Floor Diaphragm Masses

Function

When the model is a building, enter the floor mass data for stories.

There are two methods for entering floor masses.

Calculate and enter the floor mass, rotational mass moment of inertia and coordinates of the center of mass
When the floor plane is consisted of line masses (straight line, arc) or surface masses (rectangle, triangle, circle), the geometric shapes of the relevant mass units and the positions are specified. The program then automatically computes the floor mass, the rotational mass moment of inertia and the center of mass

The function can be repeatedly used for a given floor plane when the floor plane is consisted of several units of different shapes.

The entered mass data are used to automatically calculate equivalent static seismic loads according to the seismic design codes and used for dynamic analysis.

Floor Diaphragm Masses is used in connection with Model > Building > Story, Control Data.

In order to use the function, the Z-axis of the building model must orient opposite to the gravity direction, and "Consider Floor Diaphragm" in Story must be assigned to the relevant floors to activate Rigid Diaphragm Action for each story.

The calculated or entered mass data are automatically entered at the Diaphragm Centers, that is, the center of mass is auto-calculated for each story. Only the components in the GCS x and y directions and the rotational mass moment of inertia about the z-axis are considered.

Call

From the Main Menu select Model > Masses > Floor Diaphragm Masses.

Select Geometry > Masses > Floor Diaphragm Masses in the Menu tab of the Tree Menu.

Entry

Mass Type

Select the type of mass to be entered.

Point Mass

Line Mass

Circular Arc Mass

Circular Area Mass

Triangular Area Mass

Rectangular Area Mass

Start Story/End Story

Assign the stories to enter masses.

Diaphragm Mass

Point Mass

Mp : Point mass in GCS X, Y-directions (Translational Mass)

Mr : Rotational Mass Moment of Inertia about GCS Z-direction at the point mass position

Xc, Yc : GCS coordinates of the center of the point mass

Line Mass

Ml : Mass per unit length (Mass/Length)

D1 : Length of line mass

Xc, Yc : GCS coordinates of the center of the line mass

Circular Arc Mass

Ml : Mass per unit length (Mass/Length)

Xc, Yc : GCS coordinates of the center of the circular arc volume

D1 : Angle of the circular arc (Degree)

D2 : Radius of the circular arc

D3 : Angle of inclination from the center of the circle to the center of gravity of the circular arc relative to GCS X-axis (Degree)

Circular Area Mass

Ma : Mass per unit area (Mass/Area)

Xc, Yc : GCS coordinates of the center of the circle

D1 : Internal angle of the arc strip area (Degree)

D2 : Radius of the arc strip area

D3 : Radial strip width

D4 : Angle of inclination from the center of the circle to the center of gravity of the arc strip area relative to GCS X-axis (Degree)

Triangular Area Mass

Ma : Mass per unit area (Mass/Area)

X1, Y1 : Coordinates of a corner of the triangular area

X2, Y2 : Coordinates of the 2nd corner of the triangular area

X3, Y3 : Coordinates of the 3rd corner of the triangular area

Rectangular Area Mass

Ma : Mass per unit area (Mass/Area)

Xc, Yc : GCS coordinates of the center of the rectangular area

D1 : Length of one edge of the rectangular area

D2 : Length of the other edge of the rectangular area perpendicular to D1

Note

When Floor Diaphragm is considered, mass center can be checked from Query>Story Mass Table.