Abstract: Buried pipelines,especially the water supply pipeline network,are often damaged at mechanical joints under severe ground shakings were caused by a strong earthquake.Seismic design of buried pipelines with flexible joints includes two parts: checking the strength of segment of pipelines and the deformation of joints.A simplified method considering the elasto-plasticity of joints was presented to analyze buried segmental pipelines under the action of seismic motions.The segmental pipeline was simulated as an equivalent uniform pipe having the same force-deformation relation with the original pipe-joint system.The deformation of the equivalent uniform pipe under the action of seismic wave was derived by means of seismic deformation method.Based on the obtained deformation,the accurate axial force of segmental pipelines and deformation of joints could be calculated by analyzing the force-deformation relation of each segment-joint unit.The proposed formulas were applicable for the PVC and cast-iron pipelines.Some numerical examples were investigated by comparing the results of the simplified method and those of FEM.The results of the simplified method agreed well with those of the FEM and this method could be used more simply and conveniently than the FEM in the seismic design of buried segmental pipeline system.