## 09

Notes:

1. The substructure design forces resulting from the elastic analysis divided by the appropriate R-factor for SDAP E can not be reduced below 70% at the R-factored reduced forces or the 50% PE in 75-year design forces as part of the pushover analysis.

2. There may be design situation (e.g., architecturally oversized column) where a designer opts to design the column for an R = 1 (i.e., elastic design). In concrete columns the associate elastic design shear may be obtained from the elastic analysis forces using an R-factor of 0.67 or by calculating the design shear by the capacity design procedures using a flexural overstrength factor of 1.0. In steel-braced frame if an R = 1.0 is used the connection design forces shall be obtained using an R = 0.67. If an R = 1.0 is used in any design the foundation shall be designed for elastic forces plus the SDR detailing requirements are required for concrete piles (i.e., minimum shear requirements).

3. Unless specifically stated, the R-factor applies to both steel and concrete.

4. N/A means that owners approval is required and thus the use of SDAP E is required.

where RB is the base response modification factor specified in Table 20.8, T is the natural period of the structure, T* = 1.25 Ts where Ts is as defined in Section 20.6.1.1.

For connections (superstructure to abutment; expansion joints within a span of the superstructure, columns, piers, or pile bents to cap beam or superstructure; and column or piers to foundations), an R-factor of 0.8 shall be used for those cases where capacity design principles are not used to develop the design forces to design the connections. It is assumed that if the R< 1.5, columns should remain essentially elastic for design earthquake; if 1.5 <R > 3.0, columns should be repairable; if R > 3.0 significant plastic hinging may occur and the column may not be repairable; however, collapse is still prevented.

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