Did you know that you could use Consteel to calculate effective cross-section properties for Class 4 sections?

The classification of cross-sections is used to understand how local buckling affects the strength and rotation capacity of structural members. As stated in Eurocode 3 (EN 1993-3-3, Section 5.5), this classification helps determine whether a cross-section can reach its full resistance or if its behavior is limited by local instability.

Class 4 cross-sections are those in which local buckling occurs before the material reaches the yield stress in one or more parts. Because of this, their resistance must be calculated using effective section properties that take into account the reduction caused by local buckling.

Typical Class 4 sections are characterized by slender elements with high width-to-thickness ratios. These commonly include thin webs or flanges, hollow sections (RHS/CHS) with slender walls, thin-walled cold-formed profiles such as C- or L-sections, and welded I-sections with slender webs. In this example, we consider a welded I-section with the following geometric parameters:

In Consteel, we can then see the section classification from the Global Checks tab. After selecting the investigated section either in the model or from the table and clicking on the Calculate Section option, and then choosing the Plate Classes in the Properties tab.

The effective section properties can then be viewed using the second option in the Properties tab.

In addition, stresses can be visualized by clicking on the Stresses icon. They can be represented either as a colored figure or as a 3D diagram.

For Class 4 sections, the Standard Resistance tab in the section module provides a complete assessment for the selected loading case.

The section module performs all necessary calculations according to the Eurocode (EN 1993-1-1 and relevant parts of EN 1993-1-5), including general elastic resistance, pure case resistance, conservative interaction checks, and web buckling analysis.

All resistances are calculated using the effective section properties to account for local buckling, and the module identifies the dominant case to ensure all relevant checks are covered.

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Did you know that you could use Consteel to Consider the shear stiffness of a steel deck as stabilization for steel members?

In many practical steel structures, trapezoidal decking is treated only as a load-bearing surface. In reality, when properly connected to the supporting members, it behaves as a shear diaphragm and contributes to the overall stability of the structure. This effect can be directly taken into account in Consteel by applying shear field stiffness to beam elements.

The stabilizing effect comes from the in-plane shear stiffness of the deck. Under horizontal loading, the sheeting deforms and transfers forces between structural members. This behavior can be described by a single parameter, the shear stiffness (S), which represents the resistance of the diaphragm against deformation.

The overall stiffness is influenced by several components, including the shear deformation of the sheet, profile geometry, fastener slip, and connection flexibility. These contributions together define how effectively the deck can restrain phenomena such as lateral-torsional buckling.

A key requirement for this behavior is proper fastening. Typically, the sheeting must be connected along its edges and fixed to supporting members at each rib to ensure reliable diaphragm action.

In engineering practice, shear stiffness is determined using standardized or manufacturer-based methods rather than detailed analytical models. Consteel supports several established approaches:

• Schardt/Strehl method (DIN 18807), based on parameters describing shear and warping deformation
• Improved Schardt/Strehl method, including the effect of fastener spacing
• Bryan/Davies method, considering additional structural parameters
• Eurocode-based method, using general geometric properties of the sheeting

These methods differ in complexity and required input data, but all aim to provide a realistic stiffness value for use in global analysis. If the sheeting is not fixed at every rib, the calculated stiffness must be reduced accordingly.

The shear field object in Consteel allows engineers to include the diaphragm effect without detailed shell modeling. The calculated shear stiffness can be assigned directly to beam elements, providing additional lateral restraint.

The process involves selecting a trapezoidal sheet profile, choosing the appropriate calculation method, and defining the relevant geometric and connection parameters. The software then determines the stiffness and incorporates it into the structural model.

Including shear stiffness in the analysis can lead to higher critical load factors and reduced displacements, resulting in more efficient structural designs. However, it also means that the decking becomes part of the stabilizing system.

Any later modifications to the sheeting, such as openings or changes in fastening, may reduce this effect and should therefore be carefully assessed.

The shear stiffness of trapezoidal steel decking provides a measurable and often significant contribution to structural stability. By incorporating this effect in Consteel, engineers can achieve more realistic analysis results and optimize their designs while maintaining structural safety.

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Did you know that you could use Consteel to draw a user-defined cross section and calculate its section properties?

In our previous article, we showed how predefined macro geometries make modelling fast and efficient. Later, we demonstrated how Consteel evaluates local and distortional buckling according to EN 1993-1-3.

This article focuses on the most flexible solution within this workflow: creating your own cross-section from scratch using the Section drafter module.

