Combination of the total vertical dead load and the reduced vertical
Basic seismic coefficient
This value shall be determined from Fig.1 for the seismic zones shown in
Fig.2 using the structural period and the types of subsoil.)
Importance factor (See table
Structure type factor (See table
types of subsoil
The types of subsoil are considered in selection of C — firm and soft. For
the purpose of this code a structure shall be considered as being on a soft
subsoil if it is located on soil deposits exceeding the following depths.
soils less deep than these limits the subsoil shall be considered as firm.
a cohesive soil with an average undrained shear strength not exceeding.
5kg per sq.cm. (50 kPa) : 6m
site where the overlying soils are either cohesive with an average
undrained shear strength not exceeding 1kg per sq.ca. (100 kPa) or a very
dense granular material : 9m
a cohesive soil with an average undrained shear
strength not exceeding 2kg per sq.cm. (200 kPa)
a very dense cemented granular soil : 20mn
provisions should apply regardless of whether there are piles extending to
a deeper hard layer.
shall be measured from the level at which the ground provides effective
lateral restraint to the building.