Engineering Properties of Long-Period Earthquake Motion

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The acceleration response spectra of 1983 Nihon-kai Chubu earth-quake and those of 1985 Mexico earthquake were found larger than the design spectra of high-rise buildings and of long span bridges. The object of this research is to suggest the suitable design spectra for the long span bridges considering the following problems. 1) Estimation of the long period ground motion and the response spectra of Nihon-kai Chubu earthquake and other large earthquakes from the JMA strong motion records, SMAC accelerogram and the sloshing records of the huge tanks. 2) Error estimation of the seismic records of SMAC or SAMTAC accelerogram in long period from the vibration testings. 3) Estimation of the long period ground motion at Akashi using semi-empirical method and of the response spectra of that huge earthquake.The results of this research are summarized as follows: 1) The seismograph was set near the abutment of Akashi Kaikyo Ohashi (Honshu Shikoku Bridge) to observe the long-period ground motions. 3 earthquakes were recorded until now and the long-period velocity record of 11/2/1989 Iwate-ken Oki earthquake was successfully observed. 2) One of our investigators proposed the semi-empirical method to estimate the large earthquake ground motion. This method was applied to estimate the huge ground motion near Akashi, and the response spectra were calculated to compare with the design spectra of Akashi Kaikyo Ohashi. The ground motion of Nihon-kai Chubu earthquake was also simulated using this method. 3) The sloshing of the large tanks at Niigata was studied to estimate the long-period response spectra of Nihon-kai Chubu earthquake. 4) The correction of the digital accelerograms in long-period domain and the saturated JMA records were investigated to calculate more accurate response spectra.