Simplified Design Equations and Laboratory Tests for Pipe Joints

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Wang, Yu
Simplified Design Equations , Pipe Joints , Laboratory Tests
The joint may be considered a weak point along the pipe and can have a major impact on pipe performance. However, little research has been conducted in regard to joint design. To improve current structural design criteria, this thesis presents the findings and conclusions of experimental and computational studies of the effects of longitudinal bending on joints in rigid (reinforced concrete) and flexible (corrugated steel and thermoplastic) pipes. Solutions for expected shear force, longitudinal bending moment and rotation across the joint for rigid and flexible pipes are formulated for use in structural design of pipe joints. Exact algebraic solutions for rigid pipes are derived using the beam-on-elastic-spring approximation. The formulations for flexible pipes are developed assuming that the two pipes are very long, and that the response is not affected by either the location or characteristics of those other joints. The flexible pipe design equations are developed using various closed form solutions for beams on elastic foundations developed by Hetényi (1948). Parametric studies are then presented where the key factors controlling the behaviour are examined, and the comparisons to recent experimental measurements show that the joint rotation calculated using the equations and a value of soil stiffness proposed for use in design are generally reasonable and conservative compared with the laboratory tests. To measure the capacity of the joint to accommodate the demands, a pipe joint testing frame has been designed to facilitate joint characterization experiments. Shear tests and articulation (rotation) tests have been conducted using this testing frame to examine the shear force capacity, longitudinal bending moment capacity of moment-transfer joints, and rotational characteristics of joints. The shear test results show that the joints of PVC pipe and corrugated steel pipe have similar shear stiffness while the reinforced concrete pipe joint is significantly stiffer. The results of the articulation testing indicate that the rotational capacities of the three joint systems are similar in general. Design of rotational capacity of these joints is likely dominated by considerations of assembly in the field, rather than the rotational capacity that is needed once the pipes are installed.
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