Use of Permanent Magnets to Improve the Seismic Behavior of Light-Framed Structures
Light-framed wood structures generally have satisfied the life safety objective of the current seismic design approach. The main source of energy dissipation in such structures is the inelastic behavior of the connectors connecting framing and sheathing elements. Wood framed structures when subjecte...
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| Format: | Others |
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Virginia Tech
2014
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| Online Access: | http://hdl.handle.net/10919/42707 http://scholar.lib.vt.edu/theses/available/etd-05182005-135746/ |
| Summary: | Light-framed wood structures generally have satisfied the life safety objective of
the current seismic design approach. The main source of energy dissipation in such
structures is the inelastic behavior of the connectors connecting framing and sheathing
elements. Wood framed structures when subjected to strong ground excitations experience
structural and non-structural damage which may incur large repair/replacement costs or
may even render the structure out of service. Thus, it is very important to apply
techniques to mitigate the seismic response of the light-framed structures and avoid large
monetary losses.
It is proposed to use commercially available permanent magnets, incorporated in
the form of passive friction dampers, to dissipate a part of input energy induced due to
strong ground motions, thereby reducing the inelastic energy dissipation demand of the
lateral load resisting system. The force of attraction between the permanent magnet and
ferromagnetic material like steel was utilized to produce the required friction resistance. A
sliding wall configuration consisting of flexible permanent magnets and steel plates
sandwiched between the plywood sheets was analyzed for its effectiveness in mitigating
the response of a two story wood shear wall structure. The structural analysis program
SAP2000 was used to perform nonlinear dynamic analysis of the finite element models
generated using the meshing algorithms incorporated into â WoodFrameMeshâ . Nonlinear
link elements available in SAP2000 were used to model the friction between the flexible
magnet sheet and the steel plate. The effects of various modeling parameters on the
solution of the nonlinear analysis were studied so as to arrive at appropriate values to
represent the friction problem. Also the friction damped structure was analyzed to study
its forced and free vibration characteristics. Further, the responses of the friction damped
structure and the undamped structure were compared when subjected to different ground
accelerations. The response of the friction damped structure was also compared to that of
the structure in which the proposed friction dampers were replaced by normal shear walls.
A huge reduction in the response of the friction damped structure was observed when
compared to the response of the undamped structure. The friction damped structure was
also analyzed for different values of modal damping ratios. Over all about 60-80% of the
input energy was dissipated by friction damping in all the cases. The slip resistance of a
flexible permanent magnet sheet was also verified in the laboratory. Above all the
magnetic properties of commercially available permanent magnets and the effects of
strong permanent magnets on human health were also studied. === Master of Science |
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