A new approach to Stress Concentration Factors for tubular joint design
The fatigue design of tubular joints increasingly uses a single S-N curve based on the measured 'hot spot' stress range. Statistical analysis of the measured life delivers a corresponding design fatigue life with appropriately low probability of in-service failure. If a rigorous approach to probabilities is followed it is apparent that design should also address the reliability of predicting the 'hot spot' stress range for a given load and joint type. Finite element and acrylic model studies and many of the parametric formulae lack realism of the weld detail and cannot adequately cover the effects of weld profile variability and tubular tolerances. This paper presents the previously unpublished results of tests to determine Stress Concentration Factors for axial, in-plane and out-of-plane moment loading on over 30 steel tubular joints of realistic size and construction. It is apparent from the steel model tests that there is scatter in measured Stress Concentration Factors for nominally identical joints. These results are combined with the existing database of comparable tests and used to develop the concept of a design SCF defined in this paper. A detailed justification of the design formulae for SCFs is given. This new approach to SCFs incorporates the inherent variability of tubular joints in a manner which is consistent with the rigorous approach now being adopted for fatigue life assessment. This leads to a clearer understanding of the apparent scatter in observed performance of tubular joints and reduces the risk of gross underestimation of SCFs which is possible using current techniques.
- Research Organization:
- Wimpey Offshore Engineers and Constructors Ltd.
- OSTI ID:
- 6452039
- Report Number(s):
- CONF-8405208-
- Journal Information:
- Proc., Annu. Offshore Technol. Conf.; (United States), Journal Name: Proc., Annu. Offshore Technol. Conf.; (United States) Vol. 3; ISSN OSTCB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360103 -- Metals & Alloys-- Mechanical Properties
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420206 -- Engineering-- Mining & Drilling Equipment & Facilities-- (1980-1989)
423000* -- Engineering-- Marine Engineering-- (1980-)
ALLOYS
CONSTRUCTION
DESIGN
DIAGRAMS
FATIGUE
FORECASTING
HOT SPOTS
IRON ALLOYS
IRON BASE ALLOYS
JOINTS
LOADING
MATERIALS HANDLING
MATERIALS TESTING
MATHEMATICS
MECHANICAL PROPERTIES
PERFORMANCE
PROBABILITY
RELIABILITY
S-N DIAGRAM
SERVICE LIFE
SIZE
STATISTICS
STEELS
STRESS INTENSITY FACTORS
TESTING
WELDED JOINTS