Estimations Of Stress Concentration Factor For Fatigue Design Of Welded Tubular Connections

The S-N approach with hot-spot stress range concept is a widely used method for the fatigue design of tubular connections in fixed offshore structures. In order to use this method, realistic values of stress concentration factors (SCFs) in the tubular connections are required. A number of alternative parametric equations are available for the calculations of SCFs. However, there is still a paucity of test data on realistically constructed and sized specimens for some basic joint types to validate these equations and to select the most suitable equations for use in design.

This paper presents results of a total of 45 elastic tests carried out on 15 realistically constructed and sized tubular joint specimens of either T, Y, X or K configuration. The tests concentrate on joints with high ? (brace to chord diameter) ratios. The SCFs of these specimens under either axial, in-plane bending and out-of-plane bending loads were estimated using strain gauges readings. Three different extrapolation techniques have been used to interpret the measured results. An assessment on the reliability of SCF parametric equations for fatigue design has been carried out in the light of the new test data.