ABSTRACT
Existing methods of moving load identification can be broadly classified into two categories, with one based on a continuous bridge model and modal superposition technique to decouple the equation of motion and the subsequent solution using optimization schemes as in Chapters 5 and 6. The second category is based on discrete bridge model with the finite element method to decouple the equation of motion, such as the state space approach in Chapter 7 and the finite element method (FEM) in Chapter 9. The modal superposition technique has good accuracy for identification but it demands extensive computation whenmultiple vehicles cross a multi-span bridge structure. The FEM approach is flexible when dealing with vehicular axle-loads moving on top of a bridge system with complex boundary conditions. However, a great deal of care must be used in transforming the displacement or strain to velocities and accelerations (O’Connor and Chan, 1988). Numerical differentiationmay lead to large error in the identified results. This chapter introduces the moving load identification through the generalized
orthogonal function expansion to overcome the above computation problem. The method has efficient computational performance and good identification accuracy, especially with the orthogonal function smoothing technique to obtain the velocities and accelerations from the measured strains (Zhu and Law, 2001a). Orthogonal functions, such as the generalized orthogonal functions and wavelets, are introduced in Section 8.2. The moving load identification with these functions is presented in Section 8.3. The applications by numerical simulations and laboratory experiments are discussed in Sections 8.4 and 8.5.
