OpenSees开发（二）源码分析——平面桁架静力有限元分析实例

这是一个平面桁架静力分析算例，代码位于  OpenSees2.3.0\EXAMPLES\Example1\main.cpp

这里先给出原始源代码：

// standard C++ includes

#include <stdlib.h>

#include <OPS_Globals.h>
#include <StandardStream.h>

#include <ArrayOfTaggedObjects.h>

// includes for the domain classes
#include <Domain.h>
#include <Node.h>
#include <Truss.h>
#include <ElasticMaterial.h>
#include <SP_Constraint.h>
#include <LoadPattern.h>
#include <LinearSeries.h>
#include <NodalLoad.h>

// includes for the analysis classes
#include <StaticAnalysis.h>
#include <AnalysisModel.h>
#include <Linear.h>
#include <PenaltyConstraintHandler.h>
#include <DOF_Numberer.h>
#include <RCM.h>
#include <LoadControl.h>
#include <BandSPDLinSOE.h>
#include <BandSPDLinLapackSolver.h>


// init the global variabled defined in OPS_Globals.h
StandardStream sserr;
OPS_Stream *opserrPtr = &sserr;

double        ops_Dt = 0;
// Domain       *ops_TheActiveDomain = 0;
Element      *ops_TheActiveElement = 0;



// main routine
int main(int argc, char **argv)
{
    //
    //	now create a domain and a modelbuilder
    //  and build the model
    //

    Domain *theDomain = new Domain();
    
    // create the nodes using constructor: 
    //		Node(tag, ndof, crd1, crd2)
    // and then add them to the domain
    
    Node *node1 = new Node(1, 2,   0.0,  0.0);
    Node *node2 = new Node(2, 2, 144.0,  0.0);
    Node *node3 = new Node(3, 2, 168.0,  0.0);    
    Node *node4 = new Node(4, 2,  72.0, 96.0);        
    theDomain->addNode(node1);
    theDomain->addNode(node2);
    theDomain->addNode(node3);
    theDomain->addNode(node4);
    
    // create an elastic material using constriuctor:  
    //		ElasticMaterialModel(tag, E)

    UniaxialMaterial *theMaterial = new ElasticMaterial(1, 3000);
    
    // create the truss elements using constructor:
    //		Truss(tag, dim, nd1, nd2, Material &,A)
    // and then add them to the domain
    
    Truss *truss1 = new Truss(1, 2, 1, 4, *theMaterial, 10.0);
    Truss *truss2 = new Truss(2, 2, 2, 4, *theMaterial,  5.0);    
    Truss *truss3 = new Truss(3, 2, 3, 4, *theMaterial,  5.0);        
    theDomain->addElement(truss1);
    theDomain->addElement(truss2);
    theDomain->addElement(truss3);    
    
    // create the single-point constraint objects using constructor:
    //		SP_Constraint(tag, nodeTag, dofID, value)
    // and then add them to the domain
    
    SP_Constraint *sp1 = new SP_Constraint(1, 1, 0, 0.0);
    SP_Constraint *sp2 = new SP_Constraint(2, 1, 1, 0.0);    
    SP_Constraint *sp3 = new SP_Constraint(3, 2, 0, 0.0);
    SP_Constraint *sp4 = new SP_Constraint(4, 2, 1, 0.0);    
    SP_Constraint *sp5 = new SP_Constraint(5, 3, 0, 0.0);
    SP_Constraint *sp6 = new SP_Constraint(6, 3, 1, 0.0);        
    theDomain->addSP_Constraint(sp1);
    theDomain->addSP_Constraint(sp2);
    theDomain->addSP_Constraint(sp3);
    theDomain->addSP_Constraint(sp4);    
    theDomain->addSP_Constraint(sp5);    
    theDomain->addSP_Constraint(sp6);    

    // construct a linear time series object using constructor:
    //		LinearSeries()
    
    TimeSeries *theSeries = new LinearSeries();
    
    // construct a load pattren using constructor:
    //		LoadPattern(tag)
    // and then set it's TimeSeries and add it to the domain
    
    LoadPattern *theLoadPattern = new LoadPattern(1);
    theLoadPattern->setTimeSeries(theSeries);
    theDomain->addLoadPattern(theLoadPattern);
    
    // construct a nodal load using constructor:
    //		NodalLoad(tag, nodeID, Vector &)
    // first construct a Vector of size 2 and set the values NOTE C INDEXING
    // then construct the load and add it to the domain
    
