This book aims to provide practical guidance on the application of FEA to the seismic analysis of structures and equipment, and to inform the reader generally about seismic analysis. The intended audience is the practicing engineer (and to a lesser degree engineering managers). It is assumed that the reader has some understanding and experience of seismic engineering and FEA. Examples of actual applications of FEA to safety critical structures and plant are used to illustrate some of the techniques and guidelines given within this document. There is much literature on the subject of FEA, including other NAFEMS publications, and there is an abundance of literature on the subject of seismic engineering. In particular, the reader is referred to ASCE 4-98 [Ref 1], and its successor document ASCE/SEI 43-05 [Ref 2]. Although geared to seismic analysis of safety related nuclear structures, this publication offers good practical guidance that is generally applicable to seismic analysis.