PSI - Issue 5

Zuheir Barsoum et al. / Procedia Structural Integrity 5 (2017) 1401–1408 Zuheir Barsoum / Structural Integrity Procedia 00 (2017) 000 – 000

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Fig 3. Load capacity calculation on different section for a butt weld.

3. Design Codes and Standards

According to Eurocode 3 and AWS D1.1. load carrying capacities should be calculated on three different section, for example on a butt weld as illustrated in fig 3. Fig 1a shows the two section where the load capacity should be calculated on fillet weld. Both standards allow the use of under-matched filler materials. In case of fully penetrated joints, section A-A is the weaker section. Both standards follow different formulae and safety factors to calculate load carrying capacity of the weld. Here only the directional method in Eurocode will be described, where the load carrying capacity is evaluated according to the following equations:

The load carrying capacity of a partially penetrated fillet weld is given as follows:

In case of butt welds, α = 90 deg. For partially penetrated butt welded joints contribution from possible eccentric loading is also considered in the calculations. In AWS D1.1, for fully penetrated butt welds, it is recommended to consider the base plate load carrying capacity as the load carrying capacity of the joint. For partial penetrated butt welds, the allowable stress is 0.3x the nominal tensile strength of the weld metal, but not more than 0.6x the yield strength of the base metal. This assumption leads to safety factors ranging from 2.2 for shear forces parallel to the longitudinal axis of the weld to 4.6 for forces normal to the axis under service loading. Vickers hardness testing has been done on the fillet and butt welds, Changes in the hardness was observed in the HAZ in comparison with the base material. In general, a joint with under-matched and matched weld filler material a lower hardness in the weld metal and the peak value can be observed as compared to over-matched filler material. The testing was carried out in a Schenk 250 kN machine with a constant displacement rate of 2 mm/min and strain gauges to monitor the force-displacement Khurshid et al (2012). Ultimate strength capacity vs. displacement graphs obtained are presented in fig 4a for fully penetrated joint with different filler material and in fig 4b for partially penetrated fillet welds. Failure for the full penetration fillet welds occurred in the web plates of the steel grade S600 MC while for the partial penetrated fillet welds failure occurred on the welds. Fig 4 c shows examples of the different failure locations for the fillet welds. 4. Testing and analysis