Protection of pipeline bridges against vibrations caused by a water hammer

Abstract

In pipeline systems, bridges are much more exposed to exceptional loadings and related failures than other elements of hydraulic plants. Water hammer, a phenomenon of abrupt change in fluid pressure caused by e.g. the sudden closing or opening of a valve, pump failure or a power cut, is an example of such loading. The reasons for this phenomenon and the possible failure it can cause are discussed in the article. An overview of the currently used protection methods against a water hammer and the possibilities to improve the construction of the devices that are used for such protection are shown. The effectiveness of three selected systems of protecting against a water hammer is discussed in detail. It is underlined that in the case of large-span pipeline bridges, especially suspension bridges, natural frequencies of the bridge can coincide with the frequency of the fluid pressure wave caused by a water hammer. This resonance can cause excitation of pipeline bridge vibrations. The possibilities of eliminating pipeline vibrations by applying vibration absorbers or flexible supports are pointed out. The importance of the need of detailed structural dynamic analysis and the determination of eigenfrequencies with their corresponding eigenforms is highlighted.