Seismic analysis of a district heating pipeline

Abstract

The effect of seismic loading is not contemplated in any of the current design standards of District Heating and Cooling (DHC) networks, since this technology has been originally adopted in northern Europe, characterized by low earthquake vulnerability. Nevertheless, an increasing number of countries, including those in seismic areas like Italy, Turkey, China, Japan, and Chile are using DHC solutions due to the higher energy efficiency, compared to individual heating systems. Seismic regions are one of the most hostile environments for buried pipelines due to the effects of Transient Ground Deformation (TGD) caused by seismic wave propagation, and Permanent Ground Deformation (PGD), like faulting, landsliding, lateral spreading and buoyancy due to liquefaction. Most of research publications on the seismic analysis and design of buried steel pipelines have been motivated by the need of safeguarding the integrity of hydrocarbon pipelines, and there are no actual studies on the seismic vulnerability of DHC pipelines. This highlights the need to carefully evaluate the seismic performance of DHC pipelines, considering their typical composite cross-section and soil-pipe interaction under service loading. The present paper analyses the effect of diverse earthquake hazards on an operating District Heating (DH) pipe bend, usually susceptible to stress concentrations due to the greater flexibility, as well as the ability to accommodate thermal expansions, and absorb other externally-induced loading. The response of the operating DH pipeline subjected to different seismic loading is evaluated taking into account the geometric and mechanical properties of the system, including the soil-pipeline interaction. In conclusion, the obtained results give a better understanding on the seismic behavior of DH pipelines, highlighting important research ground for assessing their earthquake performance in operating conditions.