# Opening older models in newer version

$$Steel connection models designed in older versions of IDEA StatiCa may show differences when you upgrade to the newest version. If you want to know how to avoid such dead ends, please go through this article. Changes in version 20.1 An improved model of contacts The analysis model contains several nonlinearities, among them contacts between plates. The contacts are very strong in compression and extremely weak in tension. However, some stiffness is necessary even in tension to ensure the numerical stability of the model. There were several very rare cases with a large contact area and a large deformation in tension where the tension in contacts consumed a significant portion of set loading. The contact model was improved to maintain the stability of the numerical analysis and limit tensile force in contact to a negligible level. Available in Expert and Enhanced edition. Butt welds upgraded model The size of butt welds was corrected for edge-to-surface butt welds. Previously, the thickness of the thinner of the plates was selected. Now, the thickness of the plate whose edge is used is selected. This may have a very small impact on the results in a negligible amount of older models due to the change of multipoint constraints in the analysis model. When the bigger butt weld is used, the multipoint constraint transfers the force into a larger area on the surface of the connected plate. Available in Expert and Enhanced edition. Bolt bearing distances for Eurocode The new version brings an improved algorithm for calculating the bolt spacing (p1; p2), end (e1), and edge (e2) distances for the Eurocode bearing check. This improvement is mostly relevant for general plate geometries, plates with openings, cutouts, etc.The algorithm reads the real direction of the resulting shear force vector in a given bolt and then calculates the distances needed for the bearing check.The end (e1) and edge (e2) distances are determined by dividing the plate contour into three segments. The end segment is indicated by a 60° range in the direction of the force vector. The edge segments are defined by two 65° ranges perpendicular to the force vector. The shortest distance from a bolt to a relevant segment is then taken as an end, or an edge distance. The spacing distances between bolt holes (p1; p2) are determined by virtually enlarging the surrounding bolt holes by a half of their diameter, then drawing two lines in direction and perpendicular to the shear force vector. The distances to the enlarged bolt holes that are intersected by these lines are then considered as p1 and p2 in the calculation. Available in Expert and Enhanced edition. Connecting plate eccentricity The position of the connected member within the operation Connecting plates has been changed in version 20.1. This has been done due to the whole model assembly in the application Connection and further development in interoperability with the application Member.In version 20.0 and older, the connected member was shifted when the Connecting plate operation was applied so that the member axis was centered with the tongue plate, while the connecting plate was centered with the axis of the bearing member. In version 20.1 and newer, the connected member is no longer shifted in order to keep its position, which means the connecting plate is now shifted and no longer centered with the axis of the bearing member. Any configuration can be achieved by changing the Plate eccentricity parameter as well as the required offset of the diagonal member. Changes in version 20Cleat manufacturing operation refactoringIn the previous version Cleat manufacturing operation sometimes made L cross-section legs swapped, mostly while the members were rotated along the longitudinal axis. From now on, the L sections are positioned correctly, and the legs orientation is kept the same while introducing rotation to the member. The new mechanism behind is based on the new member positioning (by its LCS coordinates - rather then it's Rotations).Local coordinate systems of the members in FEA/CAD applicationsAll member entities in FEA/CAD applications are created in a way that their definition axis has the start and the end. These two points are taken as a vector to define the local coordinate system of the member. In each FEA/CAD application project are these data information stored and can be used during the import. We took advantage of that, and it helps to improve the correctness of our BIM link geometry import. On the other hand, it changes the rules of the game, and the user must pay attention to the way how the model is created in FEA/CAD because it has an impact on the CBFEM Connection model also. We recommend to pay attention while importing from FEA/CAD projects into the version 20, the local coordinate system of the members may change the model to and difference compared to the model imported into the previous versions is eminent. Member application projects compatibilityIDEA StatiCa Member application passes through agile development, especially the data storage architecture and the guided user interface. Based on this it's obvious that the projects created in the older versions may not be correctly opened in version 20 or the application may fail to open them. Please be aware of that and excuse IDEA StatiCa for inconveniency. Changes in older versionsOne of the reasons behind the new GUI is that a lot of engineers were saying: „IDEA StatiCa Connection needs to be more error-proof”. These “errors” are usually related to: Setting the correct length of members – in cases of extremely short or long members, this can hugely influence the results. Since version 9, IDEA StatiCa Connection automatically sets an appropriate length of all members. Welds – stress plastic redistribution is by far the most accurate design method for welds and was introduced in version 7.1. During version 8 – and as a transition period - it was the default method, coexisting with the other evaluation methods. Since version 9, this method is the only option available and the other evaluation methods have been removed, to avoid confusion among the users, as we have seen through our helpdesk. This ensures that all welds in the project are safely designed and complying with the code. We have implemented several control mechanisms for IDEA StatiCa Connection since version 9.0 – automatic-check when the connection is modeled in a recommend way (singularity check, member lengths, their offsets, …). If the connection is not modeled properly, the calculation is interrupted or an error message is displayed. Please be aware that because of all of these improvements, opening projects from previous versions can lead to a different model geometry that may need some further editing.We have also improved meshing of hollow sections members – IDEA StatiCa Connection since version 9.0 generates finer meshing on hollow section members which might lead to slightly different results compared to older versions.We display the compatibility warning on each opening of a project from the older versions:$$