Pile convergence check vs. Superelement 1

[ART0461]

We are using SACS computer software for designing fixed offshore platforms. On pile convergence check for a certain platform, we found difficulty to achieve pile convergency to an acceptable level (deviation below 10% for pile rotation & deflection between Post and single Pile run). Our client suggests to use Superelement. We are not familiar with the method. Can anybody explain what is this or what is the difference with pile stubs for convergence check ? Another question, is it more conservative ?
Thank's in advance for any information.

 

[GraemeL]

I take it you have looked at the section, Section 6.6 "Trouble Shooting Common Problems" in the "SACS PSI/PILE Users Manual"? This .pdf file is accessed through the SACS Executive.

There are listed various options or common modelling glitches that cause a pile problem to not converge.

The SUPERELEMENT part of SACS used to be used to model part elements of an overall structure as a stiffness matrix so to reduce the size of the SACS model. This originated in the days when computing power was more limited. Nowadays with the Release 5 and upwards of SACS, model sizes are unlimited and high speed processors mean very complicated models take only a short time to run. Hence SUPERELEMENT tends not to be used these days. It would not be more conservative to use a superelement, just more complicated.

If you have played with the model in line with the suggestions in Section 6.6 and you are still having problems, you should send the model, output and run files to EDI, the software people and see if they can help. I have found them very quick to respond.

You can do this if you have been keeping up with the software maintenance fees!

Hope this has helped.

 

[xpert]

The Superelement (6 x 6 matrix) is used when performing dynamic applications (vibration, fatigue, eismic etc).. it is the recommended method to be used for such analyses.