长时间不用请先看介绍.doc

现在很多研究生学习OpenSEES这个程序，非常地火。OpenSEES是美国伯克利大学又一个成功的程序。正确的简写是OpenSEES，pen是小写的，呵呵。OpenSEES我也学得不好，但有网友要求我写一个简单的操作过程，我觉得应没多大问题，但是有个要求，请高手不要拍砖！献丑了。一般在我的博客可以下载到OpenSEES，网址是：/article.asp?id=21下载下来就以下几个文件，有范例，程序及说明书，这几个不到30MB的程序就可以完成非线性分析，是不是很神奇呢？（1）安装文件：OpenSEES要安装的文件只有一个，就是ActiveTcl-win32-ix86-99631.exe。双击它进行安装，不断地按NEXT就可以装完了，如图所示。（2）打开OpenSEES：OpenSEES.exe文件是不需要安装的，它是一个基于tcl的Dos窗口程序，双击打开，如图所示。不像现在的商业软件，一打开就是图形界面，这一点很多研究生接受不了，但对于早期接触有限元或电脑的人一点都不陌生。如以前的3DS，AutoCAD的第一个版本就是Dos程序，Abaqus 1.0与Sap4都是Dos程序，就是通过如下窗口输入命令流的。当然，学习OpenSEES的人不需要一个个字打命令流进去，这个容易出错，我们可以学习Ansys做法，把ADPL写到一个文本文件然后Load进去。正是这样，以下的方法就是：先写tcl文件，再Load进OpenSEES做计算。（3）创建OpenSEES工作目录：由于OpenSEES的程序非常小，不到5MB，可以在电脑里拖来拖去，我们可以创建一个新的文件夹，只放一个OpenSEES.exe，如下较长所示。再创建一个空的文本文件(txt)，右键创建就可以了。改名为test.tcl，然后用文本编辑器打开，文本编辑器，我建议采用UltraEdit，速度快且功能多。（4）编写一个简单的OpenSEES的tcl脚本：编写tcl脚本，需要打开OpenSEES的帮助手册，一步步按照手册来建模。所谓的建模，就是打命令流。帮助文件打开后如图所示。里面的建模命令都在这里面，点击后可以看到所有的步骤，从系统设置结点质量材料截面单元支座荷载分析工况分析参数分析，全过程。以下我写一个简单的tcl文件，一边解说。字体太小看不清，可以下载代码：点击下载此文件字体太小看不清，可以下载代码：点击下载此文件建模的内容是建一个柱子，一个侧向位移推它，Push-Over，得到基底剪力与顶部位移的曲线。模型的示意图如图所示,纤维截面大体如下图所示。分析完成会得到两个数据结果文件，也就是Recorder记录的内容，如下。recorder Node -file DFree.out -load -node 2 -dof 1 2 3 disp;# 记录顶点2的位移 1,2,3表示三个方向的平动自由度recorder Node -file DFIX.out -load -node 1 -dof 1 2 3 reaction;# 记录底点1的反力 1,2,3表示三个方向的平动自由度（5）结果后处理：打开两个结果文件，发现记录是按列记录，如DFree.out的文本，第一列是荷载倍数，第二至第四列是位移UX,UY,UZ，我们将它们复制到excel表格，分列一下，得到如下图所示的数据，将第一列的荷载倍数与UX的水平位移画图，就可以得到最简单的Push-Over曲线了，如下图所示。（6）学习建议：多看一些关于非线性有限元与宏观单元理论的书与论文；多动手做一些小算例，练习一下OpenSEES的操作；更复杂的模型需要编程实现，尝试掌握编程语言；IntroductionModern earthquake engineering utilizes modeling and simulation to understand the behavior and performance of systems during earthquakes. With the support of the National Science Foundation, the Pacific Earthquake Engineering Research Center (PEER) has developed the Open System for Earthquake Engineering Simulation, OpenSees for short, as a software platform for research and application of simulation for structural and geotechnical systems. The OpenSees software framework uses object-oriented methodologies to maximize modularity and extensibility for implementing models for behavior, solution methods, and data processing and communication procedures. The framework is a set of inter-related classes, such as domains (data structures), models, elements (which are hierarchical), solution algorithms, integrators, equation solvers, and databases. The classes are as independent as possible, which allows great flexibility in combining modules to solve simulation problems for buildings and bridges, including soil and soil-structure-foundation interaction, and most recently including reliability computational modules. The open source software is managed and made available to users and developers through the OpenSees website at.The software architecture and open-source approach for OpenSees provide many benefits to users interested in advanced simulation of structural and geotechnical systems with realistic models of nonlinear behavior. First, the modeling approach is very flexible in that allows selection and various combinations of a number of different element formulations and material formulations, along with different approximations of kinematics to account for large-displacements and P-D effects. As an open-source project, developers and researchers are using the extensible features of the software architecture to add additional capability. A second advantage is that there is a wide range of solution procedures and algorithms that the user can adapt to solve difficult nonlinear problems for static and dynamic loads. Another feature is that OpenSees has a fully programmable scripting language for defining models, solution procedures, and post-processing that can provide simple problem solving capability, as illustrated in this manual, or very sophisticated modeling and parameters studies of large, complex systems. Finally, OpenSees provides a flexible interface to computer resources, storage and databases, and network communication to take advantage of high-end computing systems. Structural and geotechnical models can be analyzed from desktop PCs to parallel computers within OpenSees.As an advanced platform for computational simulation, OpenSees provides an important resource