The following summarizes CP&A's procedures for crane projects that require dynamic seismic design, sketches possible damper positions on a typical crane, and provides several linear time-history and non-linear time-history results for a typical container crane.

Design procedures

1)      Preliminary crane structure design

Gets the preliminary crane structure design using static Finite Element Analysis (FEA) method, or by other means.

2)      Linear Time History Analysis (LTHA)

This includes adding recorded and probability modified seismic motion records, running every specified seismic combination, checking member stresses based on ANSI/AISC 314-02 or user specifications for each specified level of earthquakes, and using R factor adjustments per FEMA 356 or other codes specified by User.

3)      Non-Linear Time-History Analysis (NLTHA)

If the LTHA generates an impractical or uneconomic result for the seismic records and combinations, provide an alternate solution by adding anti-seismic dampers to reduce the seismic load affects. This includes modeling the non-linear behavior, determining anti-seismic damper locations, sizes, and stroke lengths, and checking member stresses based on NLTHA runs.

Conclusion

Dynamic analysis, design, and detailing of complex structures requires significant experience, training and knowledge.  CP&A has gained significant understanding and experience with this type of analysis and design during the past 15 years.  CP&A was the lead seismic designer for the Boeing aircraft assembly building seismic upgrade using dampers and non-linear time-history analysis.  Boeing’s Everett assembly building is the world’s largest building by area.  Our seismic experience began back in 1992.  We worked with Dr. Edward L. Wilson, the professor who pioneered the first dynamic non-linear analysis algorithms using load-dependent Ritz vectors.  Since then, CP&A has continued to be a pioneer in this field and has designed and analyzed numerous structures using dynamic analysis methods.