Modelling of 25 storey building with the specified properties using ETABS

Answer to Exercise:1:

The Time period of the structure is in the given range in the X and Y directions.

Answer to Exercise:3:

The displacement along the X-direction is translational from the image below and not rotational

The displacement of the building in the second mode is also translational to the time period Ty=4.222 seconds as shown below.

a)The mass participation ratio is up to more than 80% for the first three modes in both directions

b)The Time periods in the X and Y directions are 4.416 and 4.222 and their difference is less than 10%, i.e, 4.3%. This condition does not validate with respect to the target time periods, which have a difference of 4.2%.To get the time period difference between the first two modes should increase the number of bays in the Y direction of the building, which is not per the given layout. However, the building is in zone III, were points a) and b) are not to be applied.

Answer to Exercise:2:

The image below represents the displacement of the center of mass which is in a positive and negative direction representing the displacement along the same vertical line from story 5 for torsional mode having a time period T=3.312 seconds which is less than the first two fundamental time periods.

Answer to Exercise:4:

Given below is the drift for the Load combination DL+WL+LL+EQX+0.3EQY, which has a maximum drift of less than 0.004 i.e.,<0.004

Given below is the drift for the Load combination DL+WL+LL+EQY+0.3EQX, which has a maximum drift of less than 0.004 i.e.,<0.004