Discrepancy in the cross section converge between Eurocode and British code

[kaiwing.wong]

Greetings, 

I am designing a pier cross section using Eurocode, I have inputs all the loads and the reinforcement. When I analyze the cross section design, it shows failed to converge. However, when I switch to British code, under the same loading and configuration, the cross section can be converged. 

After I switched to British code, I switch back to Eurocode again and the cross section can be converged. Thus, may I know why is there a discrepancy between the cross section converge between Eurocode and British Code. Thank you in advanced for your prompt reply. 

Attached 2 files for your reference. The file named "Pier (Autodesk - 2)" cannot be converged while the file named "Pier (Autodesk)" can be converged after switching to BS and switch back to Eurocode. 

[dave_geeves · Accepted solution]

Hi,

I believe the problem is due to the lack of stability when using the Eurocode rectangular stress block type concrete material, especially on relatively large heavily reinforced sections.  The sudden discontinuity  in stress at the bottom of the block will often cause problems in convergence.  f you change the material to either the bi-linear type or the rectangular/parabola type ( as in the British Standards) then the solution seems to be ok.

I hope this has helped, and if it has please mark my reply as a solution so that others may benefit.  Thanks

Kind regards

Dave Geeves

[kaiwing.wong]

Many thanks. Hope my post could help others in this forum.