Shin Koyama

Recorded Responses of Building Structures during the 2011 Tohoku-Oki Earthquake with Some Implications for Design Practice

During the 2011 Tohoku-oki earthquake, a large number of response records from various types of buildings were obtained. The records give us the actual motions of buildings during the exceptionally large earthquakes that are considered comparable with design earthquakes. Various types of earthquake response records have been collected, and their properties with several buildings that will exhibit implications for structural design are discussed.

Dynamic Characteristics of a 55-Story Building Before and After Retrofit

A sparsely instrumented 55-story building in Osaka, Japan, recorded unprecedented severe and long-duration, long-period resonant responses during the March 11, 2011, M9.0 Tohoku earthquake that occurred at 767 km distance. Thereafter, studies of the records resulted in implementation of a significant retrofit design, comprising dampers and buckling restrained braces (BRBs). The responses of the retrofit building were subsequently recorded during the April 24, 2016, M7.3 Kumamoto earthquake that occurred 478 km away, but at an azimuth nearly opposite to that for the Tohoku event. The earthquake records and ambient response data analyzed in this study represent a rare opportunity to assess the impact of retrofitting on an instrumented tall building subjected to strong long-period shaking from distant earthquakes. As expected, the fundamental frequency and critical damping ratio of the building increased, albeit by small amounts, after the retrofit. Increased damping percentage is a positive finding, and suggests that even larger percentages might be attained for shaking stronger than occurred following the 2016 event. The records indicate that the building still experiences significant resonance and torsion, as well as a beating effect.

Earthquake Motion Observation In And Around 8-Story Src Building

Building Research Institute (BRI), Ministry of Construction, Japan, started the strong motion observation project in 1957. The observation network has been enriched and enlarged in the past forty years. BRI is now operating several networks with a number of strong motion instruments. In this paper, we are introducing a new system that is installed to buildings and underground at BRI, and some observation results.