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Why are the subtitles colored red in this chapter?
In the table, state the name of each code section (instead of the name, you may describe the chapter and/or applicability of recommendation, for example some apply to dampers, base isolation, etc.). You may also add it to the code column similar to the way you added "Far-Field" and "Near-Field"
Both ASCE 41-13 lines should include footnote 2 reference
It would be better to use letters for the footnotes in the two tables (a, b, c instead of 1, 2, 3)
In 41-17, you only show the period range for base-isolated structures, but not for regular structures (or damped)
I believe the section on "Ground Motion Scaling" refers to ASCE 7-16. Why discuss that code specificially? We can argue it's the current code, but I think you should clarify th this is the 7-16 version.
We should also probably refer to the section on "Record Rotation Code Requirements"
Required Number of Ground Motions
Usually, ground motion records consist of pairs of orthogonal horizontal ground motions components. Ground motions may also include a vertical ground motion component that can be used when required in the analysis. The selection of ground motions should generally satisfy the following:
•Ground motion records should be selected from events within the same general tectonic regime
•Consistent magnitudes and fault distances as those controlling the target spectrum
•Have similar spectral shape to the target spectrum
Different codes have slightly different requirements for the required number of ground motion records and the method of scaling those records to the target spectrum. The following tables illustrates the requirements of various US Codes.
Table: Required number of ground motions by Code
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Code
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Section
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Number of GM Pairs
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GM Sa Measure
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GM Level
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Scaling Instructions
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ASCE/SEI 7-16
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16.2.2
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11
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Max Direction
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MCER
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MaxRot > 0.9x Target Spectrum
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ASCE/SEI 7-16
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18.2.2.21
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7
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Max Direction
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MCER
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|
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ASCE/SEI 7-10 Far-Field Provisions
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16.1.3
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7 (Avg) or
3 (Max)
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Max Direction
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2/3 MCER
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SRSS > Target Spectrum
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ASCE/SEI 7-10
Near-Field Provisions
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16.1.3
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7 (Avg) or
3 (Max)
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Max Direction
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2/3 MCER
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Average of FN > Target Spectrum
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ASCE/SEI 7-05
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16.1.3
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7 (Avg) or
3 (Max)
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Geomean
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2/3 MCE
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SRSS > 1.17x Target Spectrum
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ASCE/SEI 41-17
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14.2.2.1
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7
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Max Direction
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BSE-2N,BSE-1N, BSE-2E, BSE-1E
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MaxRot > 0.9x Target Spectrum
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ASCE/SEI 41-13
Far-Field Provisions
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2.4.2.22
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10 (Avg) or
3 (Max)
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Max Direction
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BSE-2N, BSE-1N
BSE-2E, BSE-1E
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SRSS > Target Spectrum
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ASCE/SEI 41-13
Near-Field Provisions
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2.4.2.2
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7x2 (Avg) or
3x2 (Max)
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Max Direction
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BSE-2N, BSE-1N
BSE-2E, BSE-1E
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Average of FN > Target Spectrum
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ASCE/SEI 41-06
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1.6.2.2
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7 (Avg) or
3 (Max)
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Geomean
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BSE-2E, BSE-1E
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SRSS > 1.3x Target Spectrum
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1 According to section ASCE 7-16 section 18.2.2.2, design earthquake and MCER ground motion suites may each consist of at least seven pairs of horizontal acceleration components selected and scaled from individual recorded events that have magnitudes, fault distance, and source mechanisms that are consistent with those that control the design earthquake and MCER events.
For each pair of horizontal ground motion components, the square root of the sum of the squares (SRSS) spectrum may be constructed by taking the SRSS of the 5% damped response spectra for the scaled components (when amplitude scaling is used, an identical scale factor is applied to both components of a pair).
2 ASCE/SEI 41-13 imposed different criteria for the required number of ground motions for nonlinear dynamic analysis. This criteria included distance condition, method of computing the results and the performance objective. If the desired site is classified as a far-field (distance from fault > 5 km or 3 miles), then the generated records may not be rotated. However, if the site is classified as near-fault site, then the generated recorded ground motion pairs may be rotated.
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Period Range
Codes require the average of the suite spectra to match the target over a specified period range, which is generally a function of the structure's first period of vibration.
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
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16.2.3.11
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0.2T3
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1.5T
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ASCE/SEI 7-16
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18.2.2.22
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0.2T1D4
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1.25T1M5
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ASCE/SEI 7-10
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16.1.3.1 & 16.1.3.2
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0.2T
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1.5T
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ASCE/SEI 41-17
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14.2.2.1
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0.75Tx6
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1.25Tx
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ASCE/SEI 41-13
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2.4.2.22
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0.2T
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1.5T
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1 If the vertical component is considered, 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
2 The average of the SRSS spectra from all horizontal component pairs does not fall below the corresponding ordinate of the response spectra used in the design
3 The 0.2T requirement is now supplemented with an additional requirement that the lower bound also should capture the periods needed for 90% mass participation in both directions of the building
4 T1D = Effective period, in seconds, of the fundamental mode of vibration of the structure at the design displacement in the direction under consideration
5 T1M = Effective period, in seconds, of the fundamental mode of vibration of the structure at the MCER displacement in the direction under consideration
6 Tx = Effective period of the seismically isolated structure in seconds at the displacement Dx in the direction under consideration
Ground Motion Scaling
According to ASCE/SEI, section 16.2.3 permits ground motions to be amplitude scaled with reference to section to 16.2.3.2. The following criteria may be satisfied:
•Each horizontal ground motion pair, a maximum-direction spectrum may be constructed from the two horizontal ground motion components
•Both horizontal components may be scaled with an identical scale factor
•The average of the maximum-direction spectra from all ground motions generally matches or exceeds the target response spectrum over the specified period range
•The average of the maximum-direction spectra from all the ground motions may not fall below 90% of the target response spectrum for any period within the same period range.
•The vertical component of each ground motion may be scaled such that the average of the vertical response spectra envelops the target vertical response spectrum over the period range
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