You can convert the trajectory to gromacs format and try. I don't think there is any other possibility other than this available in yasara. However, you can contact Elmar for more details.

Thank you Nikhil for your replay. Could you please provide me Elmar's contact link?

well, gromacs trajectory type is .xtc or .trr. Instead of converting trajectory it would be better to run the simulation in gromacs. Otherwise, you may need to use some script (Mdanalysis may be helpful) to get the secondary structural changes with dssp. I would go with running simulation in GROMACS

I did convert .sec of YASARA to .xtc format. Could you please provide me loading script in GROMACS for DSSP analysis?

You can use gmx dssp command in gromacs to analysis the secondary structure.

gmx dssp command doesn't give result per-residue wise for YASARA trajectory because the topology is not accurate as gromacs . So, directly contact with yasara support for getting the script. Currently YASARA supports per residue wise secondary structure calculation. Look at http://www.yasara.org/mdreport/4mbs_report.html for more details. In this case you do need to upgrade your yasara.

There is another method, just install XSSP 3.0 and go for calculation.