Stress Analysis Criteria for Piping. RCC-M 2002 Rules and Validation.

摘要

The 2002 addendum RCC-M code introduced a new rule for stress classification of seismic loads in piping systems stress analysis. It allows the application of a reduction factor on the elastically calculated seismic moment in order to quantify the primary part which shall be introduced in the stress limitation equations. In linear response spectrum analysis using widely broadened spectra, with an usual low damping ratio ξ,this reduction factor is equal to : τ =(ξ/10)~(1/2) . This reduction is valid for usual piping systems which havenot their main frequencies in the high frequency region of seismic spectra. It is a behavior coefficient, similar to those used in structural design codes, equivalent to the use of inelastic spectra.Equations in piping design codes for faulted loading conditions are compared and applied to piping test results. The application of the new rule with level D criteria gives allowable loads two times lower than allowable loads derived from piping tests. Available test results validate the new RCC-M 2002 criteria for seismic design of piping. Seismic stresses are only partly a primary loading. As this new rule provides margins in piping analysis still larger than two, the industrial practice remains consequently severe.