Toggle-brace-damper seismic energy dissipation systems

Energy dissipation systems are being increasingly employed in the United St ates to provide enhanced seismic protection for new and retrofit building a nd bridge construction. The hardware utilized includes yielding steel devic es, friction devices, viscoelastic solid devices, and mostly, so far, fluid viscous devices. This hardware has been used in either diagonal or chevron brace configurations. This paper presents three new configurations that ut ilize toggle-brace mechanisms to substantially magnify the effect of dampin g devices so that they can be utilized effectively in applications of small structural drift. Shake table testing of a large scale steel model structu re and analysis are used to demonstrate the utility of these configurations . The experimental results demonstrate substantial increases in the damping ratio despite the use of small size damping devices, and, accordingly, sig nificant attenuation of the seismic response of the tested stiff structure is observed. Moreover, the experimental results are found to be consistent with analytical predictions based on either simplified methods or response history analysis. Applications of the new configurations are briefly descri bed.