Learning Forum

[lborroto]

Hi all,

I would like to ask one question about bolt data extracted after subsequent analysis:

Is is correct to evaluate pre-stressed bolts (modeled as beams) in a response spectrum analysis preceded by static (bolt pre-stress is applied here) and a modal analysis that feeds response spectrum analysis?

I have a model following the above procedure but the stresses I get on the bolts are lower than what they were after the first static analysis.

I got the beam results in response spectrum through available solutions quantities from the worksheet and defined results expressions.

For example:

= BEAMDIRECT

= BEAM_AXIAL_FX

= BEAM_SHEAR_FSUM

all the above for Item Type: Element Name IDs and Solver Components ID's = 188

Thanks!

Lino

[peteroznewman]

Hi Lino The static structural model provides a pre-stress solution to the modal analysis to adjust the stiffness matrix to make add the stiffening that the loads provide, but don't apply the loads in the downstream response spectrum analysis, so there are no stresses in the beams that the preload would have created. It's just that the stiffness of the beam has been increased by the tension.
Therefore the results you obtained in the response spectrum are what I would expect. You can add the stress results from the static structural bolt pretension to the stress results from the response spectrum to get the total stress.
Regards Peter

[lborroto]

Hi Peter Thank you for the answer, can you add a bit more to the last part?
When you say add the stress results to get the total stress, you mean combining static and response spectrum results in workbench?
Regards Lino