What are the underlying principles and methodologies behind the application of finite element analysis $($FEA$)$ in civil engineering? Discuss the theoretical foundations of FEA, including the discretization of continuous structures into finite elements, the formulation of element stiffness matrices, and the assembly of global stiffness matrices. Furthermore, delve into the fundamental concepts of boundary conditions and load application within FEA models, elucidating their significance in accurately simulating structural behavior. Moreover, explore the theoretical underpinnings of numerical solution techniques such as matrix inversion and iterative methods employed to solve the system of equations generated by FEA. Additionally, analyze the theoretical considerations governing the selection of appropriate element types, material models, and mesh refinement strategies to ensure the accuracy and convergence of FEA simulations.