Issue 45

D. Yang et alii, Frattura ed Integrità Strutturale, 45 (2018) 45-52; DOI: 10.3221/IGF-ESIS.45.04 51 that in Condition 1. The results demonstrate that the brace-side and chord-side SCFs declined when the brace-side and chord-side weld sizes increased by the same amount. Fourth, WT5 and WT6 shared the same weld size at the brace-side, but WT5 had half the weld size of WT6 at the chord- size. In both conditions, the SCF decreased slightly with the increase of weld size at the chord-size, and increased at the brace-side. Fig. 9(c) describes the effect of fillet weld size on the SCF in Condition 1. The effect of fillet weld size in Condition 2 was similar to that in Condition 1. The effects can be explained as follows: With the growth in chord-side weld size, the angle between weld surface and brace wall expanded, adding to the slope of the transition area between the weld and the wall. R ECOMMENDED WELD SIZES hrough the simulation of six models, it is clear that the joint SCF is indeed affected by weld size. This section attempts to recommend rational weld sizes for engineering practice. The idea of Wingerde fails to ensure the safety of brace-side SCF for full penetration butt weld, while the idea of Zheng Hongzhi complicates the SCF calculation with the consideration of brace-side minimize weld size. Considering the relevant specifications, the author recommended the following weld sizes which are easy to compute and implement. First, the chord-side SCF of full or partial penetration weld joints increased significantly with the decrease of chord-side weld size, but insensitive to the variations in brace-side weld size. In actual projects, the weld size should be minimized at chord-side and set to a common size at brace-side (Fig. 10(a)). The chord-side SCF calculated of our finite-element model is the upper limit of the actual chord-side joint SCF. Thus, it is safe for engineering application. Second, the brace-side SCF of full or partial penetration weld joints was almost the same as that at chord-side, because the joint SCF increased with the decrease of weld size. Thus, both brace-side and chord-side weld sizes were 1.2t1 (Fig. 10(b)). The brace-side SCF calculated of our finite-element model is the upper limit of the actual brace-side joint SCF. Thus, it is safe for engineering application. Third, the fillet weld size was set to 1.2t1 for simplicity and applicability, because the SCF of fillet weld joints grew with the decrease of weld size. The size was the same as that for computing the brace-side SCF of joints connected by full or partial penetration weld (Fig. 10 (c)). The SCF calculated from our finite-element model is the upper limit of the actual fillet weld joint SCF. Thus, it is safe for engineering application. (a) (b) Figure 10: Recommended weld sizes in finite-element calculation. C ONCLUSIONS inite-element analysis reveals that the weld size directly affected the hot spot stress in both conditions, and the influence laws were largely the same. With the increase of weld size, the brace-side SCF plunged when the chord- size weld size remained the same, but the chord-side SCF changed slightly when the brace-side weld size was constant. Brace-side and chord-side SCF declined when the brace-side and chord-side weld sizes increased by the same amount. The recommended weld sizes are consistent with the relevant specifications and safe and simple to apply in actual engineering. T F