Analysis Types and Analysis Codes in the DO File

DO is a generic term for Displacement Output file. The displacement output file contains nodal results (as opposed to element results) depending on the analysis type.

The first load case (or time step or mode shape) in the DO file is either 1 or 0 depending on the analysis type, with a total of LC load cases. For example, a Linear Static Stress with three load cases would be numbered 1, 2, 3. An MES analysis with three load cases (or time steps) would be numbered 0,1,2. The actual load case number is not stored in the DO file. The load case number is implied based on the analysis type and first load case number.

Analysis Type	Extension of file	Load Cases	Analysis Code
Nonlinear mode shape	.amo	0 to LC-1	1 *
Buckling displacement	.do6	1 to LC	1 *
DDAM displacement	.dod	1 to LC	13
Electrostatic voltage	.vo	1 to LC	10 *
Frequency Response displacement	.do5	1 to LC ⁽³⁾	-5
Linear Mode shape	.mo	1 to LC	1 *
Linear Static Stress displacement	.do	1 to LC	0 *
Linear Static Stress reactions	.ro	1 to 3xLC ⁽¹⁾	0 *
Load Stiffening Modal displacement	.mo8	1 to LC	1 *
MES/Nonlinear Stress displacement	.ado	0 to LC-1	4 *
MES/Nonlinear Stress reactions	aro	0 to LC-1	4 *
MES/Nonlinear Stress reactions	.do7	1 to LC	7
Response Spectrum displacement	.do3	1 to LC ⁽²⁾	3
Steady State Heat Transfer	.to	1 to LC	10*
Transient Heat Transfer	.tto	1 to LC or 0 to LC-1depending on version	11
Transient Stress accelerations	.ao4	1 to LC	4 *
Transient Stress displacement	.do2 or .do4	1 to LC	2 * or 4 *

* The analysis code is an integer written to the header of the DO file, and it loosely indicates the analysis type. When the existing results file is a binary file, the contents of the DO file are known from the extension (provided you have not changed the extension). When the existing results file is a text file, the contents can only be guessed from the analysis code (or determined directly from the Existing Results File given if the Nodal Results Translator created the file, provided you have not changed the extension). If the analysis type is based solely on the analysis code in the header, the following items are not known for those analysis codes marked with an asterisk (*) in the table:

what default extension to propose for the New Results File
whether the six degree of freedom values are displacements, velocities, or something else
whether the load cases in the results represent load case 1 through LC, or 0 through LC-1
whether the cases are load cases, time steps, or mode shapes.

In these situations, the labels may not be accurate, but the translation will work.

⁽¹⁾ The load cases for a linear static stress reaction force results are in groups of three, as follows:

load case 1, 4, 7, [3x(n-1)+1] element reaction for load case n
load case 2, 5, 8, [3x(n-1)+2] applied forces for load case n
load case 3, 6, 9, [3x(n-1)+3] support reactions for load case n

When the existing file is a binary format, the load case list on the Load Case and Node Output tab will also show the load case number (1 through 3x(n-1)+3) and the corresponding result load case number n.

⁽²⁾ The load cases for a response spectrum analysis are as follows:

For the Original Procedure, LC = Nfreq+1. Load cases 1 through Nfreq correspond to the response of the model at each of the Nfreq natural frequencies. The last load case is the resultant SRSS.

For the NRC Reg. Guide 1.92 and Modified Procedure, LC = (n directions)*(Nfreq)+1 where (n directions) is the number of directions that the spectrum is applied in, and Nfreq is the number of natural frequencies. The results are in the following order, where any result is not written to the results file if the model is not loaded in that direction:

Load Case	Result
1	mode 1, spectrum in X direction
2	mode 2, spectrum in X direction
...	...
Nfreq	mode Nfreq, spectrum in X direction
Nfreq+1	mode 1, spectrum in Y direction
Nfreq+2	mode 2, spectrum in Y direction
...	...
2*Nfreq	mode Nfreq, spectrum in Y direction
2*Nfreq+1	mode 1, spectrum in Z direction
2*Nfreq+2	mode 2, spectrum in Z direction
...	...
3*Nfreq	mode Nfreq, spectrum in Z direction
last = (n directions)*(Nfreq)+1	resultant of all load cases

(3) The load cases for a frequency response analysis depend on the number of exciting frequencies n (not the natural frequencies). The results are in the following order:

Load Case	Result
1	in phase result at forcing frequency 1
2	in phase result at forcing frequency 2
...	in phase result at forcing frequency ...
n	in phase result at forcing frequency n
n+1	out of phase result at forcing frequency 1
n+2	out of phase result at forcing frequency 2
...	out of phase result at forcing frequency ...
2*n	out of phase result at forcing frequency n
2*n+1	SRSS result at forcing frequency 1
2*n+2	SRSS result at forcing frequency 2
...	SRSS result at forcing frequency ...
3*n	SRSS result at forcing frequency n