Two basically different approaches are available for evaluating structural response to dynamic loads: deterministic and nondeterministic. The choice of method to be used in any given case depends upon how the loading is defined. If the time variation of loading is fully known, even though it may be highly oscillatory or irregular in character, it will be referred to herein as a prescribed dynamic loading; and the analysis of the response of any specified structural system to a prescribed dynamic loading is defined as a deterministic analysis. On the other hand, if the time variationisnotcompletelyknownbutcanbedefinedinastatisticalsense,theloading is termed a random dynamic loading; and its corresponding analysis of response is defined as a nondeterministic analysis. The principal emphasis in this text is placed on development of methods of deterministic dynamic analysis; however, Part Four is devoted to presenting an introduction to nondeterministic methods of analysis and PartFivecontainsachapterdealingwiththeapplicationofnondeterministicmethods of analysis in the field of earthquake engineering.