Leaderboard

You should select "Include special seismic" and in DL multiplier use the value of 0.2SDs. When you do that, your automatic load combos would always be correct and will have the vertical component of earthquake added. Do it, and check manually. Code requires you to apply earthquake loads at a eccentricity of plus minus 5%. When you define a load case, say Eqx it is defined in X direction. you need to select EQX + ECCEN Y(5%y) instead of EQx only(see above image). Similarly, define a new load case in EQX -ECCENY(5%y) to satisfy that code provision. Repeat same for other direction. Its great to see more female engineers joining the forum. Zoya do tell your other friends too who are in the same field and lets make this place more active and more productive.

if you are designing a concrete structure only..the trick is to use steel or vice versa.. go to option>steel frame design preferences>and select ASD in design code..then goto define>add auto load combos and tick on convert to editable this way you can make auto generated service load combinations you need service combos not only for foundations but also to check wind drift and other serviceability criteria you need these service combos usually in SAFE not in ETABS but its preferrable to add service combos in ETABS too if you are used to check deflections and drifts in ETABS...its upto u use just 4 load cases for earthquake not 6 if you are designing for lahore (seismic) vertical component will be less than 0.2 depending upon the value of Sds...you can ignore it then in ETABS this factor is 0.2 by default in special seismic load combinations dialogue box...this is called DL multiplier in ETABS..by default its 0.2...you have to change it manually..remmeber it for wind...remember this that for drift you need to multiply W by 0.7 to convert it into service level wind for drift (10 year return period..) if you are not using UBC... please search in the forum for these topics..some of these things are already covered..before... good luck

there are many reasons for these errors..you should not let it happen for example extrude your model and check if your geometry is okay...some times...1000m is put instead of 1000mm in section properties making very stiff elements with flexible check if out of plane modifiers are applied to membrane check if base is properly restrained...some times like in springs..vertical restraint is provided but not horizontal if your struc is 2d make sure to analyze it in 2d not in 3d in analyze>analysis options menu check if vertical elements are not accidently deleted in mid stories distrubing the load path check if very thin shells are modelled... and so on

in p-delta parameters what is the use of maximum iterations? and what are the combination and their scale factors we should put there?

Please refere to CSI wikki and search for p-delta they recommend you 1.2D+0.5L reasons is that it covers all the load combinations in ACI chapter 9...(conservatively) for lateral analaysis.. for P (big P) delta..you need to include all gravity loads that are with lateral load combinations.. as lateral loads will sway your frame...and will create some displacement lets say in column...then the column will experience magnified moments because of the P (axial dead loads on colum) so this P multiplied by delta ...create moment M = P.e start with 2 or 3 ietration then aftera analsyis...goto last analysis run log and check if p delta converged or not...if not then increase the number of iterations... please have a look at this manual in this thread...it will clear some of your doubts http://www.sepakistan.com/topic/28-etabs-model-checking-tips-tricks/ for drifts...see this topic on my website or search in this forum: http://www.ranawaseem.com/

Take a look at this link https://wiki.csiberkeley.com/display/etabs/Lost+digit+of+accuracy . One thing that you do is to zoom into that point, reported by ETABS, and see if all the members are connected to that point.

@umar Makhzumi u said that (Make sure, have your loads at default eccentricity because that can effect your results a lot) i did not got this point? can u define it more??

Just use the DL multiplier(0.2SDS) here and your auto load combos would be okay! Do a manual check.. combos should match up

To go by the book, you should consider 0.55CaI(0.2SDs) for 1.32 and 0.9D Cases. If someone is neglecting the clause for 1.32D and they can justify that it is reasonable and effect is least, than you can accept that. But considering in Pakistan, all design is done using softwares, so I don't see any point in missing that unless you are doing stuff manually and want to save calculation time. Make sure, have your loads at default eccentricity because that can effect your results a lot.

The reason that 0.55CaI or vertical component of earthquake is neglected for 1.32D is that it effects are more pronounced with 0.9D load case.This is explicitly stated in ASCE. So you should consider that in 0.9D Load case. I honestly dont remember exactly, but It was like this. Its been years since I last used UBC or ASCE.

Here are the SDS and SD1 Values for Islamabad, Karachi, Lahore & Peshaware.

your model looks okay, but following are some of my concerns apply torsion modifier for beams = 0.35 slab modifier are not applied...make them m11=m12=m22=0.25, this will increase your sawy too story8 slab load above grid 6 is not applied story2 and story 8 diaphgram extent misses some external points...look at that make sure your load combination are okay ​wall meshing is missing in your model....mesh them your base-shear is equal to about 5% of seismic weight which seems okay with R=5.5 and UBC 2B seismic zone You dont have to worry about the magnitude as far as you satisify the seismic drift limits of UBC which are 0.025 and 0.020 times story height...based on time period of your building....remember to convert your elastic displacement values to inelastic displacement by mulitplying it to 0.7xR also check the building separation gap, if necessary again, make sure your load combinations are okay! one last thing: incease the column cross section, for 8 storey building in 2B zone, they look smaller...increase the size...to reduce your reinforcement from 3%...make them to 2 or 1.5%.... rest your model is okay apart from above points of concern good luck..keep us updated

Where will this construction take place? US has reported these values for different cities of the world for the construction of their facilities. I will try to find the document; I once consulted it . Or, you can change code; use UBC 97.