Steel connection design extensions in SCIA Engineer 16.1
Version 16.1 brings both new developments and various improvements in the module for steel connection design Rigid frame connections (esasd.02). The developments described below demonstrate again that integrating 3D structural analysis and member-based checking and connection verifications in one interface provides transparency of the design workflow and contributes to a high quality of analysis, results and outputs.
EC3 support and beyond
The following developments from version 16.1 are the most prominent in the field of steel connection design:
- The implementation of base plate design in SCIA Engineer has been completely revised in order:
- to support additional reinforcing elements in a base plate connection, namely, the presence of symmetric and asymmetric haunches;
- to perform the design calculations in full accordance with the latest version of EN 1993-1-8 (2005).
- Based on a recent publication, the calculation method for connections with 4 bolts per row has been extended with a group approach for the determination of tensile resistance of bolt-rows.
- The evaluation of girder resistance at the beginning of a haunch has been integrated in the component-based approach, bringing more clarity to the calculation report on, e.g., which components of the connection are limiting and where the user should improve in order for the connection to provide sufficient resistance.
- All our bolt assembly libraries have been updated according to the latest ISO and EN codes for bolts, screws, nuts and washers.
In parallel to the Eurocode, we consulted additional publications for design situations not directly described in EN 1993-1-8:2005. These papers build upon the component method for steel connection verification and elaborate on some specific cases. References are listed further in the relevant chapters of this text.
These newly added extensions fit within SCIA's history of practical implementations of Eurocode design expertise inside the Computer-Aided Engineering (CAE) platform SCIA Engineer. They demonstrate that our development team's knowledge of steel connection design stretches beyond sheer knowledge of the Eurocode itself: we correctly interpret and implement the design principles described in EN 1993 and in other related publications that broaden the scope of the component method.
Improved user experience
Developments in steel connections from version 16.1 complement what was added in version 16.0, namely:
- the support for weak-axis bending of strong axis beam-to-column connections: i.e., combined bending and multi-planar shear (My + Mz + Vz + Vy) in a moment-rigid connection;
- the design based on the component method for beam-to-column connections with 4 bolts per row;
- the complete automation of the Update stiffness function in SCIA Engineer; in other words, the ability to automatically obtain flexible and nonlinear springs in steel joints in both linear and nonlinear analysis, respectively;
- an improved calculation report.
Recent developments in versions 16.0 and 16.1 further develop the concept of integrating connection design directly in the 3D modelling interface. This includes taking joint stiffness into account in 3D analysis, even in the case of weak-axis bending of strong-axis connections.
We can say that the module Rigid frame connections is a powerful tool for steel frame design, as it not only determines the connection capacity and rotational stiffness:
- it points out the prevailing failure modes;
- it classifies the connection based on stiffness and notifies the user if assumptions in the analysis model are not valid;
- it derives the moment-rotation characteristics of the joint and it takes the joint flexibility's influence on the whole analysis model of the structure;
- it provides a clear calculation report with references to the relevant chapters of the code.
Base plate design
SCIA Engineer's module for design of moment-rigid connections (esasd.02) is now completely reprogrammed in order to provide better computational performance. But this is not the only benefit. Improvements can be seen in the scope of supported geometries, in the used calculation methods, and in the outputted documentation.
Base plate connections can now use stiffening elements that were previously available in SCIA Engineer only in beam-to-column joints. The user can introduce single or double-sided haunches and verify the connection capacity and stiffness taking these into account.
The presence of haunches has influence on the relevant components and failure modes of the base plate connection. By combining haunches with column flange extensions, the user can increase the connection capacity and stiffness in both the major and minor direction of the column base.
Haunches can also be introduced to inclined columns; in those cases, the base plate can be either perpendicular to the column or horizontal in relation to the global coordinate system.
Transparent calculation according to EN 1993-1-8
The three major stepping stones of base-plate design have been rewritten in full accordance with EN 1993-1-8:2005:
- the calculation of moment resistance in the presence of axial force is now calculated as specified in §18.104.22.168 (with references to §22.214.171.124, §126.96.36.199, §188.8.131.52, §184.108.40.206, and §220.127.116.11);
- in the case when no bending moments are present in the joint, axial force resistance is calculated as specified in §18.104.22.168;
- the determination of rotational stiffness is calculated as specified in §6.3.4;
- the classification of the connection is performed based the actual rotational stiffness and the limits specified in §22.214.171.124(2).
