Steel Design
Fast auto design and check are available to find the most suitable steel bar profiles. All section shapes and classes - including class 4 profiles (slender sections) - can be checked for utilization. When modeling steel bars with 3D steel shell components, an auto design finds the proper thickness of the shell elements.
The table summarizes the available steel design features by FEM-Design module.
Design element type | Design feature | |||
Steel Bar | Auto design | |||
Manual design | ||||
Shell Model | Auto design | |||
Manual design |
Table: Steel design features by FEM-Design module
Steel Bar
Global Auto (steel bar) design (Calculate > Design calculations > Auto design all structural elements) finds the most suitable cross-section (from the profile range set at Auto design > Parameters) for all steel bars (columns, beams and truss members) based on their buckling length, stiffeners, calculation parameters, internal forces and detailed utilization calculations. With Manual design you can run quick utilization check for given profiles by bar elements and/or design groups. You can also do quick Auto design by elements and design groups only instead of global design. Of course, any number of design cycles is executable, so the global Auto design can be combined with both previous and additional element-based Auto designs.
No. | Global steel bar design | Element-based steel design | Combined steel design |
1 | Calculation parameters | Global Analysis | Calculation parameters |
2 | Design group | Calculation parameters | Design group |
3 | Auto design > Parameters | Design group | Auto design > Parameters |
4 | Global Auto design | Auto design > Parameters | Global Auto design |
5 | Documentation | Auto design by elements | Auto design > Parameters |
6 | Manual design by elements | Auto design by elements | |
7 | Apply design changes | Manual design by elements | |
8 | Global Check | Apply design changes | |
9 | Documentation | Global Check | |
10 | Documentation |
Table: Recommended steps by design alternatives
Initial Calculation and Design Parameters
All bar design calculations needs internal forces from Analysis calculations applied for Load combinations or Load-groups, Buckling length and initial design settings defined by Design calculation parameters.
Figure: Design calculation parameters
The flexural buckling curves (EN1993-1-1: 6.3.1.2) can be specified for each steel bar in Calculation parameters dialog or the user can let the program to calculate it as in the previous versions by selecting “Auto” option.
The method for considering imperfections of bars has to be selected, there are three types:
- Ignore 2nd order analysis: The internal forces comes from the 1st order results.
- Consider 2nd order analysis, if available: The internal forces comes from the 2nd order results.
- 2nd order internal forces + 1st order design: The internal forces comes from the 2nd order results, but the design calculation will be linear.
Figure: Setting calculation parameters
For steel bars with varying section the “Auto” option cannot display the automatically calculated curve, since it is determined during the design calculation. |
When the section of a steel bar is modified, buckling curve options of the calculation parameter is reset to “Auto” |
When buckling curve is calculated automatically, applied section is considered, if it exist. |
Convergence criteria and the maximum number of iteration steps can be set for effective cross-section calculation of Class 4 steel bar section in Calculation parameters dialog.
In some cases the iteration for effective cross-section fails because of the too strong convergence criteria. In this case reducing its factor or increasing the number of the iteration steps may solve the problem. |
Lateral torsional buckling can be calculated using the formulas to general case instead of using the simplified method.When the general method is used for lateral torsional buckling calculation, the position of the load needs to be specified as well. Calculation method of the kij interaction factors can be specified by selecting the design configuration option from the ribbon. |
For lateral torsional buckling the program can separate to top flange and bottom flange stability loss. In the following picture the top flange and it’s corresponding force is red and the bottom is blue.
Beta factors for all 4 direction-stability loss method are separate from each other.
To copy buckling lengths from one bar to another use the Copy buckling length command and:
- Select the types to copy
- Select the source bar
- Select the destination bar
Stiffeners can be added manually to steel bars at any time during design (e.g. before Auto design, or between Auto design and final Check). Stiffeners can be defined element by element, but they can be copied among bar elements. Stiffener definition tools are:
|
You can increase the number of stiffeners in more steps, if you inactivate (Do not delete the original).
