Force Identification Of Space Truss Structures

Force identification is very important to not only the structural health monitor, but also to the daily maintenance and assessment of structures. In this thesis, the force identification of a space truss structure from the measured response by using both Tikhonov regularization and Genetic Algorithm (GA) is studied.Firstly, the forward problem of a space truss structure is discussed by using the finite element method. Both the displacements and strains of elements are obtained.Then, the equations between loads and element strains are deduced. The ill-posed equations are solved by using Tikhonov regularization. In this approach, the appropriate choice of a regularization parameter is the most important, which determines whether the solution can converge to the right ones. Presently, a method based on the Genetic Algorithm (GA) is proposed, which can achieve an optimal solution of the parameter in the whole range and therefore provide an efficient way for the parameter calculation. Here the generalized cross validation criterion, L-curve method and the Engl's criterion are used as the objective functions of GA.Finally, the methods above are used for identifying loads on a space truss structure. Numerical results show that good results can be achieved. The effects of the measurement number, their positions and error distribution on the identification results are further discussed.