isolated computer programs, this approach to computer usage emphasizes a system capable of creating and maintaining a structural data base for the life of a project.     

Hyperbolic trees for efficient routing computation

Complex system theory is increasingly applied to develop control protocols for distributed computational and networking resources. The paper deals with the important subproblem of finding complex connected structures having excellent navigability properties using limited computational resources. Recently, the two-dimensional hyperbolic space turned out to be an efficient geometry for generative models of complex networks. The networks generated using the hyperbolic metric space share their basic structural properties (like small diameter or scale-free degree distribution) with several real networks. In the paper, a new model is proposed for generating navigation trees for complex networks embedded in the two-dimensional hyperbolic plane. The generative model is not based on known hyperbolic network models: the trees are not inferred from the existing links of any network; they are generated from scratch instead and based purely on the hyperbolic coordinates of nodes. We show that these hyperbolic trees have scale-free degree distributions and are present to a large extent both in synthetic hyperbolic complex networks and real ones (Internet autonomous system topology, US flight network) embedded in the hyperbolic plane. As the main result, we show that routing on the generated hyperbolic trees is optimal in terms of total memory usage of forwarding tables.

     

Curved girder bridge analysis

A Fourier Series Slope-Deflection Technique has been developed as a means of analyzing curved girder bridge systems, which may contain orthotropic decks. The technique incorporates both pure and warping torsional effects as well as bending effects. Girder deflections and internal forces are determined at any location along the respective girders. The resulting forces include bending moment, shear, pure torsion, warping torsion, and bimoment.

The entire slope-deflection analyses has been programmed for use on an IBM 7094 computer, FORTRAN IV language. The three programs for a (1) single span analysis, (2) two-span continuous structure, and (3) three-span continuous structure may be obtained from the authors.     

Processing three-dimensional finite element assemblies and solutions

The ideas previously proposed in this journal for preprocessing three-dimensional solid finite element structures and for postprocessing finite element analyses of these structures are extended and given the flexibility required for practical use as an engineering tool.     

Efficient binary transfer of pointer structures

This paper presents a pair of algorithms for output and input of pointer structures in binary format. Both algorithms operate in linear space and time. They have been inspired by copying garbage collection algorithms, and make similar assumptions about the representations of pointer structures. In real programs, the transfer of entire pointer structures is often inappropriate. The algorithms are extended to transfer partitions of a pointer structure lazily: the receiver requests partitions when it needs them. A remote procedure call mechanism is presented that uses the binary transfer algorithms for communicating arguments and results. A use of this as an enabling mechanism in the implementation of a software engineering environment is discussed.     

Analysis and design of cable structure S

As a class, suspension structures are generally more flexible than framed or trussed structures. A consequency of this flexibility is that factors often need be considered when engineering cable structures which may be neglected when designing more conventional structural systems. Among these factors are: difficulties associated with mathematically defining the suspension structure's initial shape and the member forces corresponding to that state, the nonlinear relationship between changes of loading and displacement, and the susceptibility of some types of cable structures to wind-induced oscillations.

In the paper, cable structures are classified and examples of some types are illustrated together with a discussion of their advantages and disadvantages. The problem of establishing the initial shape of the structure is discussed. Some techniques for computing the displacements of suspension structures resulting from changes in static loading, considering the geometrical nonlinearity, are described. A procedure for determining the displacements of stiffened and unstiffened cable three-dimensional structures is outlined that is suitable for computer solution. Results of numerical studies made utilizing this technique are presented.     

Bifurcation, pre- and post-buckling analysis of frame structures

A procedure is developed for investigating the stability of complex structures that consist of an assembly of stiffened rectangular panels and three-dimensional beam elements. Such panels often form one of the basic structural components of an aircraft or ship structure. In the present study, the stiffeners are treated as beam elements, and the panels between them as thin rectangular plate elements, which may be subject to membrane and/or bending and twisting actions.

