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**    OpenSees - Open System for Earthquake Engineering Simulation    **

**          Pacific Earthquake Engineering Research Center            **

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**   Frank McKenna (fmckenna@ce.berkeley.edu)                         **

**   Gregory L. Fenves (fenves@ce.berkeley.edu)                       **

**   Filip C. Filippou (filippou@ce.berkeley.edu)                     **

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// $Revision: 1.2 $

// $Date: 2007-06-28 21:46:43 $

// $Source: /usr/local/cvs/OpenSees/SRC/material/uniaxial/Concrete07.h,v $

// Written: Jon Waugh, Iowa State University

// Created: 11/2005

//

// Description: This file contains the class defination for Uniaxial material Concrete07 

//                              A simplified form of Chang & Mander Concrrete model from 1994.

#ifndef Concrete07_h

#define Concrete07_h

#include <UniaxialMaterial.h>

class Concrete07 : public UniaxialMaterial

{

        public:

                Concrete07 (int tag, double FPC, double EPSC0, double EC, double FPT, double ESPT0, double XCRP, double XCRN, double R);

                Concrete07 ();

                ~Concrete07();

                int setTrialStrain(double strain, double strainRate = 0.0);

                int setTrial (double strain, double &stress, double &tangent, double strainRate = 0.0);

                double getStrain(void);      

                double getStress(void);

                double getTangent(void);

                double getInitialTangent(void) {return Ec;}

                int commitState(void);

                int revertToLastCommit(void);    

                int revertToStart(void);        

                UniaxialMaterial *getCopy(void);

                int sendSelf(int commitTag, Channel &theChannel);  

                int recvSelf(int commitTag, Channel &theChannel,

                 FEM_ObjectBroker &theBroker);    

                void Print(OPS_Stream &s, int flag =0);

        protected:

        private:

      /*** Material Properties ***/

      double fpc;                               // Compressive strength

      double epsc0;                             // Strain at compressive strength

          double Ec;                            // Initial Young's modulus;

          double fpt;                           // Tensile strength

          double epst0;                         // Strain at tensile strength

          /*** Model Variables ***/

      double xcrn;                              // nondimensional critical strain used to determine spalling

          double xsp;                           // nondimensional spalling strain

          double xcrp;                          // nondimensional critical strain used to determine cracking

          double xcrk;                          // nondimensional cracking strain

          double nn;                            // parameter to control stress-strain curve in compression

          double np;                            // parameter to control stress-strain curve in tension

          double r;                                     // factor from Tsai's equation

          double e0;                            // origin of the shifted tension side.

      /*** CONVERGED History Variables ***/

      double CminStrain;                // Smallest previous concrete strain (compression)

          double CminStress;            // Stress that goes with CminStrain

          double CUnloadStrain;         // Previous partial unloading strain

          double CUnloadStress;         // Previous partial unloading stress

          double CUnloadStiffness;      // Previous partial unloading stiffness

          double CmaxStrain;            // Largest previous concrete strain (tension)

          double CmaxStress;            // Stress that goes with CmaxStrain (tension)

          double CReloadStrain;         // Previous partial reloading strain

          double CReloadStress;         // Previous partial reloading stress

          double CReloadStiffness;      // Previous partial reloading stiffness

          double C13Zero;                       // Strain where we reversed onto rule 13.

          double C13Strain;                     // Strain where we left reversed on rule 13

          double C13Stress;                     // Stress where we left reversed on rule 13

          int Cloading;                         // Flag for stressing/unstressing

                                                                // 1 = compressing the concrete

                                                                // -1 = uncompressing the concrete

                                                                // 0 = initial state

          bool Ccracked;                        // Flag for if the concrete has cracked

                                                                // true the concrete has cracked and assumed to have no tension capacity

                                                                // false the concrete has not cracked yet

          int Crule;                            // The rule we are following for this step

      /*** CONVERGED State Variables ***/

      double Cstrain;

      double Cstress;  

      double Ctangent;                  // Don't need Ctangent other than for revert and sendSelf/recvSelf

                                                                // Storing it is better than recomputing it!!!

      /*** TRIAL History Variables ***/

      double TminStrain;

          double TminStress;

          double TUnloadStrain;

          double TUnloadStress;

          double TUnloadStiffness;

          double TmaxStrain;

          double TmaxStress;

          double TReloadStrain;

          double TReloadStress;

          double TReloadStiffness;

          double T13Zero;

          double T13Strain;

          double T13Stress;

          int Tloading;

          bool Tcracked;

          int Trule;

      /*** TRIAL State Variables ***/

      double Tstrain;

      double Tstress;

      double Ttangent; // Not really a state variable, but declared here

                       // for convenience

          /*** Private functions to make life easier ***/

          // Calculates trial state variables based on the trail strain

      void determineTrialState (double dStrain);

          // Determines is a strain reversal has occured based on the trial strain

          void detectStrainReversal (double dStrain);

          // Calculates the value of y(x) and z(x)

          void calculateYandZ(double x, double& y, double& z, double n);

          // Calculate the stress of the transition curve;

          void calculateStressTransition(double &fc, double &Et, double ec, double eI, double fI, double EI, double eF, double fF, double EF, int rule);

          // Calculate the envelope stress for a given nondimensional strain.

          void envelope(double x, double& fc, double& Et, int flag);

          // Calculate the stress-strain curve for Rule 13

          void calculate13Stress(double &fc, double &Et, double ec, double eI, double eF, double fF, double EF);

};

#endif