Figure: Stiffeners
Auto Design
Global Auto design gives utilization results and suitable profiles for all steel bars of the current project. |
Figure: Global Auto design and utilization result
The recommended profile names can be displayed on screen by showing the “Steel bar, applied quantity” object layer, or click Design tool of the Auto design and the parameters together with utilization results are available in table format. Utilization as colored figure (color palette) can be displayed by selecting New result > Steel bar > Utilization. |
Variable cross-section steel bars can’t be designed, just checked. |
Applied profiles are displayed in blue in the Utilization table, if they are assigned to the steel bars during design, otherwise black color represents the original/initial profiles.
Element-based Auto design finds the most suitable profile of steel columns, beams and bars for selected unique or grouped members only from a range of available profiles defined by Parameters. The design utilization can be limited between 10% and 100% with Limit utilization. |
Figure: Range of available profiles for design
To run element-based design for the load combinations or the maximum of load groups, select the required members and/or group with the Auto design command and click Design tool. The quick process results recommended profiles and their utilization. Check the Display table box to have a look at the overall design results (see the figure before).
The upper table shows the design efficiency and the maximal utilization of the designed single members and groups based on the given design parameters. The bottom table displays the utilization details of the bar or the members of the group selected in the upper table.
Meaning | Note | |
Suitable profile is available | ||
Suitable profile is not available | Modify the range of available profiles or steel materials | |
Suitable profile is available, but the utilization is over the Limit utilization | ||
Group | ID of a single bar or a group name | |
Design parameters | The defined range of available profiles | |
Applied profile | Profile currently assigned to the bar | |
Max | Max. utilization of a single bar or the significant member of a group | |
Min | Max. utilization of the less significant group member | |
Bar | ID of a single bar or a group member | |
RCS | Resistance of cross-section: the maximum utilization from all strength calculations | According to Eurocode 3: 6.2.3 - 6.2.10 |
FB | Utilization for flexural buckling | According to Eurocode 3: 6.3.1 |
TFB | Utilization for torsional-flexural buckling | According to Eurocode 3: 6.3.1 |
LTB | Utilization for lateral torsional buckling | According to Eurocode 3: 6.3.2.4 |
SB | Utilization for shear buckling | According to Eurocode 3: 1-5: 5 |
IA | Interaction (between normal force and bending) | According to Eurocode 3: 6.3.3 |
Table: The meaning of symbols, design parameters and utilization results
Quick redesign can be done inside the Utilization table:
- Select a bar or a design group in the upper table.
- Modify the range of available profiles for the select element under Parameters.
- Click Design.
Save /load default sections
For each section type (e.g. IPE, HEA, CHS, etc.) a set of sections can be saved/loaded as default.
This will only work with one type cross-section (e.g. only HEA, or only KKR) selected. Otherwise, with Save command, the user can save a set of arbitrary sections into a file, and use them later for another model by Load command.
Manual Design
With Manual design quick utilization check can be done for given steel profile and for selected steel beam, column, bar or design group only. Just, choose the load type (load combination or load group) and a profile name from the drop-down lists and select a bar, bars or group, and program displays detailed utilization results in table format. |
The meaning of the utilization components, the table content and features are the same as written before at Auto design. The program use the chosen profile for all selected bar elements. |
Figure: Quick check by Manual design
Detailed Result
Utilization of steel bars can be displayed in the following cases:
- After global Auto design, you can display utilization of all steel bars checked for the recommended profiles.
- When running element-based Auto design, utilization can be displayed by designed elements.
- After Manual design, element-based Check displays utilization for selected elements.
- After global Check done for all bar elements having final cross-section.
