Irregularity Check Parameter

To select calculation method for story irregularity check

From the Main Menu select Results > Result Tables > Story > Irregularity Check Parameter

Select Result Tables > Story > Irregularity Check Parameters in the Tables tab of the Tree Menu.

From Record Activation Dialog, select the load cases/combinations for which Stability Coefficient will be calculated and P-Delta effect will be considered.

Record Activation dialog box

Refer to Usage of Table Tool and check the following data:
 

When Modules are not defined

Load Case: Unit load case/Combination

Story: Story number

Height: Story (floor to floor) Height

1. Vertical Load

Sum of all the vertical loads of upper story levels is used for calculating Stability Coefficient.

2. Story Shear Force

Story shear force due to the selected Load Case

3. Modified Story Drift

Modified Story Drift = Story Drift X Response Modification Factor (RMF) X Scale up Factor

4. Beta(β)

β: Design Shear Force/Shear Capacity at a story in question.  If it is not calculated, β=1 is used.

5. Stability Coefficient(Θ)

Stability Coefficient(Θ) = ( Vertical Load X Story Drift) / (Story Shear Force X Height X Cd )

6. Allowable limit

Stability Coefficient(Θ) limited by the standard is printed.

Allowable limit = 0.5 / (Beta X Cd ) ≤ 0.25

7. Remark

If Θ is less than 0.1, "OK" is printed.

If Θ exceeds 0.1 and is less than the Allowable limit, "P-Delta Req." is printed.

If Θ exceeds the Allowable limit, "Redesign" is printed.

8. P-Delta Incremental Factor(ad)

For those stories marked with "P-Delta Req." under Remark, Incremental Factor for P-Delta effect is calculated.

When Modules are defined

The Module column is generated only when the Modules are defined. Stability Coefficients are calculated as per the following Note.

Note

Stability Coefficients for the top floors of each Module are not generated.

Module: Module name is defined in Define Module

Load Case: Unit load case/Combination

Story: Story number

Height: Story (floor to floor) Height

1. Vertical Load

Sum of all the vertical loads of upper story levels is used for calculating Stability Coefficient.

2. Story Shear Force

Story shear force due to the selected Load Case

3. Modified Story Drift

Modified Story Drift = Story Drift X Response Modification Factor (RMF) X Scale up Factor

4. Beta(β)

β: Design Shear Force/Shear Capacity at a story in question.  If it is not calculated, β=1 is used.

5. Stability Coefficient(Θ)

Stability Coefficient(Θ) = ( Vertical Load X Story Drift) / (Story Shear Force X Height X Cd )

6. Allowable limit

Stability Coefficient(Θ) limited by the standard is printed.

Allowable limit = 0.5 / (Beta X Cd ) ≤ 0.25

7. Remark

If Θ is less than 0.1, "OK" is printed.

If Θ exceeds 0.1 and is less than the Allowable limit, "P-Delta Req." is printed.

If Θ exceeds the Allowable limit, "Redesign" is printed.

8. P-Delta Incremental Factor(ad)

For those stories marked with "P-Delta Req." under Remark, Incremental Factor for P-Delta effect is calculated.

9. Context Menu

The user provides the data for calculating stability coefficients and P-Delta incremental factors.  These are required values for generating the table.  When Table is invoked, the set Story Drift Parameters window is executed first.

Context Menu (Set Stability Coefficient Parameter)

Stability Coefficient Parameter dialog box

Modify Beta dialog box

Deflection Amplification Factor

Importance Factor

Scale Factor: Cm, Scale-up Factor

Vertical Load Combination: Select a vertical loading condition for which P-Delta effect will be considered.

Define Beta: Selection of Beta values.  In case of User Define, values for each story can be directly entered.