TR.37.1 Linear Elastic Analysis

General Format

PERFORM  ANALYSIS (PRINT { LOAD DATA | STATICS CHECK | STATICS LOAD | BOTH | ALL } )

Without one of these analysis commands, no analysis will be performed. These ANALYSIS commands can be repeated if multiple analyses are needed at different phases.

The following PRINT options are available:

If the PRINT LOAD DATA command is specified, the program will print an interpretation of all the load data.
PRINT STATICS CHECK will provide a summation of the applied loads and support reactions as well as a summation of moments of the loads and reactions taken around the origin.
PRINT STATICS LOAD prints everything that PRINT STATICS CHECK does, plus it prints a summation of all internal and external forces at each joint. This option generates a large volume of output.
Note: Since PRINT STATIC LOAD generates voluminous output, the printing of summation of internal and external forces at each joint is done for structures which have less than 1,000 joints. If the structure has 1,000 joints or more, this printing will be skipped.
PRINT BOTH is equivalent to PRINT LOAD DATA plus PRINT STATICS CHECK.
PRINT ALL is equivalent to PRINT LOAD DATA plus PRINT STATICS LOAD.
The PRINT MODE SHAPES command may be added separately after the Analysis command if mode shapes are desired. Refer to TR.42 Print Specifications for using additional print specifications.

Notes

This command directs the program to perform the analysis that includes:

Checking whether all information is provided for the analysis;
Forming the joint stiffness matrix;
Checking the stability of the structure;
Solving simultaneous equations, and
Computing the member forces and displacements.
If a RESPONSE SPECTRUM, TIME LOAD, or GROUND MOTION is specified within a load case or the MODAL CALCULATION command is used, a dynamic analysis is performed.

Note: Due to the mechanisms used to include control/dependent systems, if the reactions on control nodes are not included in a statics check then an out of balance report may result. This can be avoided by adding a short stiff member from a control node to the support.

General Analysis Comments

STAAD.Pro allows multiple analyses in the same run. Multiple analyses may be used for the following purposes:

Successive analysis and design cycles in the same run result in optimized design. STAAD.Pro automatically updates changes in member cross-sectional sizes. Thus the entire process is automated.

Refer to Example 1 in the Getting Started & Examples manual for detailed illustration.
Multiple analyses may be used for load-dependent structures. For example, structures with bracing members are analyzed in several steps. The bracing members are assumed to take Tension load only. Thus, they need to be activated and inactivated based on the direction of lateral loading.

The entire process can be modeled in one STAAD.Pro run using multiple PERFORM ANALYSIS commands. STAAD.Pro is capable of performing a design based on the load combinations provided.

Refer to Example 4 in the Getting Started & Examples manual for detailed illustration.
You may also use Multiple Analyses to model change in other characteristics like supports, releases, section properties, etc.
Multiple Analyses may require use of additional commands like the SET NL command (TR.5 Set Command Specification) and the CHANGE command.
Analysis and CHANGE are required after UBC cases if the case is subsequently referred to in a Repeat Load command or if the UBC case will be re-solved after a Select command or after a Multiple analysis.