No. | Global Auto design | Element-based Auto des. | Element-based Check | Global Check |
1 | Calculate > Design calculation > Auto design all structural elements | Auto design | Auto design and/or Manual design | Auto design and/or Manual design |
2 | New result > Steel bar | New result > Steel bar | Check | Apply changes |
3 | New result > Steel bar | Calculate > Design calculation > Auto design all structural elements | ||
4 | New result > Steel bar |
Table: Steps of displaying steel bar utilization by different design cases
Utilization displayed with New result appears for all designed bars. The utilization components for a bar/design group can be displayed with Detailed result. |
Detailed result opens a new window in the current project after selecting a bar/group member, which displays:
- Input data
The figure displays the applied steel cross-section with its main calculation and material parameters.
Figure: Applied cross-section
- Detailed calculation formulas
Calculation details and final values are collected by checking types:- Shear resistance (Eurocode3: 1-1: 6.2.6, 6.2.8),
- Torsional resistance (1-1: 6.2.7),
- Shear stress (1-1: 6.2.6),
- Normal stress (1-1: 6.2.1),
- Normal capacity (1-1: 6.2.1),
- Flexural buckling (1-1: 6.3.1),
- Torsional-flexural buckling (1-1: 6.3.1),
- Lateral-torsional buckling (1-1: 6.3.2.4),
- Interaction between normal force and bending (1-1: 6.3.3.) and
- Shear buckling (1-5: 5).
The proper results are displayed in green, while the red result warnings you to repeat design with new bar properties. The content of the utilization checks depends on Display options. Not relevant checks can also be hidden.
Figure: Utilization checks and formulas
- Summary graph
Summary graph is displayed with legend by default. Numeric values can be inquired in the calculation sections (set by Design calculation parameters).
Figure: Utilization summary
Tabmenu contains the following tools and settings:
- Selection of element to display
You can choose a unique or a design group member from the drop-down lists to display its detailed results mentioned before. Each row displays the ID and the maximum utilization of a member. In case of a design group, “Maximum” means each check is displayed for the significant member having the maximum utilization for that check.
Figure: Selection of a unique or a group member - Selection of design load
Depending on steel design was done for load combinations or load groups, a load combination or the maximum or a significant component of load groups can be selected for detailed results. Each row displays the name of the load combination/load group component and its utilization effect. “Maximum” means each check is displayed for the significant load combination or component of load groups having the maximum utilization for that check.
Figure: Selection from design loads - Auto design
Quick Auto design can be done for the currently displayed unique/group member. Its design parameters can be set/modified in the appearing dialog, and then clicking OK starts steel design that updates all detailed result figures and formulas. - Manual design
Manual design can be launched directly for the currently displayed unique member /group. - Display options
The content and the appearance of the detailed result can be set with Display options. You can show only the final equation without details of the different checks (Hide details).
Figure: Display options of Detailed result - Go to
Navigate in the detailed result window by selecting the required design type in the drop-down list. It is useful when you are in zoomed view.
Click Tools > Add view to document to place all figures, fomulas and summary table or specified details only into Documentation.
Fire design for steel bars
Fire design gives the opportunity to check and design steel bars for fire effects according to EN 1993-1-2.
Launch Steel design/ Steel bar, fire design . To start Fire design it needs some new input data of the bars, and a special load combination and/or load group must be defined.
- A „+Fire” type load case has to be defined in the Load cases dialog.
- For maximum of load groups calculations, an accidental load group must be defined that contains the „+Fire” type load case.
- For maximum of load combinations calculations, accidental load combinations must be defined that contains the „+Fire” type load case.
- The effects (internal forces) are calculated from accidental load combinations, where fire is the accidental effect. Resistance of bar is calculated by using reduced yield strength and elasticity modulus for steel at the elevated temperature.
Fire design contains Calculation parameter, Check, Design group, Auto design and Manual design commands.
Calculation parameter
Explanation of data in calculation parameters are in EN 1993-1-2:3, 4 and EN 1992-1-2:3.
„Deflection criterion is essential” option is available for Danish national annex only.
Check
It works in exactly the same way as in case of steel bar design.
