Did you know that bar members can be included in load distribution even when slightly offset from the surface, by using a Load Transfer Surface with a user-defined tolerance?
A Load transfer surface (LTS) is a special type of surface that converts surface loads into line loads and distributes them to structural members. This is particularly useful when surface loads, such as floor loads, snow loads, or wind loads, need to be transferred to supporting members.
In order to use the meteorological load generator function or our fluid-dynamics-based universal wind load generation tool, FALCON, the load transfer surfaces (LTS) on the structure must intersect, they must meet along a common edge. Otherwise, the results will not be accurate.
This creates a problem when, for example, the purlins take over the meteorological loads from the sheets or panels, but their planes do not intersect. In this case, the LTS is applied to the plane of the main structure, while the members assigned to it may lie within a specified distance from that plane.
To define the tolerance for the load transfer surface, first go to the Options menu. There, you can set the maximum allowable distance between the bar members and the load transfer surface. In this example, all members that are less than 1000 mm from the surface can be assigned to the load transfer surface.
In order to be able to manually select the members attached to the load transfer surface, when defining it, make sure that in the Select members section you choose the Distribute load to the selected members option. If this option was not selected initially, you can set it later by selecting the surface and defining the member selection in the Object Properties window.
In the example model below, observe how the load distribution changes from the main beams (left side) to the tops of the purlins (right side) by introducing a user-defined tolerance and assigning the appropriate members to receive the load from the roof.
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Try Consteel for freeConsteel recommends to use the General Method from EN 1993-1-1 for the evaluation of out-of-plane strength of members and sturctures. In addition, the scaled imperfection based 2nd order approach is available.
Did you know, that when linear buckling eigenform affine imperfections are used, Consteel can scale automatically the selected eigenmodes to perform a Eurocode compatible design? And you can even combine several imperfections?
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Bending:
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Have you ever heard about the ‘General Method’? This is an alternative design method to consider the interaction of axial compression with major-axis bending for general buckling situations, where the main interaction formulas are not applicable.
This basically includes every member with monosymmetric or asymmetric cross-sections or with cross-sections not uniform along the length (welded tapered sections) or laterally stabilized by sheeting or anything else without providing full fork supports.
Did you know, that the General Method is fully supported by Consteel and provides an automated buckling verification possibility? Of course, for the use of the General Method in a general case the traditional 12DOF beam finite elements are not applicable. But the special 14DOF beam elements used by Consteel are perfectly compatible?
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Did you know that you can use Consteel to design a pre-engineered Metal Building with all its unique characteristics, including web-tapered welded members, the interaction of primary and secondary structural elements, flange braces, shear and rotational stabilization effect provided by wall and roof sheeting?
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Did you know that in addition the standard Type 1 and Type 2 response spectrums defined by Eurocode 8, you can use also user-defined spectrums with Consteel?
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Did you know that you can use Consteel to design simple supported, continuous and over-lapped purlins systems in Consteel, considering shear and rotational stiffness of attached roof sheeting?
To use the purlin design functions, you first need to place cold formed Z or C purlins in your model, these are the only profile types supported for purlin design. All functions related to purlin lines can be found in the Structural members tab.
With these three main functions you can define the purlin line object, specify the support zones, and set the overlap zones. A detailed explanation of each can be found in the Consteel Manual – Purlins Chapter.
The Place purlin line function allows you to create and configure a purlin line object and place it precisely within your structural model.
You can also control the sheeting eccentricity in the Z direction, either by selecting predefined positions or by entering custom values. A graphical interface supports these settings to ensure intuitive and accurate placement.
An important feature of this function is the ability to simulate the supporting effect of roof sheeting on the purlins. This is done by applying spring stiffnesses that reflect how the sheeting contributes to the overall structural behavior. Two types of springs are considered:
- Translational (shear) spring, representing the shear stiffness of the roof covering.
- Rotational spring, accounting for both the connection stiffness and profile distortion.
Depending on the selected sheeting type (trapezoidal sheeting or sandwich panels) the stiffness values can be entered manually or calculated automatically. Automatic calculations follow the guidelines of EN 1993-1-3, providing reliable and standards-based results.
The Support zone function allows you to define the geometrical and mechanical parameters at the points where the purlins are supported. The geometry and bearing capacity can be set by specifying the support width and selecting how the load capacity is defined.
The Purlin overlap function helps define how individual purlins are connected in continuity. The standard (EN 1993-1-3) distinguishes between simple overlap joints and joints with coupling elements. Currently, only overlap joint is available in the program. You can define the length of the overlap either in millimeters or as a percentage of the member length. Additionally, the stiffness distribution between the two overlapping members can be adjusted.
Together, these functions ensure accurate modeling of purlin behavior, support conditions, and connection details, aligning with design standards and practical requirements.
To ensure that all purlin line related objects are properly considered in the analysis, make sure to activate the Cold formed purlin design mode in the analysis settings. When this mode is enabled, both the buckling analysis and the global design are performed on a submodel that includes only those members associated with purlin line objects. This mode is intended exclusively for the design of the roof purlin system.
If purlin related objects are present in the model but the cold formed purlin design mode is not active, the structural elements connected to these objects will be excluded from the second-order stiffness matrix. As a result, their influence will not be considered during linear buckling or second-order analysis.
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Try Consteel for freeDid you know that you can use Consteel to design pad foundations?
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Did you know that you can use Consteel to calculate support settlement?
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Did you know that you can use Consteel to apply your own scripts to build models and perform calculations?
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Did you know that you could use Consteel to build 3D models with smart link elements which automatically adapt the model when profiles are changed?
Link elements are used to connect members that are not directly joined. In Consteel, three types of link elements are available: Link, Smart Link, and Constraints.
A smart link is a dynamic connection element designed to simplify the management of geometric changes between connected members. It automatically follows the movement, rotation, or profile changes of the primary member it is attached to, while also ensuring that any connected secondary member adapts accordingly.
A common application is connecting a main beam to a purlin or other secondary elements, with smart links positioned at specific points. They enable easy attachment of additional members while preserving the defined eccentricity, and automatically adapt to any changes in the main beam’s geometry or profile.
The Smart Link function, located on the Structural Members tab, opens the Edit Smart Link dialog box after activating the command. This allows you to:
- define the eccentricity of the link relative to the main section
- set the connection type in the Release field
The connection position can be specified manually or left to default automatically to the edge of the main member.
Defining the connecting section is optional. When specified, an eccentricity can be assigned, and the program automatically determines the link length based on the section height and reference point.
Smart links can be placed individually by clicking on a member or in groups by specifying distances from the member’s start. Any placement conflicts are indicated by a warning.
By combining associative behavior with precise control, Smart Links support efficient and reliable 3D modeling in Consteel. They help maintain structural intent throughout design changes, reduce manual corrections, and improve overall model consistency.
For workflows where geometry evolves and secondary members must remain accurately connected, Smart Links provide a clear advantage and enable a more resilient and adaptable modeling process.
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