Design of steel energy absorbing restrainers and their incorporation into nuclear power plants for enhanced safety. Volume 2. Development of analyses for reactor system piping

The results of an investigation into the desirability of using solid-state nonlinear hysteretic energy absorbing restrainers as the supporting elements for nuclear power plant piping systems are presented. These results have been generated for three cases representing simple piping systems, namely, (1) linear pipes with linear restrainers, (2) linear pipes with elasto-perfectly plastic restrainers, and (3) linear pipes with Ramberg-Osgood type restrainers. Realistic seismic response produced at typical support points within a power plant main structure is used as the input excitation to the support restrainers. Dynamic time-histories of response have been determined for each case over prescribed ranges of the critical parameters and the significant results have been correlated. The results of the investigation show that nonlinear energy absorbing restrainers can be very effective in reducing seismic forces in piping systems, without excessive yielding, provided they are properly designed. Restrainers of the Ramberg-Osgood type have been found to be very effective when the characteristic parameters are properly controlled. Based on the results of the overall investigation, it is concluded that nonlinear hysteretic energy absorbing restrainers can improve the seismic performance of nuclear power plant piping systems resulting in cost savings and enhanced safety.