Use the Parameters for ATC 40 Capacity Spectrum form to specify the parameters for displaying pushover curves in accordance with ATC 40 guidance.
Name edit box. The program will suggest a default name. Use this name or type a new one in this edit box.
Units drop-down list. Use the units displayed or select another from the list; the units displayed will be used on the plot of the pushover curve.
Plot Axes area. Choose the plot axes as Sa-Sd (spectral acceleration vs spectral displacement), Sa-T (spectral acceleration vs period) or Sd-T (spectral displacement vs period).
Set Axis Data button. Click this button to access the Override Axis Labels and Range form. Use the options on that form to change the minimum and maximum horizontal and vertical ranges and the axis labels for the curve.
Demand Spectrum Definition. Choose to define the demand spectrum based on a function or user specified coefficients.
Function option, drop-down list, and SF (Scale Factor) edit box. When this option is selected, choose a previously defined spectrum function from the drop-down list and use the default scale factor or use the edit box to specify the SF.
Use Coeff and Ca and Cv (Seismic Coefficient) edit boxes. The shape of the demand spectrum with 5% damping is controlled by the values input in the Ca and Cv (Seismic Coefficient) edit boxes. Refer to ATC-40, Chapter 4, for an explanation of, and appropriate values for, Ca and Cv. The default value for both Ca and Cv is 0.4. Demand spectra for other damping levels are created from the 5% damped spectrum using the spectral reduction factors described in Section 8.2.2.1.1 of ATC-40.
Damping Parameters Definition.
Inherent + Additional Damping edit box. In the Damping Parameters area, type a value in the Inherent/Additional Damping edit box. The value input into this box must be between 0 and 1, inclusively. The default value is 0.05. Referring to ATC-40 equation 8-8, the b0 term is automatically included by the CSiBridge analysis method, and the 5% inherent viscous damping term can be specified in the Inherent/Additional Damping edit box as 0.05. If additional viscous damping is provided in the structure, perhaps by viscous dampers that are not specifically included in the model, this damping should also be included in the Inherent + Additional Damping edit box. Thus if the damping inherent in the structure is assumed to be 5% of critical damping, and dampers that provide an additional 7% of critical damping are assumed to be added to the structure (although they are not actually in the model), the value input in the Inherent + Additional Damping edit box should be 0.12, since 0.05 + 0.07 = 0.12.
Structural Behavior Type. Select one of the four Structural Behavior Type options in the Damping Parameters area. The Structural Behavior Types A, B and C default to the values defined for those structural behavior types in Section 8.2.2.1.1 of ATC-40 .
User option - Modify/Show button. The User option allows the user to input kappa (k) values other than those provided by behavior Types A, B, and C. With the User option selected, click the associated Modify/Show button to display the Override Structural Behavior Type form.
Items Visible On Plot area. Choose the items to be displayed on the plot.
Show Capacity Curve check box. Checking this check box will show the capacity curve on the plot.
Color. The default color for the capacity curve is green. Click the color box to display the Color form and change the color of the capacity curve.
Show Family of Demand Spectra check box. Checking this check box overlays a family of demand spectra on the capacity curve in the ADRS format.
Color. The default color for the family of demand spectrum curves is red. Click the color box to display the Color form and change the color of the demand spectra.
Damping Ratios. The family of curves can include up to four demand spectra curves, each with a different effective damping ratio, beff. By default, the program plots curves with beff = 0.05, 0.1, 0.15 and 0.2. The damping ratios for any of the four curves can be changed by editing the value in one of the four Damping Ratios, beff edit boxes. The values input into the beff edit boxes must be between 0 and 1, inclusively. A value of 0, or a blank edit box, means to omit that demand spectrum curve.
Show Single Demand Spectrum (ARDS) (Variable Damping). Check the Show Single Demand Spectrum (Variable Damping) check box to display the demand spectrum as a single curve.
Color. The default color for the single modified demand spectrum curve is yellow. Click the color box to display the Color form and change the color of the demand spectrum.
The family of demand spectra and the single demand spectrum (variable damping) can be displayed at the same time, or they can be displayed separately.
Show Constant Period Lines At check box. Check the Show Constant Period Lines At check box to display lines of constant period. These lines appear as radial lines on the capacity spectrum plot. By default the program plots lines for T = .5, 1, 1.5 and 2 seconds. The periods for any of the four curves can be changed by editing the value in one of the four associated edit boxes. A value of 0, or a blank edit box, means to omit that period line.
Color. The default color for the period lines is gray. Click the color box to display the Color form and change the color of the period lines.
Reset Default Colors button. Click the Reset Default Colors button to reset all of the colors to the defaults.
|
Access the Parameters for ATC 40 Capacity Spectrum form as follows: Method 1 - This method can be used to specify parameters for displaying a pushover curve before a static nonlinear analysis has been run.
Method 2 - Use this method to display a pushover curve after an analysis has been run.
Method 3 - Use this method to save the parameters specified for displaying a pushover curve as a Named Set for reuse in the future.
|