Design Acceleration

[EricM9]

This is my first time to design a retaining wall. Im using Retain Pro software. One of the inputs is Design Acceleration, Kh under seismic loads. Can someone give me idea how to find the correct design acceleration? The geotechnical engr only supplied the following data:
UBC 1997
Soil Factor = 0.4
Soil Type = SD

Also, is there a limit on height of retaining wall where seismic is to be considered? Example, if the height is less than 4ft then you dont need to consider seismic.

Hope you guys can help me on this.

Thanks!

 

[MSEMan]

Calculate the Kh using Monabe-Okabe formula. See AASHTO. For walls and situations where a permanent horizontal deformation can be accepted without structural distress the formula is modified to the following:

Kh = 1.66(Am)(Am/d)^0.24 where d is the acceptable permanent horizontal deformation in mm and Am is the ground acceleration coefficient.

Hope this helps.