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Seismic Testing and Analytical Studies for the Development of New Seismic Force Resisting Systems for Metal Buildings

  • Author(s): Smith, Matthew Douglas
  • et al.
Abstract

Metal buildings (MB) are a prevalent form of low-rise construction in the U.S. They are built in a variety of geographic locations, including high seismic regions. It is desirable to understand the seismic performance of such a prevalent structural system. There is a general lack of experimental data available concerning the seismic performance of metal buildings and the web-tapered I- shaped beams of which they are typically composed. In order to improve the seismic performance of the moment resisting frames in these buildings new Seismic Force Resisting Systems (SFRS) need to be developed. But first, several key issues required research. The MB moment frames are often controlled by lateral-torsional buckling (LTB) and current design methodologies do not provide adequate LTB flexural strength prediction equations for the full range of member geometries commonly used. Single-story MB frames deviate significantly from the buildings used to define approximate fundamental period equations in the current building codes and the applicability of those equations to MB frames is questionable. Partial-floors, called mezzanines, are often attached to MB frames, yet no clear guidance is given in the current building codes to address the seismic analysis and design of these structures. Finally, experimental data for the dynamic characteristics of MB moment frames at the system level and their cyclic post-buckling behavior at the member level was needed. This research provided experimental data through two testing programs. Shake table testing was performed on two full-scale metal buildings. Results of those tests led to two concepts for new SFRS for MB frames, one of which relies on LTB for inelastic hinging. Experimental data was provided in support of the development of the new SFRS through cyclic tests of ten web-tapered rafter specimens. The cyclic performance of LTB was investigated and results used to outline a new design procedure. In addition, new approximate period equations and seismic design methods for mezzanines were developed. This research provides the necessary foundation for the development of new SFRS for MB moment frames which considers the available ductility of web-tapered rafters

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