C EPSEQU    SOURCE    CHAT      05/01/12    23:41:24     5004           
C EPSEQU     SOURCE    INSL       24/10/96    
      SUBROUTINE EPSEQU(EPEQ,SEQ,IPLA,ICAL,IPOS,EX,RB,EPO1,EPO,EMAX)
C
      IMPLICIT INTEGER(I-N)
      IMPLICIT REAL*8(A-H,O-Z)
C
C                  *******************************
C                  *** COURBE DE COMPRESSION   ***
C                  ***     UNIAXIALE           ***
C                  *******************************
C-------------------------------------------------------------------
      TU=RB
      EPO2=EPO
      IF(IPOS.EQ.1) EPO2=EPO1
      IF(SEQ.GE.TU) THEN
         SEQ =TU
         EPEQ=EPO2
         IPLA=2
         GOTO 100
      ENDIF
C-------------------------------------------------------------------
C               PRE-PIC  ET POST-PIC LINEAIRES
C-------------------------------------------------------------------
      IF(IPLA.NE.0) THEN
        EPEQ=EMAX-SEQ*(EMAX-EPO2)/TU
        GOTO 100
      ENDIF
      IF(ICAL.NE.0) THEN
        EPEQ=SEQ/EX
        GOTO 100
      ENDIF
C-------------------------------------------------------------------
C                INSA_LBS1  ( PRE-PIC HYPERBOLE)
C-------------------------------------------------------------------
        EPEQ=0.D0
        IF(SEQ.EQ.0.D0.OR.EPO2.EQ.0.D0.OR.TU.EQ.0.D0) GOTO 100
C
        CC3=EPO2*EPO2
        BB3=CC3*(EX/SEQ-EX/TU+2.D0/EPO2)
        DELT=BB3*BB3-4.D0*CC3
C
        IF(DELT.EQ.0.D0) THEN
          EPEQ=EPO2
          GOTO 100
        ENDIF
        IF(DELT.GT.0.D0) EPEQ=(BB3-DSQRT(DELT))/2.D0
C-------------------------------------------------------------------
  100 CONTINUE
      RETURN
      END