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Earthquake_Chinese_Standards_JTJ_004_89

Only horizontal seismic force is considered according to JTJ 004-89.

Seismic force on structure

Seismic force acting on structure is provided by (Art. 3.1.5):

where:

Eihw

-

seismic force acting at the center of gravity of the wall above the ith cross section [kN/m]

Kh

-

coefficient of horizontal seismic acceleration

Giw

-

weight of the structure above the ith cross section [kN/m]

Cz

-

comprehensive influence factor, usually it's 0.25

Ci

-

importance coefficient for seismic design

ψiw

-

distribution coefficient of horizontal earthquake along the wall

Recommended value of distribution coefficient ψiw (Tbl. 3.1.5):

Wall Height [m]

Security level

Calculation diagram for ψiw

Highway, A class and B class motorway

C class and D class motorway

H ≤ 12

ψiw = 1

ψiw = 1

H > 12

ψiw = 1

ψiw isn't considered when H ≤ 12 m which means parameter a and b don't work when H ≤ 12 m. a is the top value of the distribution map and b is the bottom value of the distribution map.

Seismic earth pressure

When computing seismic earth pressure, Coulomb theory is used and unite weight of soil γ, internal friction angle of soil φ and angle of friction structure-soil δ is replaced by γ / cos θ, sdasdasd φ - θ, δ + θ, where θ is seismic angle (Art. 3.1.6).

Seismic angel θ is determined by different option of seismic fortification intensity.

Water influence

Water influence according to Chinese standard is a little different from the water influence according to Mononobe-Okabe or Arrango theory by reducing the water influence using comprehensive influence factor Cz.

Seismic bearing capacity of subsoil

Seismic bearing capacity of subsoil is provided by (Art. 2.2.1):

where:

faE

-

seismic bearing capacity of subsoil

ξa

-

adjusting coefficient for seismic bearing capacity

fa

-

characteristic value of bearing capacity which has been modified by the geometry of foundation

The above formula is as same as Art. 4.2.3 in GB 50011-2010 (Code for seismic design of buildings). Suggested values of ξa by different standards can be found here.

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