for the National Science Foundation-sponsored George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES), and it has been adopted byNEESgridSystem Integration project as the NEES simulation component. The NEESgrid decision to utilize OpenSees and adapt it to interface with other NEESgrid resources provides an important capability for NEES researchers and users. The modular design of OpenSees means that it can be customized for the integrating physical and computation simulation through data repositories, visualization, and hybrid control for advanced experimental methods, all of which meet important NEES objectives.Open source software, such as OpenSees, requires community support and participation. The objective of this Getting Started manual is to provide an introduction so that users of OpenSees can obtain, install, and begin using the software to solve problems.Download OpenSeesTo download and install OpenSees the user is required to download both the OpenSees and Tcl/Tk packages. The OpenSees and Tcl/Tk packages can both be downloaded from the OpenSees binaries webpage /binaries.html. This page can be found using the quick links pull down menu from any of the OpenSees web pages. The binaries download page will be similar to that shown below.At this page the user is required to download two files OpenSees.X.X.X.exe and tcl/tk Y.Y.Y. This can be done by selecting (clicking) on the links located in the box labeled DOWNLOAD Windows Binaries.The file downloaded by clicking on the OpenSees.X.X.X.exe link is a zip file, from which the OpenSees.X.X.X.exe file can be extracted using your favorite extractor. The user can place this executable anywhere they wish. It is recommended to place it in a directory near where all your scripts will be stored.The file downloaded by clicking the tcl/tk Y.Y.Y link is an installer for Tcl/Tk. By clicking on the file the user is brought through a series of screens. The first screen shows the package information for Y.Y.Y, the second screen has the license agreement, you must accept the license to proceed with the installation. The third screen specifies the installation mode and location. Here the user must change the default installation location from C:/Tcl to C:/Program Files/Tcl (there is a space between Program and Files), as shown in the image below.This is the only change the user must make. User now just keeps selecting Next until done.Run OpenSeesThere are three ways that OpenSees/Tcl commands can be executed: InteractiveCommands can be input directly at the propt, as shown in the figure (Win32 version): Execute Input File at OpenSees promptThis method is the most-commonly used one. An external file containing the input commands can be generateda-priori(inputFile.tcl) and be executed at the OpenSees prompt by using the source command. The generation of the input script files is presented in this chapter. The file execution is shown in the figure (Win32 version): Batch ModeThe previously-created input file containing the Tcl script commands necessary to execute the analsis can also be executed at the MS-DOS/Unix prompt, as shown in the figure (Win32 version):Problem DefinitionA portal frame will be used to demonstrate the OpenSees commands. A structural model will be defined first. Subsequently, a number of static and dynamic analyses will be defined and implemented.The structural model consists of the planar portal frame shown in the figure below:The columns and beam will be modeled as elastic elements. At a more advanced level, these elements can be replaced by more refined element models.In the analysis phase, the frame will be subjected to three different load cases:1. DISPLACEMENT-CONTROLLED LATERAL PUSHOVER;2. DISPLACEMENT-CONTROLLED REVERSED CYCLIC LATERAL LOADING;3. DYNAMIC GROUND-MOTION-INPUT TRANSIENT ANALYSIS.In all cases, however, the frame will be subjected to constant static gravity loads:Model BuilderDefining the model builder expands the Tcl command library to include OpenSees-specific commands, such as node and element definition, etc. Currently, there is only one model builder available, basic model builder, this is the model builder that includes all the commands presented in this library.The model builder also defines