17 Feb Steel joints with PFCs: problem solved!
Among other unique advantages, IDEA StatiCa provided a complete solution to a problem that existed for many years: connections that incorporate PFC sections (Parallel Flange Channels – or UPN in Eurocodes) . Although competing software seem to support PFCs for very simple cases like fin plate connections, more difficult cases such as moment resisting connections, or complex geometries, are not covered at all. Some of our customers have asked us in the past why is this the case with other software and how IDEA StatiCa covers this gap.
Actually, the problem lies deep in the heart of the component method as drafted in EN 1993-1-8 (part for steel connections) as the provided information is mainly towards I sections, leaving other section types in the dark.
To explain it more, let’s have a look at the two connections displayed below:
A PFC and an I section of about the same size and mechanical properties are connected to an unstiffened column with the same end-plate. For the average component method user, applying the Eurocode provisions on the PFC connection is impossible.
To get some more in-depth information, we asked an expert in our team to provide us his opinion on how this PFC connection could be solved ‘by hand’. He said that in such case the bolts are standard, but the big challenge is the end-plate. And although an experienced engineer would feel confident about the problem, the solution would probably be to neglect two of the bolts positioned away from the PFC, and use yield line theory to calculate the effective lengths for end plate components, as Eurocode formulas just do not apply. So, the solution would be quite non-standard and would at least raise questions if it was applied in a usual project.
IDEA StatiCa advantages
All these ‘grey’ areas around PFCs resisting moments, magically disappear with IDEA StatiCa, since our generalised models can work around the code limitations and provide insight for connections with channel sections in the same way as they do with I sections. Even in the case of end plates. Moreover, due to this versatility, we support any type of cross section you can imagine.
In the analysis comparison below, we can see that with the same load, the same more or less mechanical properties of the cross-section, and the same end plate, the PFC model has a failure in the top weld, probably because of the smaller length and the eccentricity of the cross-section.
Last, all eccentricities are naturally accounted, and you don’t have to modify your loads in any way to make this work. See below the un-stiffened column flange deformation reflecting the eccentric connection of the PFC beam.