Abstract
A major earthquake occurred in central Taiwan on September 21, 1999. This earthquake was officially named the Chi-Chi earthquake. Many civil engineering structures such as dams, bridges and buildings were seriously damaged by surface faults in the focal region. Oil storage tanks of China Petroleum Corporation (CPC), the largest oil company in Taiwan, also suffered severe damage, although these sites were situated far from the epicenter and the accelerations observed during the earthquake were about 100 gal. The High Pressure Institute of Japan organized a damage survey team in early November to investigate the damage to CPC tanks.
Damage such as buckling of floating roofs, rupturing of shell plates, buckling of shell-to-roof joints, and deformation of equipment in CPC tanks was caused by liquid sloshing. Velocity response spectra estimated from the observed wave heights based on the Fire Service Law of Japan mostly agree with those calculated from the strong motion records near the tank sites. On the other hand, a detail dynamic response analysis of a liquid in a tank subjected to two-dimensional excitations showed that the calculation results do not agree well with the liquid wave heights observed for one tank site but agree for two sites. This means that evaluation of the input ground motion just at the tank site is very important even if the wavelengths is long at long-period range.
