Friday, 28 August 2015

Tips & Tricks

"Two level model diagnostic tool in ConSteel 9"

In ConSteel there is a possibility to perform a model check on the structure to reveal modelling errors. This model check or diagnostics can be separated to First and Second level model diagnostics:

The First level diagnostics runs automatically before starting the analysis. It is performed on the generated finite element mesh, and it covers the following checks:
   -overhang of line loads and line supports
   -point loads and point supports are not on the model
   -overlap of surface members
   -overlap of bar members
   -very small distance between points or lines of surfaces, bars, loads or supports (the limit distance can be set in the Options >> Diagnostics menu)

The Second level diagnostics can be initiated manually, at any time during the modelling stage to examine the current state. The function can be launched by clicking the View >> Diagnostics... button. It is performed on the user model, where basic requirements for performance of a model are controlled, and it covers the following checks:
   -existence of loads on the structure
   -existence of support on the structure
   -length of bars, line loads and line supports
   -value for the thickness and finite element size for surface members
   -overlap, length and compatibility of haunches
   -multiple supports on the same place
   -compatibility of tension bars
   -hinges on free beam ends
   -unproperly supported model parts

It is advisable to perform a second level diagnostics after the modeling of the structure to reveal errors occurred by inaccuracies of the model building. After these errors had been fixed, it is OK to proceed to the analysis, which will automatically trigger the first level diagnostics. If it still reveals model errors, it is easier to handle them if all of the problems from second level diagnostics had been fixed.

There are two kinds of diagnostic messages:
ERRORS: They make the calculations impossible or meaningless to execute so the detected errors stops further calculations.
POSSIBLE ERRORS: The warnings allows the calculations but they can influence the results.


By clicking on any of the object name in the tree structure, and pressing the SELECT button, the selected object will be highlighted in the model graphic. The selected object can be erased by pressing DELETE button, or it can be modified with the regular geometric operations.

To see the use of the diagnostic tool, please watch our tutorial video below, or cick on the link below:
Two level model diagnostic tool in ConSteel 9


To read more about the Diagnostics in ConSteel, please see the following chapters from the manual:
   1.2.3 The menu
   1.2.7 The windows of object tree, diagnostics results and object properties
   7.3 Model check (diagnostics)

Tuesday, 11 August 2015

FAQ

"What is the difference between Global stability check, and Member check function? How can I get the buckling length of a certain member?"


In Eurocode 1993-1-1, and so in ConSteel, there are 3 methods to verify the stability of a model:

  • Imperfection approach (described in Section 5.2 and 5.3)
    • The structural model is subjected to appropriate geometrical imperfections and after completing a second order analysis, only the cross section resistances need to be checked
  • Isolated member approach ( described in section 6.3.1, 6.3.2 and 6.3.3)
          The method is based on two essential simplifications:
    • Structural member isolation: The relevant member is isolated from the global structural model by applying special boundary conditions (supports, restraints or loads) at the connection points which are taken into account in the calculation of the buckling resistance
    • Buckling mode separation: The buckling of the member is calculated separately for the pure modes: flexural buckling for pure compression and lateral-torsional buckling for pure bending. The two effects are connected by applying special interaction factors.
  • General method (described in section 6.3.4)
          The basic idea behind the general method is that it no longer isolates members and separates             the pure buckling modes, but considers the complex system of forces in the member and                     evaluates the appropriate compound buckling modes. The method offers the possibility to                   provide solutions where the isolated member approach is not entirely appropriate:
    • The general method is applicable not only for single, isolated members, but also for sub frames or complete structural models where the governing buckling mode involves the complete frame.
    • the general method can examine irregular structural members such as tapered members, haunched members, and built up members.
    • The general method is applicable for any irregular load and support system where separation into the pure buckling modes is not possible.
However, in pure cases (pure compression, or pure bending), buckling length calculated from general method can be equated with isolated member approach. In the following, a "how to" example will be shown on a pure compression column:

 Example:

Determination of alpha critical factor with buckling analysis:
Alpha critical factor: Minimum amplifier for the in plane design loads to reach the elastic critical resistance of the structural component with regards to lateral or lateral torsional buckling without accounting for in plane flexural buckling.


Elastic critical normal force can be expressed, with the multiplication of alpha critical, and Ned. With a substitution to the Isolated member approach formula, buckling length can be calculated. 
In this case, the buckling length is 2088mm, which (with the 3000 mm whole column length) gives back the well known 0,7 effective length factor by the buckling shape of a top-pinned, bottom-fixed column.

Summation:

If you want to read more in this topic, please click the following link:

Thursday, 6 August 2015

Tips&Tricks

User defined Standards


Although, we always consider the demands of our users during the development of ConSteel, it is possible to run into a problem, that does not have a direct solution. Our principle in these situations, is to give an alternative solution for the actual problem. The next feature of ConSteel is also built on this effort.

In ConSteel, a great variety of National Annexes can be used for structure design. The Standards menu provides a great opportunity to view existing annexes. In case if you can not find the annex you wish to use, you are still able to define a new, custom one, in an easy way.

The following annexes are available in ConSteel 9 at the moment:
Recommended, German, Hungarian, Dutch, Finnish, Singapore, Portuguese, Swedish, Austrian, Polish, Greece and Spanish



Standards dialog can be opened by clicking the "Standards" menu in ConSteel.
On the left side of the Standards dialog, the standard tree is shown. By selecting a standard, all of the parameters, combination factors, safety factors are sorted, and they can be checked by chapters.

If changes in the parameters of an existing annex is necessary, it can be performed, by selecting the existing annex which is the most similar in parameters to our missing annex, and then by clicking the "New" button on the bottom left side of the dialog. With this action, a User defined annex will be generated, what has the same parameters like the selected annex had before clicking the "New" button. The difference is that the parameters of this copy of an annex are editable, and can be redefined by the user.

Unlimited number of user defined annexes can be created, and they will all appear under the User component of the Standards tree. They can be edited at any time later.

 By default they will be saved to the following file:  Documents\ConSteel\UserSandard.xml