the number of dimensions (ndm) and degrees of freedom per node (ndf):model BasicBuilder -ndm $ndm For a 2-D problem, you really only need three degrees of freedom at each node, the two translations in the plane and the rotation about the planes normal:model basic -ndm 2 -ndf 3NodesAt this point the user needs to decide which units will be used. In this demonstration, inches and kips will be used for length and force. Seconds will be used for time.The assignment of node and element numbers is defined in the figure below:In a 2D problem only the x and y coordinates need to be defined, using the node command:node $nodeTag (ndm $coords) node 1 0 0node 2 504 0node 3 0 432node 4 504 432The boundary conditions are defined using the fix command:fix $nodeTag (ndf $ConstrValues)with three degrees of freedom per node are constrained:fix 1 1 1 1fix 2 1 1 1fix 3 0 0 0fix 4 0 0 0where a fixed constraint is defined with a 1, a free constraint is defined with a 0.Nodal masses are typically defined at the same time as the nodal coordinates. The nodal mass is used to calculate the eigenvalues and to perform the dynamic analysis. Only the nodal mass in the horizontal direction will be defined in this demonstration. Nodal masses can either be defined within the node command, or the can be appended using the mass command:mass $nodeTag (ndf $MassValues)mass 3 5.18 0. 0.mass 4 5.18 0. 0.The mass value was calculated by dividing the nodal weight (1/2 of the total super-structure weight) by the gravitational constant g (32 ft/sec):ElementsThe elastic columns and beams are defined using the elastic beam column element. The characteristics of a 2-D elastic element depend on the material modulus and the section area and moment of inertia. Because the elements in this frame represent reinforced-concrete elements, the value of 4227 ksi for the elastic modulus of concrete will be used.The following values represent the area and moment of inertia of the columns and beams:COLUMNSBEAMAreaIzThe transformation command defines how the element coordinates correlate to the global model coordinates. In a 2D problem, element orientation does not need to be considered, and can be the same for all elements. The linear transformation will be used in this demonstration:geomTransf Linear $transfTag geomTransf Linear 1The following commands define the two columns (element 1 and 2) and the beam (element 3):element elasticBeamColumn $eleTag $iNode $jNode $A $E $Iz $transfTagelement elasticBeamColumn 1 1 3 3600 4227 1080000 1element elasticBeamColumn 2 2 4 3600 4227 1080000 1element elasticBeamColumn 3 3 4 5760 4227 4423680 1RecordersThe recorder command is used to define the analysis output.The node recorder will be used to output the horizontal and vertical displacements at node 3 into a file named Node3.out:recorder Node -dof ($dof1 $dof2 .) $respTyperecorder Node -file Node3.out -time -node 3 -dof 1 2 dispThe element recorder will be used to output the element forces. Element forces for element 1 will be output into file Element1.out:recorder Element ($arg1 $arg2 .)recorder Element -file Element1.out -time -ele 1 forceSummary of Model-Building Input FileThe following is a compilation of all the commands necessary to build the model:model basic -ndm 2 -ndf 3# nodal coordinates:node 1 0 0node 2 504 0node 3 0 432node 4 504 432# bondary conditions:fix 1 1 1 1fix 2 1 1 1fix 3 0 0 0fix 4 0 0 0# nodal masses:mass 3 5.18 0. 0.mass 4 5.18 0. 0.# transformation:geomTransf Linear 1# connectivity:element elasticBeamColumn 1 1 3 3600 4227 1080000 1element elasticBeamColumn 2 2 4 3600 4227 1080000 1element elasticBeamColumn 3 3 4 5760 4227 4423680 1# recordersrecorder Node -file Node3.out -time -node 3 -dof 1 2 disprecorder Element -file Element1.out -time -ele 1 forceThe above commands can be input line by line at the OpenSees command prompt:Otherwise, they can be saved into an input file calledexample.tcl. This file can then be sourced in from the OpenSees command line:Loads and AnalysisIn OpenSees applying loads is a three-step process:1. You must first define the loads in a load pattern2. You must then define the analysis and its features3. The loads are then applied when you execute the analysis1. Load definitionLoads are defined using