CSI changed the default background color in ETABS 13 to white. If this really bothers you and you feel a compulsion to change it back, just use the following easy-to-remember keyboard sequence:
Alt+O,C,D
What do you think: coincidence or CSI humor?
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I have been told that CSI has removed the .s2k export feature from this version. Is this true, and is there an alternative?
Tim – thanks for your comment. There is an inaccessible command hidden inside the program named “Export SAP2000 s2k Text File”, but it is not enabled. CSI support has confirmed that this option is not currently available but will be added to a future version. They further stated that much of the functionality of SAP is now in ETABS, so the export to SAP would be ‘seldom required’.
Update: CSI has shared with me a beta version of the ETABS to SAP translator. Leave a comment here if you’d like to try it.
Yes, I’m definitely interested.
I just posted a link to the ETABS-SAP translator.
Hello there,
Sorry for commenting here though my question is not related to this particular post, but I couldn’t find a way to contact you, Dan.
My question is related to Weights in ETABS. When I first learned ETABS 9.7.4 in college, we’ve been taught that the first check we need to do after the analysis is the difference between Weight Used and Weight Real. Weight used is the used weight by ETABS to calculate the Base Shear due to Static Earthquake load, whereas the Weight real is the total base reactions due to Dead (self-weight) and Super Dead loads (knowing that the mass source definition is self weight and super dead loads). The instructor told us that the difference should be less than 5% and I’ve noted that Wused is always less than Wreal. If the difference was more than 5%, we should modify the multiplication factor of the Super Dead in the mass definition to make the Wused equals to Wreal.
My question is why is there a difference in Wused and Wreal? And who set the 5% limit? I’ve searched a lot and couldn’t find it. And reading your “About” section encouraged me to post this question here.
Thanks in advance.
Mahmoud,
Thanks for your question. The difference between what you’ve named “Wused” and “Wreal” comes from two sources. The first and more significant difference is that ETABS ignores the seismic mass/weight of the bottom half of vertical elements (walls, columns, and braces) on the lowest level. If you have a significant number of walls, this difference alone can account for more than 5%, particularly for a short structure. Note that this assumption is based on common engineering practice, and thus the seismic mass often should be less than the dead load reactions.
The second difference comes from how ETABS calculates self-weight at member overlaps. How exactly they do this is something of a black box, but in some cases intersecting volumes of members are not counted twice. In all but rare cases, the resulting differences should be less than 5% and are most likely negligible.
As to the origin of the 5%, this probably came from your professor. I have never encountered this. It is, however, a reasonable threshold, keeping in mind the reasons for any observed differences.
All the best,
Dan
Thank you so much for replying 😀 You helped where others failed 🙂
Very interestring. Can someone please tell me how I perform this check? I mean, how do I find the used weight by ETABS to calculate the Base Shear due to Static Earthquake load. And how do I have a sum up of the total base reactions due to Dead (self-weight) and Super Dead loads.
Again, what is Super Dead load? Does it come up from the mass source definition i.e. 1.00Dead + 0,30Live?
Finally, I am interested myself in a Etabs to Sap2000 translator.
Thanks in advance
Taking your questions one by one: the weight used by ETABS for seismic loads can be found in the printed input tables (I usually save these to a text file and then open the text file). Base reactions can be found in the “Support Reactions” table – also see my post about the “Recovered Loads” spreadsheet. “Super Dead” load is shorthand for “Superimposed Dead” load and typically refers to all dead load that is not part of the structure itself (e.g. floor finishes, cladding, MEP, etc.).
See my recent post for the ETABS-SAP translator.
I dont know what I am doing wrong but I cant have the Responce spectrum base Reaction table (as seen at your spreadsheet at the instructions tab) at my 2013 Etabs. It’s not there although I have RS load case. Have been searching throughout the whole “Choose tables” tree and cant find anything. Any help would be much appreciated!
Tympos – You’re not doing anything wrong. ETABS 2013 does not have a separate Response Spectrum Base Reactions table. The RS base reactions are now included in the same Base Reactions table, which is a simpler approach.
how amplify eccentricity factor if my strucutre fail in torsional irregularity
Adjust the eccentricity ratio (“Ecc. Ratio”) in the earthquake static load case or the dynamic load case. Use the code provisions to determine the proper amplification. In ASCE 7-05, the amplification factor is between 1.0 and 3.0.
Dan
Not correcting you, Dan, but I guess you meant to adjust the Override Diaphragm Ecc. as shown here http://docs.csiamerica.com/help-files/sap2000/Menus/Define/Load_Pattern/Override_Diaphragm_Eccentricities_Form.htm
Mahmoud – I believe both methods work. Your suggestion would be best if you need to adjust eccentricity independently at each floor. Whether you need to do that would depend on the requirements of the governing building code.
That’s right. In my country we use UBC 97 as a building code, and we only adjust the diaphragms that have Delta max over Delta avg is greater than 1.2
S.K. Ghosh’s office has a very helpful blog post on this topic: http://skghoshassociates.com/SKGAblog/viewpost.php?id=5