Fatigue Analysis of Load-Carrying Fillet Welds

Abstract

The fatigue strength of load-carrying fillet welds is, in most codes of practice, performed neglecting the influence of bending in the weld throat section. However, some commonly applied structural details give rise to significant bending in the weld throat section. An example of such a detail is a doubler plate connection, which is often applied in connection with modifications of offshore structures. As a part of the present work, fatigue tests have been performed with test specimens fabricated by the current industry standard for welded offshore steel structures. The fatigue tests show that the degree of bending (DOB) has an influence on the fatigue lifetime. The fatigue lifetime decreases significantly when increasing the bending stress. In order to take into account the effect of the bending, a new fatigue stress definition applicable for fillet welds failing through the weld is presented. Using the test results, it is shown that the new definition of fatigue stress can be used for a wide range of DOB with a low standard deviation of the resulting SN curve.

Fatigue performance of tubular X-joints with PJP+ welds: I — Experimental study

“…Root cracking has become a critical concern in connections made from fillet welds [28,29]. The post-test sectioning of the X-joints reveals that root cracking does not occur in the specimens J1 and J1-F, which do not include the surface treatment to enhance the fatigue life against toe cracking.…”

“…However, the fatigue life enhancement enabled by the weld toe treatment may postpone the toe cracking and cause potential root failures as observed in some experimental studies [26]. In general, root cracking is not a common failure mode in well-controlled laboratory tests for tubular joints, but an often observed failure in load carrying cruciform type joints [27][28][29][30].…”

Evaluation of Weld Root Failure Using Battelle Structural Stress Method

“…4 [11][12][13][14][15][16][17]. The joint plate thicknesses and the weld leg lengths evaluated are 10-4^0 mm and [11][12][13][14][15][16][17] 4-11 mm, respectively. 4, cyclic tension loading was applied for all joint types; load-carrying cruciform joints [11][12][13][14][15][16][17], doubler plate joints [15], and tube joints [16].…”

“…As indicated in Fig. About 300 fatigue testing data collected from [11][12][13][14][15][16][17] were employed for this evaluation of weld root failure. The joint plate thicknesses and the weld leg lengths evaluated are 10-4^0 mm and [11][12][13][14][15][16][17] 4-11 mm, respectively.…”

Reliability-Based Design and Planning of Inspection and Monitoring of OffshoreWind Turbines

“…The Maximum-Likelihood Method (MLM) is used following the same general procedure as in e.g. Sørensen et al (2006) where uncertainty modelling of the fatigue strength capacity of the loadcarrying fillet welds is considered. The uncertainty modelling is important in order to determine the characteristic fatigue design curves as well as in order to perform the reliability analyses and eventually to calibrate/assess partial safety factors.…”