Seismic Load Application as per IS 1893 - 2016

Seismic load is define as Horizontal/Vertical load due to ground motion cause of Earthquake. Load act at base/foundation of the structure called as base shear.

Seismic load depends on following:

• Weight of structure (W)
• Height and width of structure (H, D)
• Soil conditions (sa/g)
• Geographical area (Zone factor, Z)

To make earthquake resistant of structure we considered following,

• Importance of building (I)
• Response reduction factor (R)

By considering above factor, Indian code recommended formula to calculate horizontal seismic coefficient, Ah (cl: 6.4.2 IS 1893(Part 1): 2016)

Z is Seismic zone factor, which is depend on Territory of location. Indian Territory divided in four Seismic Zone and Zone factor as per Territory.

Seismic zone decide as per Earthquake prone area. Zone V means highest level of possibility of Seismicity whereas zone II associated with the lowest level of possibility of Seismicity.

Here are the zone factor for some of the well-known place in India.

Map of Seismic zone of INDIA:

I stand for importance factor, which is depends on type of building. 1.5 for highly important structure like school, hospitals and ancient building, 1.2 for business continuity structures and 1.0 for rest of structure. However structural engineer may choose higher.

R is response reduction factor. This value depend on type of structure given in IS 1893 (Part 1 to 5) 

Sa/g is average response acceleration coefficient which is depends on time period of structure and on type of soil. This is given in cl 6.4.2, IS 1893 – 2016.