Superposition Manager – Combination Rules

Running a design requires design load cases dependent on the selected design code. Compiling these load cases by hand is possible and for some projects and specific calculations such as nonlinear analysis necessary. However, for anything else using an automatic combination and superposition can safe time

This post is the first of three to describe the “SOFiSTiK: Superposition Manager – Combination Rules” task and should help to understand the internal workflow.

When starting a new building project, the “Define Combination” task should be already available in the “Project” tree. Keep in mind; it can be added only once to your project tree. The “Define Combination” task itself is divided into two parts. The left part allows checking your existing combination rules as well as the assigned actions and load cases. The right part let you do your settings.

In this post, we’ll have a look at how to “Insert a New Combination Rule” to your project.

1. Insert new element – Combination Rule

The workflow to create a new combination rule starts in the section “Insert new element”. When hitting the Button “Combination Rule”. An empty combination rule is created in “List Combination Rules”.

2. Number and Name of combination Rule

The numbering of the combination rule isn’t that important when sticking with the graphical user interface. But as more important when using the numerical interface (CADiNP) as you need to refer the combination rule number manually for the superposition. SOFiSTiK assigns the number 100 to the first predefined combination rule. The numbering of the first user-defined combination rule starts as default at 1, but can be changed.

3. Superposition Kind

Creating a combination rule requires to decide what rule should be followed. Depending on the chosen design code different combination options are available. You will find the entire list in MAXIMA user manual chapter 4.2.1, but to mention a few.

The right column refers to the numerical input of MAXiMA and gives you further details about the used equation according to the chosen design code.

Combination TypeNumerical Input (Teddy/CADiNP)
Standard superpositioncorresponds to COMB STAN
ULS fundamental combinationcorresponds to COMB DESI
ULS accidental combinationcorresponds to COMB ACCI
ULS seismic combinationcorresponds to COMB EARQ
SLS quasi-permanentcombination corresponds to COMB PERM
SLS characteristic combinationcorresponds to COMB RARE
SLS frequent combinationcorresponds to COMB FREQ
SLS infrequent combinationcorresponds to COMB NONF

COMB DESI represents equation 6.10, 6.10a and 6.10b according to EN 1990 as shown below. Check as well MAXiMA user manual chapter 2.2 for all formulas.

4. Type of resulting Load Case

This section is quite interesting. The provided list allows you to select independently of the chosen kind of combinations rule a specific type of the result load case.

Besides the default type – the result correlates to the selected superposition kind – assigning the results to a contextless type is possible. It allows to generate results for intermediate purpose or simply to check a combination without a design relevant effect.

5. Number of Resulting Load Case

Although an automatic load case numbering system is implemented; three options are available to affect it.

6. Chevron Button

To confirm and store the modifications in the database, it’s required to click the chevron button.

7. List Combination Rules

Depended on the chosen design code in “SOFiSTiK: System Information” dialog box as well as a correlate (code).ini file located in the installation directory (C:\Program Files\SOFiSTiK\2018\SOFiSTiK 2018) predefined combination rules are available.

The predefined combination rules can be modified and will be indicated by “*” at the combination rule number.

Hitting the right mouse button – within the combination rule list – opens the context menu and provides you with further commands.

I’d like to point out the commands “Reinitialize” and “Delete all and reinitialize”. Both effect deleting all defined combinations in the list as well as in the database. Don’t click them accidentally.

Modifying the mentioned *.ini file is possible, but I don’t recommend doing this unless you are aware how it will affect the results. You’ll find an extract below.

8. Used Design Code

The text line indicates the chosen design code. The design code itself is defined in the SOFiSTiK: System Information dialogue box when starting a new project.

Check as well the related posts

Superposition Manager – Combination Rules – Action
Superposition Manager – Combination Rules – Load Case

SOFiSTiK Version 2018 – 4.1.
MAXiMA User Manual Chapter 4, Interactive Version – WinMAX