Unlike in SAFE where you can import/export Excel files or copy from Excel and paste to SAFE, ETABS doesn’t have that feature – yet (maybe they will eventually incorporate this on their succeeding upgrades or maybe they won’t.) This would have been very handy especially if you start from scratch to define a hundred or so load combinations. But until then, you need to do it manually by defining it one by one in the GUI.
It’s not a pleasant task but it is necessary. Just imagine creating service wind load combinations to check the wind drift. In ASCE, there are 4 cases to consider including the possible combinations of the eccentricity (ETABS generates 12 wind load cases). Add to that the SLS (service limit state) gravity and seismic load combinations to complete the piling loads or to check and ensure that the allowable soil bearing pressure is not exceeded. And of course the ultimate limit state or ULS load combinations such as ultimate wind load combinations to design the columns and wall reinforcement, and the ultimate seismic load combinations to assess the seismic drift and to complete the necessary strength level combos.
But the list doesn’t end there.
If you have hydrostatic uplift, retained soil, Mononobe-Okabe loads and envelopes, that’s quite a lot to accomplish. And as I said, if you’re starting from scratch, it’s quite a handful. But if you don’t have the luxury of time to build the new model on an old ETABS template where your load combinations are already defined, don’t fret my friend because this is your lucky day. Like Staad’s text editor, you can use the text file $et of ETABS.
First, you have to rename the load patterns and load cases (including the necessary load factors and other parameters) with the same load patterns and load cases you are copying from. Study the syntax (how ETABS defines load patterns, cases, combos, and combos within a combo, see sample above), generate the syntax considering all load combinations in Excel, paste in the $et file, save, and import the said text file and that’s it! A half day’s work done in less than half an hour.
The same can also be done for frame column definitions. In one of our projects, the client required that we input the rebars reflected in the column schedule to the model so that when a third party reviewer will run the design, he can see in an instant if the columns pass by just looking at the PMM ratio or the demand/capacity ratio. In order to shorten the time required for this, our design manager defined the column tags, sections, and reinforcements. After which it’s just copy, paste, and import and it’s done.