For line member modelling, the cross-section must first be loaded into the model. Besides using standard library profiles or macro sections, you can also choose the Draw Section option. This function is especially useful when a special geometry is required that cannot be reproduced with predefined macros, for example manufacturer-specific shapes, research sections, welded thin-walled members, or prototype geometries.

The Section drafter can be started from the Section Administration dialog by pressing the Draw section button. After launching the function, you need to select the section type, material quality and assign a name.

Two types of cross-sections are available: Cold formed section and General thin-walled section. This selection is not only geometric but also analytical.

Cold-formed sections are drawn with a single reference line and uniform thickness. During the calculation, Consteel automatically considers distortional buckling effects according to EN 1993-1-3. These sections can later be used in purlin line objects if they are defined as Z- or C-like shapes.

General thin-walled sections allow different thicknesses along the contour and closed geometries. They are typically used for welded or fabricated sheet sections. In this case, strength, local and global stability checks are available, but distortional buckling evaluation is not included.

The drawing environment provides full control over geometry. Plate segments can be defined by coordinate input or by graphical selection. Cartesian or polar coordinates can be used, in local or global systems. Roundings are generated automatically between segments and can be modified later. The nominal thickness is also specified at this stage.

For cold-formed sections, stiffeners can be inserted using predefined macros, making it easier to model edge or intermediate stiffeners. However, these become structurally effective only after they are properly defined in the final phase of the section creation process.

Once the geometry is complete, the required design parameters must be specified. For cold-formed sections, this includes the manufacturing type, thickness tolerance category and buckling curves. These inputs influence the calculated design wall thickness and stability verification. In the next step, the program evaluates the classification of each plate segment and determines the effective widths used in resistance calculations.

If stiffeners are present, they must be defined explicitly. When the section is identified as Z- or C-like, Consteel can automatically determine the critical stress of the stiffeners in accordance with EN 1993-1-3. This ensures that distortional buckling and stiffener interaction are properly considered during design.

After saving the section, it can be assigned to line members just like any library or macro profile. Following structural analysis, steel design checks can be performed. As shown in our article on buckling checks, the Section module allows detailed review of effective cross-sectional properties, reduction factors, slenderness values and stiffener behaviour. Consteel automatically accounts for distortional buckling when the supplementary rules of EN 1993-1-3 are enabled.

By combining library, macro, and user-defined sections, Consteel provides a complete workflow: fast modelling with macros, precise verification through buckling checks, and full flexibility with custom cross-sections.

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Did you know that you could use Consteel to include in your model a wide range of cold-formed macro sections?

For line member modelling, the cross-section must first be loaded into the model. In Consteel, there are four options to do this, either starting from the Section Administrator or directly during beam or column modelling: From Library, Macro Section, Draw Section, or My Library.

Cold-formed sections can be created using any of these four methods. Standard cold-formed cross-sections can simply be selected from the library. However, if a special cold-formed section is needed, it can be created via Macro Sections, including: RHS, CHS, L profile, Z shape, C shape, Sigma section, Zeta section, Hat section with stiffeners, double C section, double Sigma section, and double user-defined sections.

Macro sections are easy to create because the essential geometric characteristics are predefined, and the parameters can be modified intuitively. It is also possible to add profile stiffeners. Flange and web stiffeners can be configured in various forms, including single and double options. These defined stiffeners are included in the structural evaluation of distortional buckling, according to EN 1993-1-3.

The thickness tolerance category must be specified. This determines the design wall thickness for the section. In practice, macros follow the commonly applied tolerance categories used for coated steel sheet products.

If you want to use a double section, make sure to load into the model first the section that you want to duplicate.

For very special or unique sections, the Draw Section function can be used. This allows users to create fully custom cross-sections when standard or macro shapes are insufficient, by manually sketching the geometry.

Sections can be defined as cold-formed or general thin-walled, which determines how they are analyzed: cold-formed sections have uniform thickness and account for distortional buckling, while general thin-walled sections allow varied thicknesses and closed shapes, typically for welded or fabricated profiles.

This approach is especially useful for modelling unique shapes, prototypes, or as-built sections, giving full control over every segment to accurately capture geometries that standard libraries or macros cannot reproduce.

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Did you know that you could use Consteel to perform structural analysis at room and elevated temperatures as part of design process for fire resistance?

In structural fire engineering, the mechanical response of steel structures must be evaluated under both room and elevated temperature conditions. Consteel permits this by incorporating temperature-dependent material behavior directly into the finite element analysis, allowing engineers to assess not only resistance but also changes in global structural response.

