Seismic retrofit of flexible steel frames using thin infill panels

Non-linear inelastic analyses are conducted to investigate how structural behavior is affected when thin infills of steel, low yield steel, or Shearfill fabric are used to seismically retrofit steel frames located in regions of low and high seismicity, namely New York City and Memphis. A typical three-bay frame extracted from an actual 20-story hospital building in New York City is considered for this purpose. Fully rigid and perfectly flexible frame connection rigidities are considered to capture the extremes of frame behavior. It is found that the use of even very thin steel infill panels can significantly reduce story drifts without significant increases in floor accelerations, and that low yield steel behaves slightly better than standard constructional grade steel under extreme seismic conditions but at the cost of some extra material. It is also concluded that Shearfill membranes may not have the necessary strength and stiffness to be an effective retrofit solution, unless a thick membrane having multiple layers can be constructed.