Analysis of mechanical response of rigid pipe joint based on beam-spring model

Pipe joints are the most vulnerable components in rigid pipeline systems. To investigate the mechanical response characteristics of pipe joints under surface loading and soil pressure, this study derives analytical equations for the shear force and rotation angle at rigid pipe joints based on the beam-spring model. The analysis focuses on the effects of key parameters, including pipe diameter, pipe length, surface load magnitude and distribution length, and soil stiffness, on the joint response. The results indicate that, compared with the conventional two-beam model, the proposed four-beam model more comprehensively accounts for the interaction among multiple pipe segments, yielding results that better reflect the actual service state of buried pipelines. When the soil stiffness is set to the design value, the rotation angle at the middle joint of 600 mm and 1200 mm diameter pipes calculated by the four-beam model is reduced by up to 21.2% and 19.2%, respectively, compared with that obtained from the two-beam model. Under shallow burial conditions, the joint shear force induced by surface loading increases with pipe diameter, pipe length, and load magnitude, but decreases with increasing load distribution length. The shear force at the middle joint of the 600 mm and 1200 mm diameter pipes exhibits a local peak at a burial depth of 0.3 m, reaching 55.3 kN and 74.3 kN, respectively. As burial depth increases, the joint response gradually transitions from being dominated by surface loading to being governed by soil pressure.