Design group
It works in exactly the same way as in case of normal steel bar design, except that fire design parameter and fire design calculation parameter of two bars must match to be placed into the same design group.
Auto design
There are two design options:
- Design for fire protection material
The design parameter contains the fire protection material, which can be selected from a library (see later). Its minimal and maximal thickness and an increment value, which is used by the automatic design procedure to find the minimal necessary thickness of the protection material, can be given by the User - Calculate maximum temperature
The Temperature step for maximum temperature calculation can be defined by the User.
Limit utilization can also be set in the Steel bar - fire design parameter dialog
Manual design
Fire protection material (from a library, see later), its thickness, or the Maximum member temperature can be selected in Steel bar, fire protection dialog for Manual Design..
Fire protection material library
It is available by clicking on „Edit library…” item in the material list of fire protection parameter in Auto and Manual design dialogs.
Results
Utilization results are available to display on the model and to list.
A new result “Max. of combinations/Bar, Combined utilization summary” is available, where the maximum utilization of steel bars for both normal and fire check is displayed
Shell Model
In FEM-Design, a steel bar can be modeled as a real 3D element defined from steel plates.
To convert a bar element to 3D shells apply the Steel bar, shell model tool of the Tabmenu. |
Global Auto (Shell model) design (Calculate > Design calculations > Auto design all structural elements) finds the most suitable thickness (from a thickness range set at Auto design > Parameters) for all steel plates of the shell model based on internal forces, stability check and detailed utilization calculations. With Manual design you can run quick utilization check of given thickness values for selected shell models or their design groups. You can also do quick Auto design by shell elements and design groups only instead of global design. Of course, any number of design cycles is executable, so the global Auto design can be combined with both previous and additional element-based Auto designs.
No. | Global steel bar design | Element-based steel design | Combined steel design |
1 | Structure > Steel bar,shell model | Structure > Steel bar,shell model | Structure > Steel bar,shell model |
2 | Design group | Global Stability analysis | Design group |
3 | Auto design > Parameters | Design group | Design Parameters |
4 | Global Auto design | Auto design > Parameters | Global Auto design |
5 | Documentation | Auto design by elements | Auto design > Parameters |
6 | Manual design by elements | Auto design by elements | |
7 | Apply design changes | Manual design by elements | |
8 | Global Check | Apply design changes | |
9 | Documentation | Global Check | |
10 | Documentation |
Table: Recommended steps by design alternatives
Stability analysis is required to get utilization check of steel bar-shell models. Global Auto design automatically runs stability analysis for the entire structure. |
Auto Design
Global Auto design gives utilization results and suitable thickness for all steel plates of shell models.
Figure: Global Auto design and utilization result
The recommended thickness values can be displayed on screen by showing the “Steel bar, shell model, applied quantity” object layer, or click Design tool of the Auto design and the thickness values together with utilization results are available in table format. Utilization as colored figure (color palette) can be displayed by selecting New result > Steel bar, shell model > Utilization. |
Applied thickness values are displayed in blue in the Utilization table, if they are assigned to the steel shell parts during design, otherwise black color represents the original/initial thickness.
Element-based Auto design finds the most suitable thickness of steel plates for selected unique or grouped shell models only from a range of available thicknesses defined by Parameters. |
Figure: Range of available thickness values for design
To run element-based design for the load combinations, select the required shell element and/or element group with the Auto design command and click Design tool. The quick process results recommended thickness values and the utilization of the shell model elements. Check the Display table box to have a look at the overall design results (see before).
The upper table shows the design efficiency and the maximal utilization of the designed single element and groups based on the found thickness values. The bottom table displays the utilization details of the shell model element or the members of a group selected in the upper table.
