Abstract
Simple support structures such as U-bolts and clamps are used for the low-seismic-class piping designed using the constant pitch span method. Recently, the safety of the piping is required during the earthquake, and the demand for safety in nuclear power plants has increased. As a result, the high seismic resistance has also been required for the low-seismic-class piping. In the response analysis, the support structure constrains the displacement in two translational directions, but not the axial displacement of the pipe. Depending on the routing of the piping, a large axial response displacement may occur, and the structural integrity of the piping and the support structure may not be ensured. Therefore, measures have been taken to add or reinforce support structures. In practice, pipes are subjected to the axial friction resistance by the support structure, which reduces the response displacement. A static element test was conducted to understand this axial resistance. In this test, the friction resistance force was measured with no tightening force. Specimens were G28 (about 3 kg) and G54 (about 6.5 kg) pipe elements. The resistance force about 3.5 to 7 N for G28 and about 7 to 15 N for G54, and the friction coefficient about 0.18 were observed. By taking this into consideration, it is expected that the response displacement during the earthquake will decrease. The development of a rational seismic evaluation method considering the frictional resistance in the axial direction will be continued.
