Story Mass Data
For models with rigid diaphragms, the mass data as calculated by the program is listed. For each level, this includes the level label, diaphragm number, the weight, the mass, mass moment of inertia, center of mass, eccentricity and whether the mass is to be combined with another diaphragm. If the user has specified different values than those calculated, the user specified values are also listed. It also indicates whether self mass from beams, columns, walls or slab\deck are included in calculated mass properties.
Note that if there is line or point loads with mass components defined and they stay outside of any diaphragm, or there are members that are not a part of any diaphragm and they have self-mass defined, the program calculates mass associated with these, and they are labeled as "None" story mass component.
This section also tabulates distributed masses for semirigid diaphragms. In addition, distributed nodal masses can be also included in the report for Semirigid diaphragms if Reports- Include Semirigid diaphragm nodal results command is activated. Otherwise, the report only shows a summary of total nodal masses for Semirigid diaphragms.
| Setting | Description |
|---|---|
| Weight | This is the weight of the diaphragm. |
| Mass | This is the mass of the diaphragm. |
| MMI | This is the mass moment of inertia. |
| Xm | This is the X-coordinate of the center of mass. |
| Ym | This is the Y-coordinate of the center of mass. |
| EccX | This is the distance from the center of mass, or eccentricity, that seismic story forces will be applied if specified as eccentric load cases, measured along the X-axis. The default is 5% of the diaphragm dimension. |
| EccY | This is the distance from the center of mass, or eccentricity, that seismic story forces will be applied if specified as eccentric load cases, measured along the Y-axis. The default is 5% of the diaphragm dimension. |
| Combine | Mass lumping\combining data for diaphragms are given separately in the report based on story and diaphragm numbers. It indicates whether or not the mass properties of the indicated diaphragm is lumped or combined to another diaphragm. None indicate the mass properties are not lumped; otherwise, it indicates diaphragm number with story label. |