base shear

1) go to File>Print Summary and ETABS will report you V = 0.05W something like this....means base shear V = 5% of Wwhere W = effective seismic weight which is equal to the weight you put in mass source in etabsto check W ...after analysis...go to Display>Show Tables...Select all load cases you put in mass source and show Story Shearsin tables> go to last story of model....you will see top and bottom of each storyjust 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 boxnote it down..lets say 1000 kipnow 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 kipSo it means your V = 100 kips, W = 1000 kipwhich means your base shear = 10% of your effective building seismic weight2) study UBC chapter on seismic design or IBC or ASCE ...you will find what is R...R is response modification 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is equal to Cd/I where Cd is amplification factor for drifts in these codes..and I is the importance category...UBC is obsolete now....start studying IBC 2006 or 2010...or if possible 2012...you are young generation...follow the latest codes..with background of old codes..I will upload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