Response Analysis of Civil Engineering Structures Subjected to Earthquake Motions
Ground Vibration Section, Public Works Research Institute, Ministry of Construction, 2-308, Mitsuwadai Heights, 5-29 Mitsuwadai, Chiba City, Chiba Prefecture, Japan
The Niigata Earthquake, measuring a magnitude of 7.5 on the Richter scale, hit the northwestern part of Honshu, Japan, on June 16th, 1964. The epicenter was under the sea about 55 km north from Niigata city, and the hypocentral depth was 20 to 30 km. The earthquake brought about severe damage to various engineering structures in the alluvial plain near the mouth of the Shinano River and the Agano River. Especially in the vicinity of the mouth of the Shinano River where loose sand layers plus a high water table exist, many modernstructures such as reinforced concrete buildings, highway bridges, harbor structures, etc. sustained heavy damage due to unexpectedly large deformations and settlements. This particular earthquake emphasized the importance of the dynamic effects of earthquake motions, as well as the effects of liquefaction phenomena of the ground soils. Two sets of strong motion accelerographs, installed in the basement floor and the roof of a heavily inclined 4-story apartment building located along the Shinano River, triggered the complete acceleration records of the earthquake. The peak accelerations at the basement are about 150 gals in the lateral direction, and 50 gals in the vertical direction. It was noted that these accelerations were not so large, when considering the severeness of the damage.