The C.I.T. Mark II electric analog type response spectrum analyzer for earthquake excitation studies

Abstract

The design of a response spectrum analyzer for earthquake excitation studies is described. Electric analog techniques are used, with a series inductance, capacitance, and resistance circuit forming a direct analog to the mechanical structure. The circuit arrangement permits a determination of system response for a sequence of periods at constant damping. Provision is made for obtaining zero damping in the circuit. An arbitrary function generator of the variable width film-photoelectric cell type is described. The results obtained with the function generator-spectrum analyzer system for a half-sine wave pulse are compared with the mathematically obtained exact answers for the zero damping case, and the accuracy of the system is shown to be satisfactory. This is a revision of a report originally issued as the "Sixth Technical Report", Office of Naval Research Contract N6 ONR-244, Task Order 25, Project Designation NR-081-095 by the California Institute of Technology dated July, 1954. The new model spectrum analyzer herein described has superseded the model discussed in this preceding report.