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I am making manual load combination and I got struck in calculating Mapped spectral response acceleration Ss in order to calculate vertical component of earthquake Ev=0.2SdsD we have to calculate Sds which is equal to Sds=2/3Sms . and Sms=FaSs now according to section 11.4.1 of ASCE 7-05 it says in order to calculate Ss see figure 22-1 through 22-14 but these figures are maps and they are for US so how to calculte this parameter or whats the alternative for this problem to calculate vertical component of earthquake i am also attaching a picture of load comtination from ASCE 7-05

when we have raft foundation, is it necessary to draw it as we draw slab or just select all the joints at base level and turning them to fixed support will generate the effect of raft in analysis?

Increasing iterations does extra runs. Here is a tip regarding general P-Delta thing. Turn off auto line constraints and run your model. Choose either auto line constraint or P-Delta, not both for same run. It would solve the problem. If not, redo meshing to a regular pattern.

im still waiting for some to ask about over-strength factor..omega in seismic combinations..lets see when our curious young minds...raise this question...(as i said..im waiting for you )

1) goto File>Print Summary and ETABS will report you V = 0.05W something like this....means base shear V = 5% of W where W = effective seismic weight which is equal to the weight you put in mass source in etabs to check W ...after analysis...goto Display>Show Tables...Select all load cases you put in mass source and show Story Shears in tables> goto last story of model....you will see top and bottom of each story just add all load cases P (axial load) at the bottom most story (bottom)...this is equal to your effective seismic weight you put in mass source dialogue box note it down..lets say 1000 kip now similarly show tables and see EQx and EQy in tables at the bottom most story..both values should be equal if your time period and R are same in both load cases..this is your total base shear in x and y...you can see this value from the graph by Display>Show Story Response Plots.. lets say 100 kip So it means your V = 100 kips, W = 1000 kip which means your base shear = 10% of your effective building seismic weight 2) study UBC chapter on seismic design or IBC or ASCE ...you will find what is R...R is response modficication factor of building system...... values of displacements or drifts in ETABS are elastic....but earthquake design goes into in-elastic range...so to convert your elastic displacement value you should first convert it into in-elastic values before checking drifts...(this applies only for seismic design...as wind displacements remain in elastic region) in ASCE or IBC this 0.7R is equal to Cd/I where Cd is amplification factor for drifts in these codes..and I is the importance category... UBC is obselete now....start studying IBC 2006 or 2010...or if possible 2012...you are young generation...follow the latest codes..with background of old codes..I will upload here the 2012 code soon

i was also searching for manual load combination found it here

jazakALLAH and if i have load cases Dead, partition wall, flooring and live then i have to use 1.2 for dead, partn and flooring or only for dead ?

just goto HELP menu and open documentation for lateral analysis manual, there select your desire code...steps are given for each code in ETABS...and how ETABS handles code parameters...

Thats correct! You can define 4 or 6 cases based on your design theme.

sorry for drifts i replied in your other thread regarding p delta..please check that

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/

you need to make them fixed or pinned...and then export to SAFE and draw there the raft and do analysis in SAFE

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

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.

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

What do the local building authorities follow. If you are in Pakistan, you should go with UBC. Its pretty straight up. Make combos as per the article and use EQx and EQy at 5% default eccentricity. If you have an unsymmetrical building, you will end up with 4 earthquake cases. EQx + 5%y EQx - 5%y EQy + 5%x EQy - 5%x I cant open the link in the above post by Rana, so I cant comment on his post. IBC has a supplement, for different countries where they have given the values of SDs and SD1. I will look up at my documents. If I or Baz find it, we will post it.

For spectral acceleration values you have to consult values from local code in your country If you dont have a local code, you can get values from this site (USGS). ASCE values are based on USGS. https://geohazards.usgs.gov/secure/designmaps/ww/signup.php Just enter your email address and click on SIGN UP button, you must have java in ur pc to run online application. If the page does not load and you have chrome, then just click on SHIELD button in address bar just left to the "STAR" button to bookmark a page. After clicking click on "LOAD ANYWAY" button just enter the long and lat values of the place, To see the long and lat values you can use maps.google.com Alternatively, you can use UBC-97 as baz has mentioned, both are american codes. I would recommend you to read this interesting book about relationship between UBC and other american codes for seismic design. ICBO_UBC-UBC.pdf First the site classification in UBC are same as in IBC For Fa and Fv values see this image For Sds and Sd1 see this and for UBC seismic zones outside, see appendix of UBC code where some of the world cities are mentioned. For example, for Pakistan see the image below

never mind sir infact thanx alot sir may many and many people join in and get alot of benefits by sharing the knowledge as sharing knowledge increases the knowledge as you ppl are doing so alot of prayers and praises