In order to export a 3D steel model from ETABS to Advance Steel, you need to do the following:
- in ETABS, go to File > Export and choose the option "Steel Detailing Neutral File ..." (which corresponds to the well-known SDNF file format)
- the generated file gets the .SDN file name extension => rename it to .SDNF file name extension
- in Advance Steel, click "Import SDNF" icon and select the renamed file
=> the 3D model is correctly imported into Advance Steel, and you can use e.g. the automatic connections from the AS "Connection vault" to connect beams together.