How to find max bending moment Mz caused by a moving load in staad pro 1

[pedershaab]

I am just a beginner in staad pro.
After applying a moving load on a beam, I want to find exact the position on that beam which has maximum bending moment Mz caused by that moving load. (If I go to post-analysis, the beam is divided into 12 sections and I can only find position of max bending moment among those sections, not the exact one).
Any of your advice will be very much appreciated.
Thank you

 

[structuresguy]

You can define more sections to analyse for the beams; 12 sections is staad default (which i find adequate most of the time). Staad always only checks loads/stresses for beams at discreet sections. You would need to use the Section command (section 5.40 in the manual) to define more sections along the length of the beam, it terms of fractional member lengths. It is tedious, but you could define as many sections as you want Staad to check. Then you need to define parameter under the design tab to force staad to use those custom sections.

Also, with moving loads, how often did you increment the load position? This could also affect finding max moments. I usually do moving loads incremented to 1 foot intervals.

 

[pedershaab]

Thank you very much for you reply.
I have followed your instruction above. But I could not force staad to use my custom-defined sections. Can you please have a brief look at the commands below and tell me what was not correct (this is just a test problem, the force and sections were selected arbitrarily, it has no meaning in realty).
----------------------------------
STAAD PLANE
START JOB INFORMATION
ENGINEER DATE 01-Jul-09
END JOB INFORMATION
INPUT WIDTH 79
UNIT FEET KIP
JOINT COORDINATES
1 0 0 0; 2 8 0 0;
MEMBER INCIDENCES
1 1 2;
DEFINE MATERIAL START
ISOTROPIC STEEL
E 4.176e+006
POISSON 0.3
DENSITY 0.489024
ALPHA 6.5e-006
DAMP 0.03
END DEFINE MATERIAL
MEMBER PROPERTY AMERICAN
1 TABLE ST W5X16
CONSTANTS
MATERIAL STEEL ALL
SUPPORTS
1 2 PINNED
DEFINE MOVING LOAD
TYPE 1 LOAD 1 1
DIST 2
LOAD GENERATION 7
TYPE 1 0 0 0 XINC 1
PERFORM ANALYSIS
PRINT SECTION DISPL LIST 1
SECTION 0 0.1 0.2 0.3 1 ALL
SECTION 0 0.4 0.5 0.6 1 ALL
SECTION 0 0.7 0.8 0.9 1 ALL
PARAMETER 1
CODE AISC
BEAM 0 ALL
PRINT SECTION DISPL LIST 1
FINISH
----------------------------------
Thank you

 

[structuresguy]

Sorry, I think I may have led you down the wrong path a little. In general, you would not need to define custom sections just to find max moment or shear. Staad's figures out the moments/shears along the length of the beam automatically, but only DESIGNS (checks stress levels) them at 12 sections along the length. So unless you need to find moment and shear at a specific location, or force it to design only at specific locations, you should not need to worry about custom sections.

That said, in order to see the forces at your custom sections, you need to add a "print section force" command to your input file. Then you will see the forces at your specific sections in the output file.

Otherwise, if you are just looking to see max shear and max moment, and/or shear/moment diagrams along the length of teh beam, there are several ways to do this. In post processing, you can go to the Beams:Graphs tab, and then see the shear, moment, and axial load distribution along hte length of the selected member. It will then tell you the location of max value in the graph.

You could also go to the Beams:Forces tab, and see this info in tabular format.

And if you add a load envelope (or multiple envelopes), you can see the same results for the envelope on the graphs.

I attached a couple files showing screen shots on the graphs, and envelope screen.

 

[structuresguy]

here is the graphs display

 

[structuresguy]

here in teh envelope screen.

Also, here is your input file with the extra bits i added for a load envelope and print forces. Hope this helps some.

STAAD PLANE
START JOB INFORMATION
ENGINEER DATE 01-Jul-09
END JOB INFORMATION
INPUT WIDTH 79
UNIT FEET KIP
JOINT COORDINATES
1 0 0 0; 2 8 0 0;
MEMBER INCIDENCES
1 1 2;
DEFINE MATERIAL START
ISOTROPIC STEEL
E 4.176e+006
POISSON 0.3
DENSITY 0.489024
ALPHA 6.5e-006
DAMP 0.03
END DEFINE MATERIAL
MEMBER PROPERTY AMERICAN
1 TABLE ST W5X16
CONSTANTS
MATERIAL STEEL ALL
SUPPORTS
1 2 PINNED
DEFINE MOVING LOAD
TYPE 1 LOAD 1 1
DIST 2
LOAD GENERATION 7
TYPE 1 0 0 0 XINC 1
PERFORM ANALYSIS
DEFINE ENVELOP
1 TO 7 ENVELOP 1
END DEFINE ENVELOP
PRINT SECTION DISPL LIST 1
SECTION 0 0.1 0.2 0.3 1 ALL
SECTION 0 0.4 0.5 0.6 1 ALL
SECTION 0 0.7 0.8 0.9 1 ALL
PARAMETER 1
CODE AISC
BEAM 0 ALL
PRINT SECTION DISPL LIST 1
PRINT SECTION FORCES
FINISH

 

[SteveGregory]

For maximum forces you may not need to subdivide the members or use the section command. Try the PRINT MAXFORCE ENVELOPE NSECTION 48 LIST command.