Butt Weld Design
The Steps 🪜 You Have To Follow
Hi friends, 👋👋
We continue diving deeper into structural steel design. And today we’ll cover the calculation steps of butt welds.
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So here are the steps, we need to follow:
Define the type of butt weld
Define material and geometry properties
Calculate the stresses in the weld
Calculate the design resistance of the weld
Check utilization
So let’s get started. 🚀🚀
1. Define the type of butt weld
Eurocode defines 3 different types of butt weld and because the calculation of these types is different, we need to know the difference:
Full penetration butt welds:
This type of butt weld basically has the same or bigger thickness than both of the connecting plates. Therefore, the strength of the weld is higher than of the 2 plates. This is great news for us designing the weld: We don’t have to verify anything. 😮🙌
Partial penetration welds (see image of introduction):
The partial penetration weld doesn’t penetrate the thickness of the 2 plates. This type of butt weld we have to verify. ☝️☝️ We can either use the directional or the simplified method according to Eurocode EN 1993-1-1.T-butt joint:
T-butt joints can either be categorized as full or partial penetration welds. If anom.1 + anom.2 > t the joint is categorized as full penetration weld, and then we don’t have to verify the welds.
However, if anom.1 + anom.2 < t, then the weld is a partial penetration weld, and we have to run the calcs.
So in the following show the calculation of a partial penetration butt weld. 👇👇
2. Material and geometry properties
Next, we need to define some properties such as
Throat thickness a
Steel beam plate width and height
Moment of inertia of the weld
Length of weld
Ultimate tensile strength
Correlation factor
Partial safety factor
3. Stresses in the weld
Now, in order to calculate stresses, we need internal forces. You calculate these either by hand or with a structural analysis software.
Then, we can calculate the stresses:
4. Design resistance stress of the weld
The design resistance stress is given in EN 1993-1-8 4.5.3.3 as:
5. Utilization
Finally, checking the utilization ratio:
Conclusion
Designing butt welds isn’t that difficult, is it? We find the internal forces acting in the connection, define geometric and material properties, and calculate the stresses in the weld and the resistance stress. That’s it.
Hope this guide helped you understand welds better.
See you next week for another structural guide.
Cheers,
Laurin. ✌️✌️