TR.32 Loading Specifications
This section describes the various loading options available in STAAD.Pro. The following command may be used to initiate a new load case.
General Format
LOADING i1 ( LOADTYPE a1 ) ( REDUCIBLE ) ( TITLE any_load_title )
Where:
Parameter  Description  

LOADING i1  any unique integer number (up to five digits) to identify the load case. This number need not be sequential with the previous load number.  
LOADTYPE a1  one of the following:

The words LOADTYPE a are necessary only if you intend to use the Automatic Load Combination generation tool in the graphic interface. For details, refer to the Auto Load Combination dialog.
The keyword REDUCIBLE should be used only when the loadtype is LIVE. It instructs the program to reduce –according to the provisions of UBC 1997, IBC 2000, or IBC 2003 codes– a floor live load specified using FLOOR LOAD or ONEWAY LOAD commands. For details, see TR.32.4 Area, Oneway, and Floor Load Specifications.
Under this heading, all different loads related to this loading number can be input. These different kinds of loads are described in the remaining subsections below.
Notes

For Mass Model Loading in Dynamics, it is strongly recommended that you read G.17.3.2 Mass Modeling and TR.31.8.3 Mass Model Using Reference Load. For the purpose of entering the mass distribution for the first dynamic load case, use the following sections:
A reference load can be used to create a mass model for all dynamic analyses.
The purpose of the mass modeling step is to create lumped masses at the joints that the eigensolution can use. The member/element loading is only a convenience in generating the joint masses. Analytically the masses are not in the elements but are lumped at the joints.
 The absolute value of joint loads or loads distributed to joints from member/element loadings will be treated as weights. The moments applied to member/elements or computed at joints as a result of member/element loadings will be ignored. Only moments (actually weight moment of inertia, forcelength^{2} units) applied in the Joint.
 The load command will be used in defining the weight moment of inertias at joints. For dependent joint directions, the associated joint weight or weight moment of inertia will be moved to the control. In addition, the translational weights at dependent joint directions will be multiplied by the square of the distance to the control to get the additional weight moment of inertia at the control. Crossproduct weight moment of inertias at the control will be ignored.
 When Y is set as "Up" (default), then the horizontal seismic loads act in
the global X and Y directions. The vertical seismic loads act in the global Y
direction.
When SET Z UP is used, then the horizontal seismic loads act in the global X and Z directions. The vertical seismic loads then act in the global Z direction.