Problem:

Can we apply a 3-dimensional earthquake combination?

some believe that enveloping two planar earthquake combinations (X/Y and Y/Z) is still two dimensional. 

Answer:

This goes back to what is the requirement that is laid down by the standard which the user's  are following. For example, look at the following diagram from our online help for JSME 2008:

For JSME 2008, AutoPIPE provides the option to "apply all three directions at the same time", which can be checked or unchecked. You can see that for the dynamic seismic analysis it is considering R1, R2, and R3 (all three directions) to reach a D1xyz (dynamic in x, y, and z direction). However, you can also see that for static analysis, x combined with vertical y and z combined with vertical y. Now these requirements are derived from JSME 2008. Whatever project the user is working on, he should refer to what are the requirements laid down by the standard that they want to follow.

See Also

Bentley AutoPIPE

External Links

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

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