These calculations take into account the relevant components in the connection and the internal forces that are present in the support. The user specifies which load combination or Result Class will be used for the connection verification. The set of critical internal forces is used in the determination of prevailing stress pattern under the base plate: full compression, full tension, compression on one side and tension on the other.
Anchor length according to EN 1992
The length of anchor bolts is now determined according to §8.4 of EN 1992-1-1; the calculation takes into account the bond strength of the used concrete class and the specified bond conditions (good or poor). Stress in the anchor bolts is calculated either from the internal forces that are present in the support or from the highest bolt-row resistance obtained in the calculation of Mj,Rd.
Minimal anchorage length requirements according to §8.4 are also taken into account.
In the case when the foundation dimensions underneath the base plate are already known, these can be defined in SCIA Engineer. This will allow for the strengthening effect of the concrete block around the zone in contact with the base plate to be taken into account in the compression strength of the grout layer under the base plate-- i.e., the design bearing strength of the grout will be increased in the calculation of the T-stud in compression.
The assumptions of the calculation method employed here are described in the dissertation: "Steel column bases under biaxial loading conditions," P. M. Amaral, 2014.
The user will also find that the calculation report has improved:
- The layout of the report now follows more closely the structure of the EuroCode;
- Intermediate calculation steps allow the user to benchmark to hand calculations;
- The user will find consistently added references to articles from the code in all chapters of the report.
Connections with 4 bolts per row
A modern method for the verification of steel connections with 4 bolts per row was implemented in SCIA Engineer version 16.0. This method has now been extended with a group approach for the determination of the tension resistance of bolt rows.
The group approach for connections with 4 bolts per row in explained in the publication "Recommandations CNC2M pour le dimensionnement des assemblages selon la NF EN 1993-1-8" (2015), which extends the previously implemented method from "Applications of EuroCode 3 to Steel Connections with Four Bolts per Row," J.-F. Demonceau, K. Weynand, J.-P. Jaspart and C. Müller, 2011.
By taking into account the limiting combined resistance of bolt-row groups in the framework of the component method, SCIA Engineer is capable to capture more complex failure mechanisms, e.g., yielding that spreads over multiple bolt rows, punching of a large segment of the end plate in the tension zone.
Based on the publication mentioned above, other extensions to the original method were made. These can be summarised as follows:
- The presence of 4 bolts per row can now be taken into account for all bolt-rows located in the tension zone (previously this was only possible for bolts adjacent to flanges or stiffeners;
- No distinction is made based on the presence or not of prying forces in the case of Mode 1 & 2 failure;
- The shear resistance of all bolts that are used for tension is modified to take into account the combination of forces.
The described extensions are implemented in both base plate connections, end-plate beam-to-column connections, and splice beam-to-beam connections.
Haunched member resistance
In the case of connections with a haunch, the resistance of the connected member at the haunch end also needs to be verified according to the component method.
In SCIA Engineer version 16.1, this is now done in a clear way which fully complies with the requirements of EN 1993-1-8, i.e., two new components have been added to cover the failure mode at the location in question:
- haunch flange in compression
- beam (or other connected member) web in compression (which is calculated similarly to the standard component column web in compression).
The calculation report now clearly indicates the resistance of these components and makes it clear to the user if failure occurs there and if stiffening needs to be added.
The method is elaborated in the publication "Eurocode 3: Bemessung und Konstruktion von Stahlbauten, Band 2: Anschlüsse – DIN EN 1993-1-8 mit Nationalem Anhang – Kommentar und Beispiele," Prof. Dr.-Ing. Dieter Ungermann, Prof. Dr.-Ing. Thomas Ummenhofer, Prof. Dr.-Ing. Ramgopal Puthli, Dr.-Ing. Klaus Weynand, 2015.
Updated bolt libraries
SCIA Engineer's bolt libraries have been updated and now comply with the latest ISO/EN codes for bolts, screws, nuts and washers.
The following codes are now supported in the Bolt Assembly library of SCIA Engineer:
- for normal bolts:
- EN ISO 4014:2011 (updated)
- EN ISO 4016:2011 (updated)
- EN ISO 4017:2011 (updated)
- EN ISO 4018:2011 (new)
- EN ISO 4032:2000 (new)
- EN ISO 4034:2000 (new)
- EN ISO 7089:2000 (new)
- EN ISO 7090:2000 (new)
- EN ISO 7091:2000 (new)
- for preloaded bolts :
- EN 14399-3:2005 (new)
- EN 14399-4:2005 (new)
- EN 14399-5:2005 (new)
- EN 14399-6:2005 (new)