During fire analysis, Consteel determines the steel temperature and applies the corresponding reduction in material properties, most notably the modulus of elasticity and yield strength. These reductions are defined according to Eurocode 3 (EN 1993-1-2). As a result, the calculated internal forces and deformations reflect both the applied loads and the effects of thermal expansion and stiffness degradation. The analysis is performed on the global structural model, so compatibility effects and force redistribution are inherently captured.

Fire exposure is defined using nominal fire curves (Standard, External, Hydrocarbon), together with a specified fire resistance time. In addition, the model allows assignment of fire protection conditions, including unprotected members, hot-dip galvanized surfaces, and protected elements with either passive insulation or reactive (intumescent) coatings. These definitions influence the temperature development in the structural members and, consequently, their mechanical response.

For design verification, Consteel applies the resistance models of EN 1993-1-2. Cross-section resistance is calculated using temperature reduction factors​, depending on the type of internal force and cross-section class. Checks are performed for tension, compression, bending, and shear, as well as their interaction. For global stability, the software uses the Eurocode general method with modified buckling curves and reduction factors adapted for elevated temperatures.

In addition to elevated-temperature analysis, Consteel supports a complementary approach based on room-temperature analysis for critical temperature determination. In this case, the structural analysis is carried out with ambient material properties, and the objective is to find the temperature at which the reduced resistance equals the internal forces from the governing load combination. This method is particularly relevant for members with intumescent coatings, where the coating performance depends on the critical steel temperature. The calculated critical temperature can then be used to determine the required coating thickness based on product-specific data.

The difference between these two approaches can be illustrated using a two-storey frame model.

In the first case, the analysis is performed at room temperature. The beams develop a bending moment of approximately –59.55 kNm, while the columns carry primarily axial forces and show no significant bending moment along their length. This is consistent with the expected behavior based on the initial stiffness distribution of the structure.

In the second case, the analysis is performed at elevated temperature, where reduced stiffness and thermal expansion are taken into account. The beam moment remains –59.99 kNm, but the internal force distribution in the structure changes. Bending moments appear in the columns, reaching approximately –26.91 kNm and –42.21 kNm at midspan.

This difference is a direct consequence of two coupled effects. First, the reduction in modulus of elasticity decreases the stiffness of heated members, modifying the relative stiffness distribution within the frame. Second, thermal expansion introduces additional deformations, which are partially restrained by the structural system. In statically indeterminate structures, such restraint generates additional internal forces, leading to redistribution of moments and the appearance of bending in members that were previously dominated by axial force.

From an engineering perspective, this comparison highlights that the internal force system under fire conditions is not a simple scaled version of the ambient-temperature state. Instead, it is the result of a different equilibrium condition, influenced by temperature-dependent material behavior and compatibility effects.

By allowing both types of analysis within the same model, Consteel provides a consistent framework to evaluate these phenomena. This supports more accurate assessment of structural performance in fire and enables informed decisions regarding fire protection and member design.

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Did you know that you could use Consteel to calculate the elastic critical moment of a member subject to arbitrary loading and boundary conditions?

Calculating the elastic critical moment can quickly become difficult when beams have tapering, unusual restraints, or complex loads. Consteel simplifies the process and gives a quick, accurate result for any situation.

The elastic critical moment for lateral-torsional buckling is the theoretical bending moment at which a beam, free to sway sideways and twist, becomes unstable and buckles elastically, before yielding, representing the absolute upper limit of elastic stability for beam bending. It depends on: cross-section stiffness properties (I_z, I_w), material (E, G), span / buckling length, restraint to lateral displacement and to warping at the restraints, and on the shape of the moment diagram (via factors C₁, C₂, C₃).

For doubly symmetric I- or H-sections with constant cross-section, uniform bending, and classical boundary conditions, the elastic critical moment M_cr can be calculated using the analytical formula:

However, for arbitrary support conditions and loading scenarios, the calculation becomes significantly more complex, and the classical formula is no longer applicable. In such cases, specialized software such as LTBeam or Consteel is required.

Let’s consider a tapered, welded I-section with pinned supports at both ends and two intermediate restraints, one at the bottom flange and one at the top flange. In addition to the uniform distributed load, a bending moment is applied at one end of the beam.

By performing a buckling analysis in the Analysis tab, the buckling shapes and the critical load factor (αcr​) can be obtained. The elastic critical bending moment of the beam can be then calculated by multiplying the critical load factor by the maximum bending moment.

Consteel uses seven-degree-of-freedom finite element that fully accounts for tapering effects, torsion, and warping, key components in accurately capturing the true 3D behaviour of steel members. The seventh degree of freedom represents cross-sectional warping, which becomes visible in the buckling shape as the flanges move out of the plane of the cross-section.

