Gentlemen,

The following is my opinion and is in part based upon informal conversations with outside resources, and information gained in discussions with knowledgeable qualified structural engineers.

The code changes which you comiserate about have been as a result of an increase in depth of knowledge and understanding of the mechanics involved in seismic design. Some of these newer sources have been the KOBE Japan earthquake, Turkeys problems etc.

These factors along with a desire of FEMA to produce less disaster prone U.S. buildings have stimulated to a certain extent some of these changes.

As for what remains the biggest threat to piping integrity? My opinion is that SAM or Seismic Anchor Motions are as big or a bigger threat to integrity! SAM effects are not covered per se under the UBC for piping but rather are dealt with in one of the piping code sections.

I suggest you look over some of the writings at www.fema.gov
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In summation loads have increase due to increased knowledge and concern.

To design for lateral loads and to not consider SAM when it is a factor will probably lead to piping failure during a major seismic event!

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Best Regards,

John C. Luf