Meaning | |
Suitable thickness is available | |
Suitable thickness is not available (Modify the range of available thicknesses or steel materials.) | |
Group | ID of a single element or a group name |
Design parameters | The defined range of available thicknesses |
Applied thicknesses | Thickness currently assigned to the shells |
Max | Max. utilization of a model element or the significant member of a group |
Min | Max. utilization of the less significant group member |
Bar | ID of the designed single bar or a group member |
Stress | Stress utilization |
FBS | Utilization for flexural buckling around the stiff axis |
FBW | Utilization for flexural buckling around the weak axis |
TB | Utilization for torsional buckling |
LTB | Utilization for lateral torsional buckling |
LB | Utilization for local buckling |
Table: The meaning of symbols and utilization results
Quick redesign can be done inside the Utilization table:
- Select a bar or a design group in the upper table.
- Modify the range of available plate thicknesses for the select element under Parameters.
- Click Design.
Manual Design
With Manual design quick utilization check can be done for custom (also different) thickness values of selected steel plates (or their groups). Just select steel plate(s) and set a thickness value in the appeared dialog. Run Check calculation to run and display utilization check for the modified plates according to their new thickness values. |
The meaning of the utilization components, the table content and features are the same as written before at Auto design. |
Figure: Quick check by Manual design
Detailed Result
Utilization of steel bar-shell models can be displayed in the following cases:
- After global Auto design, you can display utilization of all steel shell models.
- When running element-based Auto design, utilization can be displayed by designed elements.
- After Manual design, element-based Check displays utilization for selected elements.
- After global Check done for all bar-shell elements having final plate thicknesses.
No. | Global Auto design | Element-based Auto des. | Element-based Check | Global Check |
1 | Calculate > Design calculation > Auto design all structural elements | Auto design | Auto design and/or Manual design | Auto design and/or Manual design |
2 | New result > Steel bar, shell model | New result > Steel bar, shell model | Check | Apply changes |
3 | New result > Steel bar, shell model | Calculate > Design calculation > Auto design all structural elements | ||
4 | New result > Steel bar, shell model |
Table: Steps of displaying steel bar-shell model utilization by different design cases
Utilization displayed with New result appears for all designed bar-shell models. The utilization components for an element/design group can be displayed with Detailed result. |
Detailed result opens two new windows in the current project after selecting a shell model or group member, which display:
- Applied shell thicknesses (Detailed result window)
A list displays the applied thicknesses by the steel plate components. - Detailed calculation formulas (Detailed result window)
Calculation details and final values are collected by checking types: Stresses, Flexural buckling, stiff/weak direction, Torsional buckling, Lateral torsional buckling and Local buckling. The proper results are displayed in green, while the red result warnings you to repeat design with new thickness values. The content of the utilization checks depends on Display options and Buckling mode (see later). Not relevant checks can also be hidden.
Figure: Utilization checks and formulas - Summary graph (Detailed result window)
Summary graph is displayed with legend by default.
Figure: Utilization summary - Buckling mode (Buckling mode window)
Based on stability analysis, the calculated shapes of the bar-shell model can be displayed in 3D view. Just select the required shape from the Shape drop-down list of the navigator panel and the program automatically shows the deformed shape in the current display mode. Buckling mode can be also chosen for the selected shape that affects on the design check content of the Detailed result window. You can add numeric values to the deformed shape or run buckling animation.
Figure: Buckling shape
Tabmenu contains the following tools and settings for the Detailed result window:
- Selection of element to display
You can choose a unique or a design group member from the drop-down lists to display its detailed results mentioned before. Each row displays the ID and the maximum utilization of a member. In case of a design group, “Maximum” means the significant member having the maximum utilization. - Selection of design load
A load combination can be selected for detailed results. Each row displays the name of the available load combination and its utilization effect. “Maximum” means the significant load combination. Auto design
Quick Auto design can be done for the currently displayed unique/group member. Set the thickness of the steel plate components, and then click OK to start design that updates all detailed result figures and tables.Display options
The content and the appearance of the detailed result can be set with Display options.Go to
Navigate in the Detailed result window by selecting the required design type in the drop-down list. It is useful when you are in zoomed view.
Click Tools > Add view to document to place all calculation and check formulas into Documentation.