Strength of Bell‐and‐Spigot Joints

Although bell‐and‐spigot joints have been used successfully for many years in the construction of large‐diameter water‐pipe mains, questions sometimes arise concerning the efficiency of the joints under axial (longitudinal) forces. In this paper, a simple general‐yielding approach is used to develop an equation that can be used to directly determine the strength of such joints. The calculated joint efficiency, which depends on the ratio of the joint eccentricity to the pipe‐wall thickness, ranges from 0.41 for a zero gap to 0.24 for a gap equal to the pipe thickness. The equation is reasonable and conservative when compared to finite‐element results, to the ASME code, and to test results. Also, tests show that a single full‐thickness fillet weld can provide adequate strength. Such joints should be used wherever possible because they are much more economical than butt joints.