Repair records after the 1994 Northridge earthquake show that approximately 60% of critical trunk line damage in the Los Angeles water distribution network occurred as compressive buckling of welded slip joints. This paper summarizes the results of experimental and numerical studies to characterize the deformation and buckling behavior of welded slip joints that were both unreinforced and retrofitted with fiber-reinforced composites (FRCs). Laboratory tests of pipelines fabricated under field conditions show that 12-in. (300-mm) -diameter joint specimens retrofitted with FRCs achieved 27% higher compressive load capacity over unreinforced specimens. The FRC wrap restrained outward buckling and restored the axial capacity of the slip joint to that of a straight pipe section. Analytical models, validated with respect to the test results, show that the gain in compressive capacity can be over 100% for larger size joints with diameter-to-thickness ratios of 150-200.
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