Stability Coefficient Table

Stability Coefficient is calculated at each story, and the status of acceptance is tabulated.

When "Story Shear Force Ratio>Consider Story Module" is checked in the "Model/Building/Control Data", accurate shear forces can be obtained for the story having the overlapping Module.

When Modules are defined in Structure > Building > Story > Define Module button, the Module data is displayed in the first column of the table.

"Story Shear Force Ratio" in "Model/Building/Control Data" must be checked for this function, which is checked as the Default.

Table Tool in midas Gen offers a variety of powerful built-in functions. Refer to Usage of Table Tool for detail directions.

From the Main Menu select Results > Tables > Result Tables > Story > Stability Coefficient Table

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

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

Stability Coefficient Parameters

Deflection Amplification Factor(Cd): It is applied to the calculation of Modified Story Drift.

Importance Factor(Ie): It is applied to the calculation of both Modified Story Drift and Stability Coefficient.

Scale Factor: Cm, Scale-up Factor. It is applied only to the response spectrum load cases or load combinations containing response spectrum load cases based on ASCE7-10, "12.9.4 Scaling Design Values of Combined Response". It will not be applied to Static Seismic Load Cases.

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.

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 ad X Scale Factor X Cd / Ie

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 Modified Story Drift X Ie) / (Story Shear Force X Height )

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 Structure > Building > Story > Define Module button