Criteria - Redundancy Factor
RAM Frame calculates the so-called "redundancy factors" (also called "redundancy coefficients" or "reliability factors") for each of the seismic load cases. These factors, which can be used in the generated load combinations, give a quantitative indication of how heavily loaded a member is under a particular seismic load case. The Redundancy Factor dialog box is used to specify criteria items that are used to calculate these factors.
Redundancy factors calculation are available for IBC 2000 / IBC 2003 and UBC 1997. They cannot be used in generated load combinations in IBC 2006.
A reduction factor of 0.8 will be used for loads applied in the direction specified as having a dual structural system. This is specified using the Consider as Dual System command.
IBC requires that the area of each floor, Ai, be used in the formula for calculating the Redundancy Coefficient. The user is given the option of using the floor areas calculated by the program or of inputting a floor area directly. This second option would only be appropriate if all of the floor areas were approximately the same.
UBC requires that the area of the ground floor be used in the formula for calculating the Redundancy Factor. AB is the ground floor area of the building. The user is given the option of selecting a level whose calculated area is to be used in the formula or of inputting a floor area directly.
The maximum angle from parallel between adjacent bays for which a column is considered "common to two bays" is also specified in this dialog box.
- If it is found that there is only one diaphragm at a story, the program uses total story shear and total story area for each member at the story without checking that the member is connected to the diaphragm.
- If it is found that there are more than one diaphragm at a story, and
- If a member is found to be connected to a diaphragm at the story, the diaphragm area and total shear at this diaphragm are used for the member
- If a member is found to be not connected to any diaphragm at the story, the total story area and total story shear are used for the member
- If a member is found to be connected more than one diaphragm, the sum of all diaphragm areas and the sum of shears at these diaphragms are used for the member