Development and Usage Of Composite and Hybrid Building Structure in Japan

Composite and Hybrid Structures (CHS) provide many advantages over those employing conventional systems. Since the available design codes in Japan do not cover these systems, the current Japanese Building standard Law requires detailed experimental and/or analytical studies before the building permit for a structure with CHS can be issued. As part of the U.S.-Japan Cooperative Earthquake Research Program on Composite and Hybrid structures, three major types of composite and hybrid systems are being studied. These include concrete-filled tubular columns (CFT), reinforced concrete columns with steel beams (RCS), and reinforced concrete cores with steel perimeter frames (HWS). Among other objectives, these studies are expected to lead to design guidelines which can be incorporated in the Building Standard Law. The availability of these guidelines are expected to encourage the Japanese designers to use CHS more frequently. This paper provides an overview of the ongoing studies in Japan. After a brief historical review of each system, the important issues related to each system are summarized. Planned and ongoing studies for each group of composite systems are also described.