THE IMPORTANCE OF CONSIDERING SPECTRAL SHAPE WHEN EVALUATING BUILDING SEISMIC PERFORMANCE UNDER EXTREME GROUND MOTIONS

Recent research has shown that considering ground motion spectral shape is important when using nonlinear dynamic analysis to predict seismic structural response under extreme ground motions (such as a 2% in 50 year of Maximum Considered Earthquake motion). Using a 20-story reinforced concrete frame building, this paper presents quantitative comparisons of interstory drift predictions using 10 ground motion selection methods, some of which are based on building code methods, while the other methods more carefully account for the proper spectral shape associated with high-amplitude ground motions. To gauge prediction accuracy, the individual predictions are then compared to a “high-end prediction” which is based on a large number of structural analyses. The findings show that methods that account for appropriate spectral shape lead to accurate response predictions (over-prediction of 1% or 6%, depending on method) and the building code methods result in 30% to 60% over-prediction of response relative to the other methods.