Section 2.5.8 for static analysis requirements is deemed to be satisfied in buildings that fulfill
the following two conditions: (a) The building period in the two main horizontal directions is
smaller than both 4TC (TC is defined in Sec 2.5.4.3) and 2 seconds. (b) There are no
irregularities in the structure.
In section 2.5.8, dynamic analysis should be performed for the following buildings: (a)
regular buildings with a height greater than 40 m in Zones 2, 3, and 4 and greater than 90 m
in Zone 1. (b) irregular structures with a height of more than 12 m in Zones 2, 3, and 4 and
more than 40 m in Zone 1.
For irregular buildings, smaller than 40 m in height in Zone 1, dynamic analysis, even though
not mandatory, is recommended.
Observation is here if we consider the floor height of a building is 3.0 m, and approximately a
20 story (for 2.0 S) regular building can be designed through static analysis in seismic zones 2,
3, and 4 as per section 2.5.6. But, as per section 2.5.8, dynamic analysis is essential for regular
buildings with heights greater than 40 m (13 story approx.) in Zones 2, 3, and 4. Which one
will be considerable?