IMPROVED NONLINEAR ANALYTICAL METHOD FOR DAMAGE IDENTIFICATION OF FRAME STRUCTURES

The generalized inverse technique was used to solve the first order equation,and the trust-region reflective Newton method was used to solve the second order sensitivity equation.Considering the fast solving speed by the first order sensitivity equation and the high solving precision by the second order equation,a mixed iteration algorithm which was applied in structure damage detection was put forward.This algorithm uses the second order nonlinear analytical solution as the first substituting value,and then the first substituting value is modified based on the taylor series bias error using the solution of the first order sensitivity equation.The modal analysis program and damage identification program about space frame based on the finite element theory were carried out.Damage identification was studied using the mixed iteration algorithm which was mentioned in this paper.It shows that the mixed iteration algorithm has a better convergence and a faster iteration speed because the higher precision second order nonlinear analytical solution is adopted.