NUMERICAL ANALYSIS OF PLASTIC LIMIT LOADS OF LOCALLY THINNED ELBOWS

Local wall-thinning, as a common defect on the surfaces ofpipelines, not only reduces the load-carrying capacities, but alsocauses serious failure accidents of pipelines. In this paper, a computationalmethod for plastic limit loads is adopted. The plastic collapse analysis ofdefective pipe elbows under internal pressure and bendingmoment is performed by the proposed algorithm. The defects considered here includepart-through spherical, ellipsoidal and rectangular slots. Based on a numberof numerical examples, the limit loads of pipe elbows are computed for arange of geometric parameters. The effects of axial, circumferential, smalland large area local wall-thinnings with different sizes on load-carryingcapacities of pipe elbows under internal pressure and in-plane bendingmoment are analyzed. Some typical failure modes corresponding to differentconfigurations of slots and loading forms are studied. The computationalresults can provide theoretical foundations for the safety assessment ofdefective pipe elbows.