This chapter will serve as the introduction of succeeding chapters, especially chapters in Part II-Bridge Behavior and Modeling. Brief discussion of various bridge structural forms will be made first in this chapter, whereas more details on each bridge type will be covered in their individual chapters (Chapters 4 through 12). Approximate and refined analysis methods with their advantages and disadvantages will then be briefly mentioned (Coletti and Pucket 2012). Although all methods can be categorized as finite element method (FEM), levels of approximation and accuracy are different among various modeling methods. With today’s advancing of computer analysis tools, there is a certain advantage to a adopting two-dimensional (2D) model in grillage or three-dimensional (3D) model, as called refined analysis models, over one-dimensional (1D) model, as termed approximate analysis model. Subsequently, the principle of FEM of all types will be presented in Chapter 3.