Depending on the current FEM-Design module you can do different design calculations for concrete, steel and timber model elements. This chapter summarizes the design possibilities and results by design type.

Design Load

All design calculation works with load combinations and load groups.

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Figure: Design calculation settings

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Although analysis can be run for load combinations and load groups in the same time, design calculation results exist only either for the load combinations or the maximum of load groups.

The Shell design can be done only for load combination, because it based on stability results.

Serviceability load combination is considered only in RC bar and shell design, other design is done just for ultimate load combinations.

Buckling Length Factors

Buckling length is claimed input data of all bar element design (RC/steel/timber columns, beams). The buckling length is determined from the bar length and a factor depends on bar end connections. For typical end conditions (hinged, fixed, cantilever etc.), proposed beta factors are available for flexural buckling.

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Figure: Proposed beta factors for flexural buckling

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Buckling length of a Truss member element is equal to its length, so buckling length of trusses cannot be modified.

The default beta factor is 1.0 for both flexural and torsional buckling.

The defined buckling length fundamentally influences the design results.

Design Groups

Elements having certain common properties can be assigned to a design group, and the members in one group will be designed in the same way. For example, uniform reinforcement (longitudinal bars and stirrups) will be calculated for RC bars assigned to one design group, or the same profile will be designed for each steel bar of a design group, etc.

General terms to be a design group member:

  • Same design element type (beam, column, truss member, plate, wall or timber panel)
  • Same material
  • Same geometry (sizes, profiles etc.)
  • Same design parameters (e.g. base reinforcement)
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Depending on specific cases/element types, additional conditions have to be materialized:

  • Same support conditions
  • Same end/edge connections
  • Same load, etc.

n design mode, click 1585300038207-950.png  to group elements under a name and color.

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Figure: Design group tools

Design group tool provides the following group operations:

  • 1585300060953-250.png  creates a new group,
  • 1585300066233-576.png  edits the properties (name and color) of a selected group,
  • 1585300071552-484.png  adds selected elements to the current group,
  • 1585300076097-239.png  removes selected element from the group,
  • 1585300081808-976.png  is available only in Surface and Punching reinforcement design. A group member has to be set as the “Master” that carries visually the representative applied reinforcement designed uniformly for the group. Only the “Master’s” applied reinforcement is editable; symbolic reinforcement is displayed for the other group members.
  • 1585300087999-843.png  explodes/deletes a selected group.
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The next figures give examples of grouping same type steel bars, concrete slabs and beams.

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Figure: Some design groups of a steel frame

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Figure: Design groups of concrete slabs and beams

User defined filters can be created from design group to modify of the design group member’s structural property in Structure tab.

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From Auto Design to Final Design

FEM-Design covers the whole RC, steel and timber design process by starting with automatic predesign (so-called “Auto design”) for the entire structure and/or by elements/design groups, then by continuing with detailed manual design of the domain structural components and by ending with the final design (so-called “Check”) of the entire structure.

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Figure: From predesign of components till final global design

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Although analysis can be done in one step for the entire structure independently of the element types (concrete, steel and timber), design calculations (and so the design modules) can be run separately by the element types (e.g. one after the other).

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Apply design changes and recalculate: one-click validation of design changes in the current entire model together with analysis and design recalculation according to the new states. But, leaving Design mode, the design changes are always updated in the current model.

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Delete all applied quantity: restores the model state previous to the applied design according to following settings dialog:

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Auto Design

Based on internal forces, utilization check and initial design settings, FEM-Design finds quickly and automatically the most suitable applied quantity depending on the design category and element type. The so-called “Auto design” makes a proposal for reinforcement distribution, for the applied profile, for the panel type, etc.

1585300375597-978.pngAuto design can be done for the whole project with the Calculate > Design calculations > Auto design all structural elements. The fast algorithm uses the default calculation and design parameters of the elements and search for the most suitable applied quantity according to the utilization. Auto design automatically runs Analysis calculations (for Load combinations or Load groups), for Stability etc. depending on the design type: e.g. Steel bar design or Shell design.
1585300380122-988.pngAuto design can be applied for single elements and/or design groups only (without running design for the complete model).

The next table summarizes the initial design parameters and the results of Auto design by design categories and element types.

CategoryElement typeDesign parameterAuto design
RC designBar reinforcement

Steel quality, bar diameter and profile, concrete cover

Bar and stirrup distribution (numbers of bars, spacing)

Surface reinforcementSteel quality, bar spacing, shape settings of the reinforcement regions, possible bar diametersBar distribution, applied reinforcement regions and area, and bar diameter
Punching reinforcement

Steel quality, range of diameters, distribution shape (bended bar, circular stirrup, open stirrup)

Bar and stirrup sizes and distribution
Concealed bar reinforcement**
Steel DesignSteel barRange of cross-sectionsSuitable cross-section
 Shell modelRange of plate thicknessesSuitable plate thickness
 Steel joint design**
 Fire design**
Timber designTimber barRange of cross-sectionsSuitable cross-section
 Timber panelRange of panel typesSuitable panel type
 CLT Panel**
 Fire design**

Table: Input parameters and the results of element-based Auto design

Auto design gives summary tables, which display both the initial design parameters and the recommended (applied) quantities optimized to maximum utilization. All utilization details done by the Eurocode 2, 3 or 5 regulations can be also displayed.

Fast redesign can be started from the table by modifying the design parameters.

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Figure: Summary table of Auto design (Bar reinforcement)

If the program is not able to find suitable parameters from the given/available design parameter range, it sends a warning message and marks the problematic elements/groups.

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Leaving Design mode applies all design changes by updating the current model in order to be considered in a next recalculation. It also invalidates previous analysis results.

In RC modules, Auto design results applied reinforcement that is considered in case of cracked-section analysis.

Manual Design

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Following Auto design, “on-the-fly” fine tuning of applied quantities can be done by elements and design groups. In RC design, Manual design completes the applied reinforcement editing task for both concrete surface and bar elements.

The manual design can be done without calculated analysis results in the following categories:

  • RC design
  • Steel design
  • Timber design
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This function is useful especially at the analysis of an existing building.

CategoryElement typePossible initial dataManual design
RC designBar reinforcementReinforcement come from Auto designApplied reinforcement (longitudinal bars and stirrups)
Surface reinforcementReinforcement come from Auto designApplied reinforcement (top/bottom/middle RC)
Punching reinforcementReinforcement come from Auto designApplied reinforcement (bended bar, circular stirrup, open stirrup)
Concealed bar reinforcement**
Steel DesignSteel bar*Applied cross-section
 Shell model*Applied plate thickness
 Steel joint design**
 Fire design**
Timber designTimber bar*Applied cross-section
 Timber panel*Applied panel type
 CLT Panel**
 Fire design**

Table: Input parameters and the results of Manual design

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The next figure gives an example for the reinforcement design of a concrete beam from starting with Auto design and finishing with detailing (Manual design).

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Figure: Combined RC design

   

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Leaving Design mode applies all design changes by updating the current model in order to be considered in a next recalculation. It also invalidates previous analysis results.

In RC modules, Manual design results applied reinforcement that is considered in case of cracked-section analysis.

Detailed Result

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Utilization results with detailed background calculation formulas (together with Eurocode references), figures and tables can be displayed by single elements or by design groups. Quick navigation is powered with zooming details.

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Figure: Detailed result

1585301397673-603.pngOf course, Detailed result is also available for the analysis (displacement, internal forces, and stresses) of bar elements.
Created by Fredrik Lagerström on 2020/03/27 09:56
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