    Vector theLoadValues(2);
    theLoadValues(0) = 100.0;
    theLoadValues(1) = -50.0;
    NodalLoad *theLoad = new NodalLoad(1, 4, theLoadValues);
    theDomain->addNodalLoad(theLoad, 1);

    // create an Analysis object to perform a static analysis of the model
    //  - constructs:
    //    AnalysisModel of type AnalysisModel,
    //	  EquiSolnAlgo of type Linear
    //	  StaticIntegrator of type LoadControl
    //	  ConstraintHandler of type Penalty
    //    DOF_Numberer which uses RCM
    //    LinearSOE of type Band SPD
    // and then the StaticAnalysis object
    
    AnalysisModel     *theModel = new AnalysisModel();
    EquiSolnAlgo      *theSolnAlgo = new Linear();
    StaticIntegrator  *theIntegrator = new LoadControl(1.0, 1, 1.0, 1.0);
    ConstraintHandler *theHandler = new PenaltyConstraintHandler(1.0e8,1.0e8);
    RCM               *theRCM = new RCM();
    DOF_Numberer      *theNumberer = new DOF_Numberer(*theRCM);    
    BandSPDLinSolver  *theSolver = new BandSPDLinLapackSolver();       
    LinearSOE         *theSOE = new BandSPDLinSOE(*theSolver);        

    StaticAnalysis    theAnalysis(*theDomain,
				  *theHandler,
				  *theNumberer,
				  *theModel,
				  *theSolnAlgo,
				  *theSOE,
				  *theIntegrator);

    // perform the analysis & print out the results for the domain
    int numSteps = 1;
    theAnalysis.analyze(numSteps);
    opserr << *theDomain;

    exit(0);
}	

接下去一步一步解释代码：

	// 创建一个有限元模型
	Domain *theDomain = new Domain();

	// 创建4个节点，详细见说明1
	Node *node1 = new Node(1, 2,   0.0,  0.0);
	Node *node2 = new Node(2, 2, 144.0,  0.0);
	Node *node3 = new Node(3, 2, 168.0,  0.0);    
	Node *node4 = new Node(4, 2,  72.0, 96.0);   

说明1：Node构造函数

位于OpenSees2.3.0\SRC\domain\node\Node.cpp

源码定义如下：

*****************************************************

Node::Node(int tag, int ndof, double Crd1, double Crd2)

:DomainComponent(tag,NOD_TAG_Node),

 numberDOF(ndof), theDOF_GroupPtr(0),

 Crd(0), 。。。。。。。

{

  Crd = new Vector(2);

  (*Crd)(0) = Crd1;

  (*Crd)(1) = Crd2;

。。。。。。

*****************************************************

参数tag为该节点的标签，指定给基类

:DomainComponent(tag,NOD_TAG_Node), NOD_TAG_Node是一个枚举值，表明该DomainComponent对象是一个节点类型；

 

ndof该节点的自由度，本例中，节点都为两个自由度；

Crd1, Crd2为该2维节点的坐标，赋于成员变量Crd，这是一个类数组的数据类型，创建了一个含该点坐标信息的数组。

	// 将4个节点对象加入有限元模型中
	// 如果两个node对象tag相同，则会返回失败
	theDomain->addNode(node1);
	theDomain->addNode(node2);
	theDomain->addNode(node3);
	theDomain->addNode(node4);

	// 创建一个弹性材料，见说明2
	UniaxialMaterial *theMaterial = new ElasticMaterial(1, 3000);

说明2：创建材料对象

*****************************************************

UniaxialMaterial *theMaterial = new ElasticMaterial(1,3000);

*****************************************************

 

UniaxialMaterial类官方说明：

http://opensees.berkeley.edu/OpenSees/api/doxygen2/html/classElasticMaterial.html

其中，ElasticMaterial为UniaxialMaterial派生类

 

意为理想弹性材料

http://opensees.berkeley.edu/wiki/index.php/Elastic_Uniaxial_Material

 

构造函数

申明：

*****************************************************

ElasticMaterial(int tag, double E, double eta =0.0);   

*****************************************************

实现：

*****************************************************

ElasticMaterial::ElasticMaterial(int tag, double e, doubleet)

:UniaxialMaterial(tag,MAT_TAG_ElasticMaterial),

 trialStrain(0.0),  trialStrainRate(0.0),

 E(e), eta(et), parameterID(0)

{

 

}

*****************************************************

其中，第一个参数tag为标签，传递给基类构造函数，e为弹性模型，et为材料阻尼比，默认为0.

