OpenSees » SRC » reliability » analysis » curvature

FirstPrincipalCurvature.cpp

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00001 /* ****************************************************************** **
00002 **    OpenSees - Open System for Earthquake Engineering Simulation    **
00003 **          Pacific Earthquake Engineering Research Center            **
00004 **                                                                    **
00005 **                                                                    **
00006 ** (C) Copyright 2001, The Regents of the University of California    **
00007 ** All Rights Reserved.                                               **
00008 **                                                                    **
00009 ** Commercial use of this program without express permission of the   **
00010 ** University of California, Berkeley, is strictly prohibited.  See   **
00011 ** file 'COPYRIGHT'  in main directory for information on usage and   **
00012 ** redistribution,  and for a DISCLAIMER OF ALL WARRANTIES.           **
00013 **                                                                    **
00014 ** Developed by:                                                      **
00015 **   Frank McKenna (fmckenna@ce.berkeley.edu)                         **
00016 **   Gregory L. Fenves (fenves@ce.berkeley.edu)                       **
00017 **   Filip C. Filippou (filippou@ce.berkeley.edu)                     **
00018 **                                                                    **
00019 ** Reliability module developed by:                                   **
00020 **   Terje Haukaas (haukaas@ce.berkeley.edu)                          **
00021 **   Armen Der Kiureghian (adk@ce.berkeley.edu)                       **
00022 **                                                                    **
00023 ** ****************************************************************** */
00024                                                                         
00025 // $Revision: 1.5 $
00026 // $Date: 2003/03/04 00:38:57 $
00027 // $Source: /usr/local/cvs/OpenSees/SRC/reliability/analysis/curvature/FirstPrincipalCurvature.cpp,v $
00028 
00029 //
00030 // Written by Terje Haukaas (haukaas@ce.berkeley.edu) 
00031 //
00032 
00033 #include <FirstPrincipalCurvature.h>
00034 #include <FindCurvatures.h>
00035 #include <LimitStateFunction.h>
00036 #include <Vector.h>
00037 
00038 
00039 FirstPrincipalCurvature::FirstPrincipalCurvature()
00040 :FindCurvatures(), curvatures(1)
00041 {
00042 }
00043 
00044 FirstPrincipalCurvature::~FirstPrincipalCurvature()
00045 {
00046 }
00047 
00048 
00049 int
00050 FirstPrincipalCurvature::computeCurvatures(ReliabilityDomain *theReliabilityDomain)
00051 {
00052 
00053         // "Download" limit-state function from reliability domain
00054         int lsf = theReliabilityDomain->getTagOfActiveLimitStateFunction();
00055         LimitStateFunction *theLimitStateFunction = 
00056                 theReliabilityDomain->getLimitStateFunctionPtr(lsf);
00057 
00058         // Get hold of 'u' and 'alpha' at the two last steps
00059         Vector last_u = theLimitStateFunction->designPoint_u_inStdNormalSpace;
00060         Vector secondLast_u = theLimitStateFunction->secondLast_u;
00061         Vector lastAlpha = theLimitStateFunction->normalizedNegativeGradientVectorAlpha;
00062         Vector secondLastAlpha = theLimitStateFunction->secondLastAlpha;
00063 
00064         // Compute curvature according to Der Kiureghian & De Stefano (1992), Eq.26:
00065 
00066         // Initial computations
00067         Vector uLastMinus_u = last_u - secondLast_u;
00068         double signumProduct = secondLastAlpha ^ uLastMinus_u;
00069         double alphaProduct = secondLastAlpha ^ lastAlpha;
00070         double sumSquared = 0.0;
00071 
00072         // Compute norm of the difference vector
00073         for ( int i=0; i<last_u.Size(); i++ ) {
00074                 sumSquared += uLastMinus_u(i)*uLastMinus_u(i);
00075         }
00076 
00077         double norm_uLastMinus_u = sqrt(sumSquared);
00078 
00079         // Check sign and compute curvature
00080         if (fabs(signumProduct)==(signumProduct)) {
00081                 curvatures(0) = acos(alphaProduct) / norm_uLastMinus_u;
00082         }
00083         else {
00084                 curvatures(0) = -acos(alphaProduct) / norm_uLastMinus_u;
00085         }
00086 
00087         return 0;
00088 }
00089 
00090 
00091 Vector
00092 FirstPrincipalCurvature::getCurvatures()
00093 {
00094         return curvatures;
00095 }
00096 
00097

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