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4.1.8.11.(5)
ApplicationIntent
OS2OP2
ObjectiveOS2 Structural Safety
Attribution
[F20-OS2.1]
Application
Application 1: 
Determination of the higher mode factor, Mv, and the associated moment reduction factor at the base of the structure, J.
Exceptions: 
except as stated in Sentence 4.1.8.1.(1), which applies to areas where the spectral response acceleration amplified for site conditions equals the floor levels found in low seismicity regions with Site Class C (i.e. very dense soil and soft rock).
This applies to buildings described in Sentence 1.3.3.2.(1) of Division A and to buildings to which Part 9 applies [see Sentence 1.3.3.3.(1) of Division A for application of Part 9] that are required to be designed in accordance with the requirements of Part 4.
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Intent
Intent 1: 
To limit the probability that the calculation of the equivalent static base shear will not take into account the participation of higher modes in the dynamic response of the structure by the inclusion of the factor Mv, which could lead to structural failure, which could lead to harm to persons.
Intent 2: 
To modify the calculation for the overturning moment at the base of the structure, on the basis that the higher modes included in the base shear do not contribute significantly to the base overturning moment.
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