	// 创建一个工况，编号为1，暂时未知
	LoadPattern *theLoadPattern = new LoadPattern(1);
	theDomain->addLoadPattern(theLoadPattern);

	// 暂时未知这句话什么意思
	theLoadPattern->setTimeSeries(new LinearSeries());

	// 创建一个节点荷载向量
	Vector theLoadValues(2);
	theLoadValues(0) = 100.0;
	theLoadValues(1) = -50.0;

	// 第一个参数tag标签，第二个参数表明施加点荷载的节点tag，第三个参数是一个向量，表明在第一维度施加100个单位力，第二维度施加反方向50单位力
	NodalLoad *theLoad = new NodalLoad(1, 4, theLoadValues);

	// 将NodalLoad对象加入模型，1表示加入的工况编号
	theDomain->addNodalLoad(theLoad, 1);

	// 如果new NodalLoad后的节点编号未在模型中找到，返回失败
	// 如果addNodalLoad第2个参数所表示的工况编号不存在，返回失败

这里为了避免内存泄漏，也为了使代码的封装性更强，我更改了一部分代码：

    AnalysisModel     *theModel = new AnalysisModel();
    EquiSolnAlgo      *theSolnAlgo = new Linear();
    StaticIntegrator  *theIntegrator = new LoadControl(1.0, 1, 1.0, 1.0);
    ConstraintHandler *theHandler = new PenaltyConstraintHandler(1.0e8,1.0e8);
    RCM               *theRCM = new RCM();
    DOF_Numberer      *theNumberer = new DOF_Numberer(*theRCM);    
    BandSPDLinSolver  *theSolver = new BandSPDLinLapackSolver();       
    LinearSOE         *theSOE = new BandSPDLinSOE(*theSolver);        

    StaticAnalysis    theAnalysis(*theDomain,
				  *theHandler,
				  *theNumberer,
				  *theModel,
				  *theSolnAlgo,
				  *theSOE,
				  *theIntegrator);

改为：

	// 分析对象封装
	struct MyStaticAnalysis : public StaticAnalysis
	{
		ConstraintHandler	*pConstraintHandler;
		DOF_Numberer		*pDOF_Numberer;
		AnalysisModel		*pAnalysisModel;
		EquiSolnAlgo		*pEquiSolnAlgo;
		LinearSOE		*pLinearSOE;
		StaticIntegrator	*pStaticIntegrator;

		MyStaticAnalysis(Domain *theDomain) : StaticAnalysis(*theDomain,
			*(pConstraintHandler = new PenaltyConstraintHandler(1.0e8,1.0e8)),
			*(pDOF_Numberer = new DOF_Numberer(*(new RCM()))),
			*(pAnalysisModel = new AnalysisModel()),
			*(pEquiSolnAlgo = new Linear()),
			*(pLinearSOE = new BandSPDLinSOE(*(new BandSPDLinLapackSolver()))),
			*(pStaticIntegrator = new LoadControl(1.0, 1, 1.0, 1.0))) {}

		~MyStaticAnalysis(){
			delete pConstraintHandler;
			delete pDOF_Numberer;
			delete pAnalysisModel;
			delete pEquiSolnAlgo;
			delete pLinearSOE;
			delete pStaticIntegrator;
		}
	};

	// 实例化分析模型对象
	MyStaticAnalysis &theAnalysis = *(new MyStaticAnalysis(theDomain));

	// perform the analysis & print out the results for the domain
	int numSteps = 1;
	theAnalysis.analyze(numSteps);

	// 释放分析对象
	delete &theAnalysis;
	
	// 模型信息打印
	opserr << *theDomain;

	// 查看4节点两个自由度上的位移
	Vector const &disp4node = theDomain->getNode(4)->getDisp();
	printf("x4: %lf, z4: %lf\n", disp4node[0], disp4node[1]);

	// 查看3个桁架单元的轴力
	Information trussInfo;
	for(int i=0; i<3; ++i)
	{
		Truss *pTruss = (Truss *)theDomain->getElement(i+1);
		pTruss->getResponse(2, trussInfo);
		printf("N%d: %lf\n", i+1, trussInfo.theDouble);
	}

	// Domain类的析构会释放加入domain的所有元素，所以node之类的对象不用单独析构
	delete theDomain;

编译——运行——屏幕输出：

第一自由度位移 0.530094，第二自由度位移-0.177894

杆件1轴力：43.94

杆件2轴力：-57.55

杆件3轴力：-55.31

与sap2000计算结果一致：

sap2000模型文件*.SDB(v14)和*.s2k文件，及修改后的源文件 first.cpp下载：

http://pan.baidu.com/s/1dDDKnb7