The main objective of the study is the determination of the critical buckling loads and the generation of the complete force-deformation behavior of such structures within a specified load range, based on the use of a computer program developed for this purpose. The present formulation can trace through the postbuckling or post limit behavior whether it is of an ascending or descending type. A limit load extrapolation technique is automatically initiated within the computer program, when the stability analysis of an imperfect or laterally loaded structure is being carried out.

The general approach to the solution of the problem is based on the finite element method and incremental numerical solution techniques. Initially, nonlinear strain-displacement relations together with the assumed displacement functions are utilized to generate the geometric stiffness matrices for the beam and plate elements. Based on energy methods and variational principles, the basic expressions governing the behavior of the structure are then obtained. In the incremental solution process, the stiffness properties of the structure are continuously updated in order to properly account for large changes in the geometry of the structure.

The computer program developed during the course of this study is referred at as GWU-SAP, or the George Washington University Stability Analysis Program.     

Monitoring cache behavior on parallel SMP architectures and related programming tools

This paper describes the ideas and developments of the project EP-CACHE. Within this project new methods and tools are developed to improve the analysis and the optimization of programs for cache architectures, especially for SMP clusters. The tool set comprises the semi-automatic instrumentation of user programs, the monitoring of the cache behavior, the visualization of the measured data, and optimization techniques for improving the user program for better cache usage.

As current hardware performance counters do not give sufficient user relevant information, new hardware monitors are designed that provide more detailed information about the cache utilization related to the data structures and code blocks in the user program. The expense of the hardware and software realization will be assessed to minimize the risk of a real implementation of the investigated monitors. The usefulness of the hardware monitors is evaluated by a cache simulator.     

Nonlinear free vibration of fixed off-shore framed structures

The dynamical behavior of fixed off-shore framed structures is studied using the Wittrick-Williams algorithm to solve the nonlinear eigenvalue problem. The effects of shear deformation and rotary inertia as well as axial static loading are considered in this study of nonlinear free vibration.

The members are assumed to be rigidly connected and the added water mass is assumed equal to the mass of the water displaced. The structural modeling is based on a two-dimensional representation of the three-dimensional tower assuming a constant dimension equal to the base length perpendicular to the plane. The distributed masses of the members in the plane of the frame are computed by summing up the structural mass, the mass of the water contained in the tube, and the mass of the water displaced. The member masses in the plane perpendicular to the frame are assumed to be lumped at the horizontal cross-brace levels.

The results of the study indicate that while the first two frequencies obtained from the nonlinear and linear eigenvalue solutions agree closely, the effect of nonlinear eigenvalue solution is significant for the higher frequencies. The results also highlight the significant effects of the axial static force in the dynamic tangent stiffness matrix in the free vibration study of the off-shore structure. Fields for further research include (i) soil-structure interaction studies for gravity off-shore structures, buried pipelines, and (ii) nuclear power plant structures.     

Solid-to-shell transition elements for the computation of interlaminar stresses

This paper presents an accurate and practical technique for coupling shell element models to three-dimensional continuum finite element models. The compatibility between these two types of formulations is enforced by degenerating a continuum element through kinematic constraints compatible with shell deformations. Two formulations of two-dimensional/three-dimensional transition elements are presented. The first and simplest formulation is based on the Mindlin-Reissner plate assumptions, and is found to perform well in a variety of problems involving the analysis of geometrically linear/non-linear laminated structures. The second formulation is based on a higher-order shell theory that allows stretching in the through-the-thickness direction. This additional freedom virtually eliminates the interlaminar normal stress boundary layer that can form in lower-order transition elements. Finally, the coupling of two-dimensional to three-dimensional subdomains is enriched with the use of an interface element, which can be used in conjunction with either transition formulation. The interface element improves the efficiency of the solid-to-shell transition modeling scheme by allowing the independent selection of optimal mesh sizes in the shell and the three-dimensional regions of the model.