DESIGN SPECIFICATIONS FOR HIGHWAY BRIDGES - IISEE

6.4.3 Design Horizontal Seismic Coefficient
(1) Design horizontal seismic coefficient for Level 2 Earthquake Ground Motion shall be
calculated according to the following:
1) Design horizontal seismic coefficient for Level 2 Earthquake Ground Motion
(Type I)
Design horizontal seismic coefficient for Level 2 Earthquake Ground Motion (Type
I) shall be calculated by Equation (6.4.1). When the product of the standard value of
the design horizontal seismic coefficient (khc0) and the modification factor for zones
(cz) is less than 0.3, design horizontal seismic coefficient shall be obtained by
multiplying the force reduction factor (cs) by 0.3. In addition, when the design
horizontal seismic coefficient is less than 0.4 times the modification factor for zones
(cz), the design horizontal seismic coefficient shall be equal to 0.4 times cz.
k hc = c S c z k hc0 …………………………………………………………..(6.4.1)
where
k hc : Design horizontal seismic coefficient for Level 2 Earthquake Ground Motion
(Type I) (rounded to two decimals)
k hc0 : Standard value of the design horizontal seismic coefficient for Level 2
Earthquake Ground Motion (Type I), according to Table 6.4.1
c S : Force reduction factor specified in Section 6.4.4.
c z : Modification factor for zones specified in Section 4.4
In assessing liquefaction potential of a sandy soil layer in the seismic performance
verification for Level 2 Earthquake Ground Motion (Type I), the design horizontal
seismic coefficient at the ground level calculated by Equation (6.4.2) shall be used.
The design horizontal seismic coefficient used for calculation of inertia force caused
by the soil weight and the seismic earth pressure shall be obtained with reference to
Section 13.2.
k hg = c z k hg0 …………………………………….………………………….... (6.4.2)
where
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