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( Criteria for Earthquake Resistant Design of structures )
Where,
| W | = | Seismic weight that is full dead load + Appropriate percentage of imposed load (see Table 1) |
| Ah | = | Design horizontal acceleration spectrum value |
Where,
| Z | = | Zone factor (see Table 2), |
| I | = | Importance factor (see Table 3), |
| R | = | Responce reduction factor as given in, I/R shall not be greater than 1.0 (see Table 4) |
 |
= | Average responce acceleration coefficient (see Fig. 1) for rock and soil site and based on fundamental natural periods and damping (see table-5) of the structures. These curves represent free field ground motion. |
Ta = 0.075 h 0.75 for R. C. Framed building
= 0.085 h 0.75 for Steel Framed building
where,
h is height of the building in m.
For others building may be estimated as below,
Ta = 0.09 /√(d)
Where,
d (in m) is base dimension of building at plinth level along the considered direction of the lateral forces.