It can be inaccurate. Approximating dynamic events in a static analysis provides results "close" to the actual behavior only if the response of the system is dominated by a single mode of vibration. If you have mulitple modes contributing the static analysis becomes more inaccurate.



I can't answer that one - it really depends on the system and how it responds to the load.



The CAESAR II Dynamic Seismic Analysis is performed implementing the Response Spectrum Method. Check out the NUREG9 example job that ships with the software.