This book covers several related topics: the displacement method with matrix formulation, theory and analysis of structural dynamics as well as application to earthquake engineering, and seismic building codes. As computer technology rapidly advances and buildings become taller and more slender, dynamic behavior of such structures must be studied using state-of-the-art methodology with matrix formulation. Analytical accuracy and computational efficiency of dynamic structural problems depends on several key features: structural modeling, material property idealization, loading assumptions, and numerical techniques.