Influence of Earthquake according to 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 | - | ||
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.