OpenSEES学习笔记(2)

（2）定义分析中的数据图

八、重力荷载

（1）定义重力荷载

（2）运行重力分析

九、静力分析

（1）定义静力推覆分析。

这条命令将在重力荷载被定义和应用之后运行。

（2）运行静力推覆分析。

当运行静力推覆分析时可能用一条命令即可，而单分析参数环境下通常不容易收敛。因些写个脚本试用多个算法增加收敛的可能性。

或

十、动力分析

（1）定义动力地面动动分析

（2）运行动力地面运动分析

十一、关于OpenSEES例子的介绍。

通常在建立分析模型时，重力分析是其中的一部分。 （一）建立模型 1、弹性单元

2、非弹性单元：包括两种截面类型，a、单轴截面；b、纤维截面。 3、水平荷载：a、静力推覆（包括单调加载和循环往复加载）；b、随时间变化的动力加载（动力分析）：包括均匀正弦波、多点激励正弦波、均匀地震波、多点激励地震波、双向激励地震波

（二）分析过程 1、建立模型

（1）定义模型维数和自由度数 （2）定义节点坐标

（3）定义节点约束——边界条件 （4）定义节点质量

（5）定义单元和单元连接 （6）定义输出记录

以上为OpenSEES建立模型时的常规步骤。 2、定义和施加竖向荷载

（1）定义节点或单元的竖向荷载

（2）定义静力分析参数——容差、算法、约束，方程和加载步 （3）运行分析

（4）保持竖向荷载为常数（为后续的水平荷载分析） （5）重置时间为0。 3、定义和施加水平荷载

（1）定义荷载模式（节点荷载为静力分析，支点运动为地震分析） （2）水平荷载分析参数（容差或时间/位移增量） A、静力水平荷载分析：定义位移增量和位移加载路径

B、动力水平荷载分析：定义输入地震动及所有相关参数，例如地震波调整和输入类型； 定义分析持时和时间增量；定义阻尼。 (3)运行分析

十二、OpenSees初级入门篇及简单例子

To conduct a simulation in OpenSees, the user creates an input file (a script). A script is just a series of commands that instruct the interpreter what to do. In the case of OpenSees, the commands either create objects or invoke methods (procedures) on those objects. In OpenSees there are 3 types of objects the user must create: 1. Modeling: The user first creates a ModelBuilder object which defines the type of model, and commands available for building the model. With a ModelBuilder defined the user then creates the Element, Node, LoadPattern and Constraint objects that define the model. In this primer the use of the basic ModelBuilder will be demonstrated.

2. Analysis: After the user has defined the model, the next step is to create the Analysis object for analyzing the model. This may be a simple static linear analysis or a transient non-linear analysis. In OpenSees, an Analysis object is composed of several component objects and these define the type of analysis that is performed. The component objects consist of the following: SolutionAlgorithm, Integrator, ConstraintHandler, DOF Numberer, SystemOfEqn, Solver, and ConvergenceTest. This approach provides a great deal of flexibility in how an analysis is conducted, but requires knowledge on behalf of the user as to what the different options provide.

3. Output Specification: Once the model and analysis have been defined, the user must specify what is to be monitored during the analysis. OpenSees by default will producde no output. The outputs specified could for example be the displacement history at a node or internal stress state at some material point in an element element. The user typically creates Recorder objects to store what the user wants to examine, though the user can also use the tcl puts command. In each of the following examples, tcl scripts are used to create model, analysis and a recorder objects. After these objects have been created, the analysis is performed. The analyses performed on these models consist of simple static gravity analysis and pushover analysis and transient analysis of models subjected to earthquake excitation.

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