SAP2000 SAP2000 Web Tutorial 1

Note: The damping ratios must be between 0 and 1. A value of 5% of critical
damping should be entered as 0.05, not 5.
• The Show Single Demand Spectrum (Variable Damping) check box is checked indicating
that the single demand spectrum is shown on the plot. The color box adjacent to the
Show Family of Demand Spectra check box is yellow (by default) indicating that the
single demand spectrum is shown in yellow. You can change the color by clicking on the
color box.
Note: The single demand spectrum (variable damping) curve is constructed by doing
the following for each point on the ADRS pushover curve:
1. Draw a radial line
through the point
on the ADRS
pushover curve.
This is a line of
constant period.
2. Calculate the
damping
associated with the
point on the curve
based on the area
under the curve up
to that point.
Sa
Sd
Radial line has constant period
Point on single demand spectrum
(variable damping) associated with
arbitrary point on pushover curve
Pushover curve
Demand spectrum plotted at same
damping level as associated with
arbitrary point on pushover curve
Arbitrary point on pushover curve
Damping based on area under pushover
curve up to arbitrary point
3. Construct the demand spectrum, plotting it for the same damping level as
associated with the point on the pushover curve.
4. The intersection point of the radial line and the associated demand
spectrum represents a point on the Single Demand Spectrum (Variable
Damping) curve.
This method is similar to the method called Procedure B in Chapter 8 of ATC-40
except it does not make the simplifying assumption that the post yield stiffness
remains constant. It is essentially the method referred to as “exact” in the
discussion of the method called Procedure C in Chapter 8 of ATC-40.
• The Show Constant period Lines At check box is checked indicating that up to four
different constant period lines are shown on the plot. The color box adjacent to the Show
Constant period Lines At check box is gray (by default) indicating that the constant
period lines are shown in gray. You can change the color by clicking on the color box.
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