Seismic Response Characteristics of Buried Segment Pipeline with Typical Cross-connections

The joint type and pipeline cross connection of buried pipelines have a significant impact on the seismic response of pipeline structures. As the seismic deformation and stress of pipeline cross is determined by the structure types of branch pipelines, a finite element model of straight branch pipelines was firstly established to investigate the joint displacement, joint axial force, pipe-soil relative displacement, and pipe body stress of ductile iron pipelines (DIP) with flexible push-on rubber joints and cast iron pipelines (CIP) with rigid joint under seismic wave propagation. Then, the seismic response of pipeline connections using cross-shaped, T-shaped, L-shaped, and double-T-shaped cross connections were analyzed, where the pipe cross was connected to branch pipelines using push-on or flange joint. Furthermore, the effects of joint types on the seismic response of pipeline cross connections are evaluated. The results show that for the straight pipelines with different types of joints, the peak joint displacement of DIP with flexible joint is larger than that of CIP with rigid joint. When the pipe cross was connected with push-on joint, the peak joint displacement of the pipeline with double-T-shaped cross is slightly smaller than that of the pipelines with cross-shaped and T-shaped connections. When the pipe cross was connected using flange joints, the DIP with flexible joints adjacent to the flange joints exhibits a larger joint displacement and is prone to tensile failure, while the CIP with rigid joint adjacent to the flange joint experiences greater axial compressive force and is prone to compressive failure. At the cross of double-T-shaped pipelines, the response of the push-on joint adjacent to the flange joint is significantly larger than that of cross-shaped and T-shaped connections.