RELATIVE MOVEMENTS FOR DESIGN OF COMMODITIES RUNNING BETWEEN TWO ADJACENT NUCLEAR SAFETY-RELATED STRUCTURES

摘要

In nuclear power plants a large number of commodities such as piping, HVAC, conduits and cable trays communicate between adjacent buildings. Such commodities supported by two adjacent buildings can be subjected to significant relative movements due to settlement and seismic event. For plants where adjacent structures are seismically separated and not founded on a common base mat, unless adequate care is taken, the design of such commodities maybe based on significantly underestimated relative movements. Relative movements due to building settlement may be significantly underestimated by neglecting the possible tilt of the structures. Relative movements due to seismic event maybe underestimated by considering only the calculated relative movements from seismic analysis of the two structures. Seismic analysis of the structures are performed either using fixed base analysis or soil-structure-interaction (SSI) analysis. In either case, the calculated movements from these seismic analyses do not account for any movement due to stability evaluations where passive soil pressure is considered to demonstrate stability against sliding and/or overturning. Furthermore, with certified designs for new generation of nuclear power plants, quite often the stability of the structure against overturning may utilize energy balance approach, which includes some tilting of the structure. The purpose of this paper is to discuss the above issues in depth and provide the readers suggestions and/or recommendations on how the design can appropriately account for such relative movements. In addition, since there is no current industry guidance on how to combine these relative movements, this paper presents a new formulation for combining applicable relative movements.