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ASCE 7-16 Guidance
In the past, codes took a silent approach and did not provide guidance on spectral matching.
ASCE/SEI 7-16, Minimum Design Loads and Associated Criteria for Buildings and Other Structures, was the first code to offer guidance on using spectral matching in section 16.2.3.3. According to section 16.2.3.3, Ground motion pairs may be spectrally matched such the suite mean of their RotD100 (maximum rotated component) equals or exceeds 110% of the defined target spectrum over the specific period range. This imposed a 10% penalty on spectral matched records compared to scaled records. It may be argued that this penalty should not applied to suites spectrally matched using the Mean spectral matching method, since this method preserves the dispersion in scaled record suites.
Vertical components may be matched in case vertical response is required in the analysis such that the matched vertical components may not fall below the target vertical spectrum. [2]
Period Range
In general, the codes generally require the same period range for spectral matching as for scaling. However, the user may want to use a wider period range in order to ensure that the resulting spectra satisfy the code requirements of the period range. Using a wider frequency/period range may also result in better overall spectral match and may provide better convergence behavior of the algorithm.
Table: Period range according to different codes
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Code
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Section
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Lower Bound Period
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Upper Bound Period
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ASCE/SEI 7-16 [2]
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16.2.3.1a (Regular Structures)
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0.2T
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1.5T
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ASCE/SEI 7-16 [2]
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18.2.2.2b (Damping Structures)
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0.2T1D
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1.25T1M
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ASCE/SEI 7-10 [3]
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16.1.3.1 (Regular Structures)
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0.2T
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1.5T
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ASCE/SEI 41-17 [5]
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2.4.3 (Regular Structures)
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0.2 Tmin
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1.5 Tmax
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ASCE/SEI 41-17 [5]
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14.2.2.1 (Isolated Structures)
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0.75Tx
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1.25Tx
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ASCE/SEI 41-13 [6]
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2.4.2.2b (Regular Structures)
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0.2T
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1.5T
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a If the vertical component is taken into consideration, the lower bound period used for modification of vertical components of ground motion should be the maximum of :
•0.1 seconds
•Lowest period at which significant vertical mass participation occurs.
b The response spectrum of one component of the pair is at least 90% of the corresponding ordinate of the response spectrum used in the design.
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