the pattern command. Three types of patterns are currently available:a. plain Pattern普通模式- this pattern is used to define the following:i. nodal loads, such as gravity loads and lateral loads (or load-controlled nodal displacements)ii. single-point constraints, such as displacement control at a node (typically used for a constant displacement at a node)iii. element loads, such as distributed gravity loads along the element (this is a new option, which still needs documentation).b. UniformExcitation Pattern（一致激励）- this type of pattern imposes a user-defined acceleration record to all fixed nodes, in a specified direction.c. MultipleSupport Pattern综合- this type of pattern imposes a user-defined displacement record at specified nodes, in a specified direction, or a ground-motion record.2. Analysis definition and featuresThe analysis-definition part of OpenSees allows the user to define the different linear and nonlinear analysis tools available. For each analysis, the following items need to be defined, preferably in this order:Constraints（边界条件）The constraints command is used to construct the ConstraintHandler object. Constraints enforce a relationship between degrees-of-freedom. The ConstraintHandler object determines how the constraint equations are enforced in the analysis.Numberer（内部编号方法）The numberer command is used to construct the DOF_Numberer object. The DOF_Numberer object determines the mapping between equation numbers and degrees-of-freedom - how degrees-of-freedom are numbered.System（处理带宽方法）The system command is used to construct the LinearSOE and LinearSolver objects to store and solve the system of equations in the analysis.Test（收敛准则）The test command is used to construct a ConvergenceTest object. Certain SolutionAlgorithm objects require a ConvergenceTest object to determine if convergence has been achieved at the end of an iteration step.Algorithm（运算法则）The algorithm command is used to construct a SolutionAlgorithm object, which determines the sequence of steps taken to solve the non-linear equation.Integrator（加载方式）The integrator command is used to construct the Integrator object. The Integrator object determines the meaning of the terms in the system of equation object. The Integrator object is used for the following: determine the predictive step for time t+dt specify the tangent matrix and residual vector at any iteration determine the corrective step based on the displacement increment dUAnalysis（计算类型）The analysis command is used to construct the Analysis object. This analysis object is constructed with the component objects previously created by the analyst. All currently-available analysis objects employ incremental solution strategies. There are three types of analysis currently available:Static AnalysisTransient AnalysisVariableTransient Analysis3. Analysis executionThe analysis is executed using the analyze command. This command moves the analysis forward by the specified number of steps.Gravity LoadsGravity loads are independent of the type of lateral loading and here they are considered part of the structural model.NODAL FORCES & MOMENTSBecause the beam is an elastic element, the vertical load distributed along the horizontal member can be represented by nodal forces and moments. The nodal forces are distributed equally to the two end nodes. The nodal bending moments are equal and opposite:The nodal force is equal to one half of the superstructure weight:the distributed load is calculated by dividing the total load by the beam length:The bending moment is then calculated from the distributed load:LOAD PATTERN DEFINITIONLike all loads in OpenSees, gravity loads require two steps. The first step defines the load into a load pattern, the second applies the load pattern and the associated gravity load. The plain pattern command with a linear time series is used in the load definition:pattern Plain $patternTag (TimeSeriesType arguments) load $nodeTag (ndf $LoadValues)pattern Plain 1 Linear load 3 0.0 -2000 -168074load 4 0.0 -2000 168074CREATE ANALYSISThe constraints command is used to construct the ConstraintHandler object. Constraints enforce a relationship between degrees-of-freedom. The ConstraintHandler object determines how the constraint equations are enforced in