Damage criterion and safety assessment approach to tubular joints

Based on the Continuum Damage Mechanics (CDM), a damage criterion is propos ed to predict the macrocrack initiation for tubular joints. The guidance on prediction to ultimate load carrying capacity of flawed tubular joints is provided by means of the modified Central Electricity Generating Board (CEG B) Failure Assessment Diagram (FAD). Non-linear FE analyses were carried ou t on uncracked and cracked T, K and KK tubular joints. Triaxial stress dist ributions and equivalent plastic strains near weld toes in the chord around the brace were numerically obtained for uncracked tubular joints. The crac k driving force, J-integral, and ultimate collapse loads of cracked tubular joints subjected to axial brace loading were evaluated by FE analyses. Loa d-displacement curves and ultimate strengths for uncracked and cracked T, K and KK-joints were numerically determined. A uni-planar KK tubular joint s pecimen was tested under anti-symmetrical axial loads. During the test, the load-displacement curve and the ultimate strength were measured. Meanwhile . crack initiation and growth were observed until complete failure. FE and test results show that the damage criterion gives good prediction for macro crack initiation in tubular joints, and the modified CEGB approach is suita ble for the safety assessment to flawed tubular joints. (C) 1999 Elsevier S cience Ltd. All rights reserved.