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D5.C.1 General Description

The main steps in performing a design operation are:

  1. Selecting the applicable load cases to be considered in the design process.
  2. Providing appropriate "Parameter" values if different from the default values.
  3. Specify whether to perform code-checking and/or member selection.

These operations can be repeated by the user any number of times depending on the design requirements. The "Parameters" referred to above provide the user with the ability to allocate specific design properties to individual members or member groups considered in the design operation.

D5.C.1.1 Eurocode 3 - EN 1993-1-1:2005 (EN 1993)

The EN 1993 version of Eurocode 3, Design of steel structures, Part 1.1 General rules and rules for buildings (EN 1993) provides design rules applicable to structural steel used in buildings and civil engineering works. It is based on the ultimate limit states philosophy that is common to modern standards. The objective of this method of design is to ensure that possibility of failure is reduced to a negligible level. This is achieved through application of safety factors to both the applied loads and the material properties.

The code also provides guidelines on the global methods of analysis to be used for calculating internal member forces and moments. STAAD uses the elastic method of analysis which may be used in all cases. Also there are three types of framing referred to in EC3. These are “Simple”, “Continuous”, and “Semi-continuous” which reflect the ability of the joints to developing moments under a specific loading condition. In STAAD only “Simple” and “Continuous” joint types can be assumed when carrying out global analysis.

D5.C.1.2 National Annex Documents

Various authorities of the CEN member countries have prepared National Annex Documents to be used with EC3. These documents provide alternative factors for loads and may also provide supplements to the rules in EC3.

The current version of EC3 (EN 1993) implemented in STAAD.Pro adheres to the factors and rules provided in EN 1993-1-1:2005. STAAD.Pro includes the following National Annexes:.

  1. British National Annex [NA to BS EN 1993-1-1:2005]
  2. The Dutch National Annex [NEN-EN 1993-1-1/NB] and
  3. Norwegian National Annex [NS-EN 1993-1-1:2005/NA2008]
  4. French National Annex [Annexe Nationale a la NF EN 1993-1-1:2005]
  5. Finnish National Annex [SFS EN 1993-1-1:2005]
  6. Polish National Annex [PN EN 1993-1-1:2005]
  7. Singaporean National Annex [SS EN 1993-1-1:2005]
  8. Belgian National Annex [NBN EN 1993-1-1 ANB:2018]
  9. Malaysian National Annex [MS EN 1993-1-1]
  10. German National Annex [DIN EN 1993-1-1:2005]
  11. Swedish National Annex [BFS EN 1993-1-1:2005]

The choice of a particular National Annex is based on the value of a new NA parameter that is set when you specify the EN 1993 version of Eurocode 3. Refer to D5.D. European Codes - National Annexes to Eurocode 3 [EN 1993-1-1:2005] for a description of the NA parameter.

Axes convention in STAAD.Pro and Eurocode 3

By default, STAAD.Pro defines the major axis of the cross-section as Z-Z and the minor axis as Y-Y. A special case where Z-Z is the minor axis and Y-Y is the major axis is available if the SET Z UP command is used and is discussed in TR.5 Set Command Specification. The longitudinal axis of the member is defined as X and joins the start joint of the member to the end with the same positive direction.

Eurocode 3, however, defines the principal cross-section axes in reverse to that of STAAD.Pro, but the longitudinal axis is defined in the same way. Both of these axes definitions follow the orthogonal right hand rule.

Bear this difference in mind when examining the code-check output from STAAD.Pro.

Axis convention in STAAD.Pro and EC3

Refer to D5.C.9 Tabulated Results of Steel Design for an example of how this appears when Y is up (default).