Summary

Steel concentrically braced frames (CBFs) are an efficient structural system to achieve the large
lateral stiffness and strength required for buildings in high-seismic regions. While CBFs have remained
a popular system for decades, damage from past earthquakes and observations from laboratory tests
suggest that detailing of the bracing connections (connections between the brace member and frame
elements) remains a design challenge. Since the late 1990’s, more advanced CBF systems have been
implemented which replace the diagonal steel braces with vibration control devices, and which are
designed to remain damage free even after a major earthquake. One of the most commonly used
vibration control devices is the buckling-restrained brace (BRB). BRBs achieve equal strength in
tension and compression, and thereby assure stable seismic response of the structural system.
Research is continuing to further the reliability of steel braced frames. This presentation will introduce
the fundamentals of steel braced frames, discuss damage observed to steel buildings after the 2011
Tohoku earthquake of Japan, and discuss the author’s and his colleagues’ recent research. The
research includes a large-scale test program that subjected two-story steel braced frames to
bidirectional loading, and a series of shake-table tests that examined the effect of dynamic loading.
The presentation will highlight findings on the performance of bracing connections in CBFs, the effect
of out-of-plane loading on CBFs, and the out-of-plane stability of BRBs.

Biography

Dr. Taichiro Okazaki is an Associate Professor of Architectural and Structural Design at Hokkaido
University. He holds a B.E. and M.E. in Architecture and Architectural Engineering from Kyoto
University. He received his Ph.D. in Civil Engineering in 2004 from the University of Texas at Austin.
Prior to his appointment at Hokkaido University in January 2011, he was Researcher at the National
Research Center for Earth Science and Disaster Prevention of Japan, and Assistant Professor at the
University of Minnesota. Dr. Okazaki’s research interests are in the behavior of steel structures,
structural mechanics, and earthquake engineering. Dr. Okazaki has extensive experience with large-
scale tests of structural components and connections. He has been on the research team of three,
large-scale, shake-table test projects conducted at E-Defense. Dr. Okazaki is a member of a number
of professional societies including the Architectural Institute of Japan, the Japan Association for
Earthquake Engineering, and the American Society of Civil Engineers.