The modeling and analysis of structures using frequency-domain methods simplify the procedure of the modeling and analysis and provides better understanding of the response of the structures. There are different applications in frequency-domain structural modeling and analysis such as modeling and analysis in impact engineering, wave propagation in structures, and micro-resonators. The identification of the impact force and the impact location in structures are important for monitoring the condition of the structures and also for the design of the future structures. The complexity and nonlinearity of the impact incident makes it impractical to measure the impact force directly. In this study, a new method that uses the spectral finite element method (SFEM) is introduced in order to identify and locate the applied impact force. Using SFEM facilitates for the successfully identification of the high frequency content in the impact forces. Also, using SFEM allows for the identification of the impact force independent of the location of the impact force. The impact force identification and localization method is verified by experimental results. For designing and analyzing micro-resonators, it is required to do the frequency-analysis of these structures which provide the frequency characteristics and the frequency-response of the structures. In this study, a novel class of parametrically excited micro-resonators is introduced. The micro-resonator takes advantage of piezo-electric excitation which improves the performance of the micro-resonator over that of the micro-resonators with electrostatic excitation for certain applications.