Structural FEA Software RFEM 5 | Automatic Generation of Combinations

Standards

The General Data dialog box includes a wide range of standards and the option to create combinations automatically.  The following standards are available:

•  EN 1990: 2002
•  EN 1990 + EN 1995: 2004 (timber)
•  EN 1990 + EN 1991-2; Road bridges
•  EN 1990 + EN 1991-3; Cranes
•  EN 1990 + EN 1997
•  DIN 1055-100: 2001-03
•  DIN 1055-100 + DIN 1052: 2004-08 (timber)
•  DIN 1055-100 + DIN 18008 (glass)
•  DIN 1052 (simplified) (timber)
•  DIN 18800: 1990
•  ASCE 7-10
•  ASCE 7-10 NDS (timber)
•  ACI 318-14
•  IBC 2015
•  CAN/CSA S 16.1-94: 1994
•  NBCC: 2005
•  NBR 8681
•  IS 800: 2007
•  SIA 260: 2003
•  SIA 260 + SIA 265: 2003 (timber)
•  BS 5950-1: 2000
•  GB 50009-2012
•  CTE DB-SE

For the European standards (EC), the following National Annexes are available:

•  DIN EN 1990/NA: 2009-05 (Germany)
•  NBN EN 1990 - ANB: 2005 (Belgium)
•  BDS EN 1990: 2003/NA: 2008 (Bulgaria)
•  DK EN 1990/NA: 2007-07 (Denmark)
•  SFS EN 1990/NA: 2005 (Finland)
•  NF EN 1990/NA: 2005/12 (France)
•  ELOT EN 1990: 2009 (Greece)
•  UNI EN 1990/NA: 2007-07 (Italy)
•  IS EN 1990: 2002 + NA: 2010 (Ireland)
•  LVS EN 1990: 2003/NA: 2010 (Latvia)
•  LST EN 1990/NA: 2010-11 (Lithuania)
•  LU EN 1990/NA: 2011-09 (Luxembourg)
•  MS EN 1990: 2010 (Malaysia)
•  NEN EN 1990/NA: 2006 (Netherlands)
•  NS EN 1990/NA: 2008 (Norway)
•  ÖNORM EN 1990: 2007-02 (Austria)
•  NP EN 1990: 2009 (Portugal)
•  PN EN 1990/NA: 2004 (Poland)
•  SR EN 1990/NA: 2006-10 (Romania)
•  SIST EN 1990: 2004/A1: 2005 (Slovenia)
•  SS EN 1990: 2008 (Singapore)
•  SS EN 1990/FSO 2010: 28 (Sweden)
•  STN EN 1990/NA: 2009-08 (Slovakia)
•  UNE EN 1990 2003 (Spain)
•  CSN EN 1990/NA: 2004-03 (Czech Republic)
•  BS EN 1990/NA: 2004-12 (United Kingdom)
•  CPM EN 1990/NA: 2011 (Belarus)
•  CYS EN 1990: 2002 (Cyprus)

Load Cases / Action Types

In the "Edit Load Cases and Combinations" dialog box, you can create and edit load cases as well as generate action, load, and result combinations. It is possible to assign various action types to the individual load cases in accordance with the selected standard. If several loads have been assigned to one action type, they can act simultaneously or alternatively (for example, wind from the left or right).

Combination Expressions

For the combination of actions in the ultimate and the serviceability limit state, you can select various design situations according to the standard (for example, ULS (STR/GEO) - permanent/transient, SLS - quasi-permanent, and others). Furthermore, there is the option to integrate imperfections in the combination and to determine load cases that should not be combined with other load cases (for example, construction load for roof not combined with snow load).

Accidental Design Situation

The "Accidental" design situation automatically considers accidental actions such as earthquake, explosion loads, collisions, and others. When using German standards, you can select the "Accidental - Snow" design situation to consider the North German Plain automatically as well.

Reduction of Automatically Generated Combinations

There are three options to reduce the number of combinations. The first two procedures are only available for the generation of load combinations, not for result combinations.

The first option allows for automatic analysis of all load case results (internal forces, deformations, and so on) of selected elements. Then, the program will generate only those combinations that include the load cases producing a maximum or minimum. In addition, you can define a maximum number of relevant load cases, or neglect load cases with a very small contribution to the maximum and minimum values.

The second option allows for automatic evaluation of generated temporary or user-defined result combinations. Then, only the governing load combinations are created.

The third option to reduce the number of generated combinations is to classify only selected actions as leading actions.

Action Combinations

The actions are automatically superimposed in accordance with combination expressions and then displayed as "action combinations". It is possible to define which action combinations will eventually be used for the generation of load or result combinations. Based on the created action combinations, you can estimate how the combination expressions affect the number of combinations.

Load Combinations

The load cases included in load combinations are added together and then calculated in consideration of the corresponding factors (partial safety and combination factors, coefficients regarding consequence classes, and others). The load combinations can be created automatically in compliance with the combination expressions of the standard. It is possible to perform the calculation according to the linear static analysis, second-order analysis, or large deformation analysis, as well as for postcritical failure. Optionally, you can define whether the internal forces are relative to a deformed or non-deformed structure.

Result Combinations

The load cases included in result combinations are calculated first. Then, the results are superimposed by taking into account the corresponding factors. In the result combinations, you can superimpose the results of load cases and load combinations as well as other result combinations. Internal forces are added together by default. However, there is the option of a square addition, which is relevant for dynamic analysis.

Modifying Stiffness / Considering Initial Deformations

In the individual load cases or combinations, there is the option to modify the stiffnesses of materials; cross-sections; nodal, line and surface supports; and member and line hinges for all or selected members. Furthermore, it is possible to consider initial deformations from other load cases or load combinations.