The problem above is caused by link element. Change them into beam elements. And I found OSN v2.5.5 could recoginize the link element and import s2k file for SAP2000v16,but failed to write them into tcl files,which is not the case for v14.2.it seems that OSN cannot recognize the link elements in s2k file for v14.2.
And after eigen analysis, the periods and mode shapes exist significant error between SAP2000 and OSN. I am going to continue finding the reason for this problem.
