5 parameters to check an ETABS modeling

5 Parameter to Check in ETABS After Modeling and Analysis
5 Parameter to Check in ETABS After Modeling and Analysis

As a structural engineer, we also are asked to review the ETABS Model especially once you are the senior or head of the department or as a 3rd party checker. this is often to make sure that the planning shall meet all the relevant standards for safety, durability, and serviceability before submitting for authority approval.

This article aims to offer you the overall idea of the essential  Parameters checks and basic requirements that must consider in reviewing an ETABS model.

  1. Check for, Maximum Displacement in etabs

  • Go to Display tab menu
  • Select Story Response Plot
  • Select maximum Story displacement from display type
  • Select EQx from Load case and Check the maximum value
  • If it is with in Limit then its ok
  • Again select for EQy  and Check maximum Value if its in limit then ok.
  • Formula to check Max displacement=Building total height X 0.004 (from code)X1000 mm

  1. Check for, Maximum Drifts in etabs (IS 1893 part 1 ,peg28, Clause 7.11.1.1)

  • Go to Display tab menu
  • Select Story Response Plot
  • Select maximum Drift  from display type
  • Select EQx from Load case and Check the maximum value
  • If it is with in Limit then its ok
  • Again select for EQy  and Check maximum Value if its in limit then ok.
  • Formula to check Max drift=0.004 mm
Check for, Maximum Drift in Etabs
Check for, Maximum Drift in Etabs

Note: If  our Result Exceed maximum Limit Then Change (increase) Section Property of Beam  or Column then Check again using same method.

  1. Check for, Model Participating Mass Ratio in etabs

  • Go to Display tab menu
  • Click on Show Table
  • Select Analysis Result
  • Select Structure output and expand
  • Select Model information and expand
  • Select Model participating mass ratio
  • Click on Ok ,Now you have seen table now check :
  • We Need to Check : Time period, UX, UY,  SumUX (I.e. modal mass prt. Ratio) on 12th

 

Check for, Model Participating Mass Ratio
Check for, Model Participating Mass Ratio
  • Check for Sum UX (Modal Participating mass ratio)

-It should be always greater than 95% (ie. Value should be above 95) in 12th mode.

  • Check for Time period

-It should be Normal value that is if it is shown in 0.00X value its not Valid its abnormal.

  • Check for UX & UY (to avoid torsion)

We need to check Mode1 and Mode 2 Value in Criss-Cross, If any one group of them cross 40% Value in any one then its Ok.

Check for, Model Participating Mass Ratio
Check for, Model Participating Mass Ratio
  1. Check for, Center of Mass Rigidity XCR & YCR Value

  • Go to Display tab menu
  • Click on Show Table
  • Select Analysis Result
  • Select Structure Result
  • Check Center of Mass of Rigidity Under Other Output Items
  • OK
Check for, Center of Mass Rigidity XCR & YCR Value
Check for, Center of Mass Rigidity XCR & YCR Value

Here there is Not Calculated XCR & YCR Value initially in ETABS so we need to calculated it manually, For this:

  • First Unlock your Model
  • Go to analyze tab menu
  • Select set load case to run
  • Check for Calculate diaphragm Center of rigidity
  • Click on Run Now Bottom
  • Wait for 100% to finish.


  • Now again Run analysis model.
  • And Check Center of Mass of Rigidity (XCR & YCR) Under Other Output Items.
  • If those Values not Exceed 5% in each Story then it’s OK.
Check for, Center of Mass Rigidity XCR & YCR Value
Check for, Center of Mass Rigidity XCR & YCR Value
  1. Check for Torsional Irregularity

According to IS Standard the ratio of Max displacement and average displacement shouldbe less than 1.2.

$max < 1.2$avg                                                              ————–No irregularity

1.2$avg <= $max <= 1.4 $avg                                   ————–Irregularity

$max > 1.4 $avg                                                             —————— Extreme Irregularity

  • Go to Plan View and Select Top Story Plan
  • Go to Display Tab menu
  • Select Deformed Shape

-Check Torsion in EQx Direction

  • Select EQx load case
  • Click any Joints and Calculate  it  for EQx Direction ( ie. Select joints in Y –direction on etabs to get Value)

-(Avg Displacement = (11.275 +10.917)/2 = 11.096 mm =$avg

where, Max . Displace ment $max = 11.275 mm )

-Check, 11.275/11.096 = 1.016 <1.2 ———–( the model is not irregular in EQx)

$ max < 1.2 $ avg —– it is Safe

-Check in EQy Direction too.

  • Select EQy load case
  • Click any Joints and Calculate  it  for EQx Direction( ie. Y Select joints in X –direction on etabs to get Value)
Check for Torsional Irregularity in Etabs
Check for Torsional Irregularity in Etabs
Check for Torsional Irregularity in Etabs
Check for Torsional Irregularity in Etabs

 

NOTE : IF EACH CRITERIA ARE PASSED THEN START TO DESIGN

 

 

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