ON TEST PROCEDURE OF DETERMINING THE DYNAMICAL CHARACTERISTICS OF STRUCTURE

Abstract

For establishment of antiseismic design, it is one of the most important problems toevaluate dynamical characteristics of structure. The method of determining the dynam-ical characteristics of actual structures by the seismic test is considered as one of effec-tive approach to this problem, but practical procedure of the test and evaluation of theresults must be precisely examined in the application of this method concerning withobject of the test and also with type of the structure.In this paper discussed are the various questions on the test for dynamical character-istics of actual structures in the case of the forced vibration test and the measurement ofmicro-tremors of structure. And then, regarding to the natural periods and critical damp-ing ratios that are considered as basic quantities of the structure in elastic range, themethod of determining these quantities are applied on the five story steel framed structurewith rectangular plan.From the results of the steady-state forced vibration test and of the measurement ofmicro-tremors of the structure, resonance curves, auto-correlation function, and spectraldensity are calculated. With respect to these numerical results, estimation of natural pe-rinds and critical damping ratios is discussed.Some conclusions are pointed out as follows:1) It should be careful for us to evaluate the reasonable value of critical dampingratio from the resonance curve because of the various test conditions.2) The exsct values of lower natural periods can be easily computed from spectraldensity, but some correction for the computation procedure of spectral density shouldbe required to evaluate critical damping ratio from spectral density as to input and out-put.