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Did you know that you could use Consteel to design simple supported, continuous and over-lapped purlins systems, considering shear and rotational stiffness of attached roof sheeting?

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Did you know that you could use Consteel to determine the critical temperature of a steel beam protected against fire with intumescent painting?

For critical temperature determination, the analysis must be set to room temperature material properties, because the objective is to find the exact temperature at which the steel section can no longer resist the applied loads while the intumescent coating reacts.

The key step is to assign reactive fire protection to the beam. This activates Consteel’s intumescent coating model, which calculates the temperature at which the reduced cross-section resistance equals the internal forces from the applied load combination. The software accounts for tension, compression, bending, and combined loading using Eurocode reduction factors, including interaction checks for complex load scenarios.

After completing the fire design, you can also include an intumescent paint design in the documentation. This report can list each cross-section selected for painting, along with the section name, fire protection surface to be painted, A/V ratio, and the critical temperature for each member.

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Did you know that you could use Consteel to design a hot-rolled crane beam considering the effect of code-prescribed load eccentricities?

Designing crane beams often involves more than simply applying vertical loads. Code-prescribed eccentricities, arising from rail positioning, wheel load distribution, and horizontal forces, can significantly influence internal forces and stability checks.

In Consteel, you can define three types of overhead traveling crane loads. The Standard option is fully based on EN 1991-3, following the code provisions directly. With Standard load based, you specify the standard-defined wheel loads, and Consteel automatically creates the corresponding load groups for you. The User defined option gives you full control, letting you input the wheel loads individually for each wheel, which is useful if your crane has a non-standard configuration.

Once you select the type of crane load, you set the crane’s geometry, loading, and driving properties according to the chosen method. This includes parameters such as the crane span, trolley distances, number of axes, self-weight of the bridge and trolley, elevated load, number of driven wheels, drive system, friction factor, and guiding device.

For Standard and Standard load based options, Consteel calculates the wheel loads automatically and generates the load groups, while the User defined option lets you input each wheel load manually. The calculated wheel loads can be reviewed for each load case, helping you ensure that the crane beam design reflects the actual forces according to the selected standard or custom configuration.

A key aspect of this method is that the eccentricity of the wheel loads is included directly in the analysis. This means that the internal forces along the beam account for the positioning and distribution of the loads.

By carefully defining the crane geometry, load magnitudes, and driving properties, the resulting bending moments and shear forces correspond closely to the real crane configuration, allowing for a reliable assessment of the hot-rolled crane beam under the prescribed loads.

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Consteel offers a range of load combination filtering options, which can be applied based on limit states, load cases, and analysis and design results. By applying different series of filters, designers can streamline their workflow and reduce calculation time.

Filtering options

Filtering is realized through the Load combination set definition window.

Filtering by limit states and by load cases are handled together with the checkboxes under the Limit states and Load cases buttons.

The 3-state checkboxes affect each other as they are not only used for selection but also for indication of the content. They can be manually set only to checked or unchecked. The middle state only appears when other filters are applied.

Filtering by limit states or load cases does not require any calculation results.

Filter by rules, on the other hand,is based on the actual analysis and/or design results. Different types of rules can be applied one by one or at the same time to select the desired load combinations.

When a rule is applied, all the load combinations that are selected on the Load combination set definition dialog- either with filtering by limit states/load cases or checked in manually- are examined at every position the rule indicates. Load combinations that meet the rule’s criteria are selected (remain checked in), while those that do not, become unchecked.

• With analysis rules, load combinations can be selected based on deformations or internal forces at either every finite element node or only at the member ends. This last one is included specifically for connection design. Deformations are checked in SLS combinations, internal forces are checked in ULS combinations only.
• With buckling rules, those ULS load combinations can be selected which have the elastic critical load factor (first buckling eigenvalue) less than the given limit.
• With design rules, load combinations can be selected based on utility ratios checked in every finite element node of the chosen portion. Utilizations are available from several design checks: dominant results and detailed verifications for steel elements such as general elastic cross-section check, pure resistances, interactions and global stability. Only ULS combinations can be filtered with design rules.

Interaction of the different filter types

Let’s see an example.

It is a simple 2D frame model, with 27 load combinations of various limit states generated. Analysis and design results are calculated for all load combinations.

If applying design rule to select only those load combinations which result dominant utilization over 50%,

4 load combinations will be selected (Load combination set 1):

But if ULS Accidental limit state is turned off before applying the same 50% filter,  

only one load combination is selected (see Load combination set 2).

Application of multiple rules

Applying multiple rules together results in the sum of the lists that would have been created separately.

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