10. Connection design verifications according to Eurocode 3

A. General

The design of connections is performed using the INSTANT steel – Connections EC module which can be started from the main module INSTANT steel – Linear 3D menu by selecting Design checks > Connections EC.

The connections design implements the following checks and assumptions:

INSTANT steel incorporates the design rules of connections according to EC-3 (ENV 1993-1-1:1992 and EN1993-1-1:2005) in a steel structure.


(*) Bolts are according to reference standard 3, Annex B.

(*) Available grades for bolts are: 4.6, 4.8, 5.6, 6.8, 8.8, and 10.9

(*) The nominal values of the yield strength (fy) and the ultimate strength (fu) are to be taken from the table 6.1 below. (ΕC-3, Table 3.3).


(*) Spacing and end distances of the bolts are being verified with the limits given for the minimum and maximum allowable distances according to paragraphs §, §, §, §, §, §

(*) For pin-joined connections the design shear rupture resistance is covered according to §

(*) For truss connections with angles, the eccentricity of fasteners in end connections and the effects of the spacing and end distances of the bolts are being taken into account according to §

(*) For truss connections with angles paragraph §6.6.10 is also taken into account.

(*) For long joints factor βLf is calculated according to §6.5.10.

(*) For the welds, verifications defined in paragraphs § (1), § (1), § (2) & § are applied.

(*) Annex J is applicable on connections where the connected members are of class 1, 2, or 3 (according to cross-section classification 5.3), and they don’t require web buckling verification (chapter 5.6.1).

(*) For connections, which are verified according to Annex J, they are classified with regard of their stiffness according to §J.2.5.1 and with regard of their strength according to §J.2.5.2.

(*) Annex K is applicable on connections for which §Κ.1 & §Κ.3 are applied.

The INSTANT steel – Connections EC module allows the design of connections conforming to Eurocode either in stand-alone mode or using the results of an existing project solution created with INSTANT steel – Linear 3D. In this example the second method will be presented, since it can be obtained the section information and beam results from the existing solution.

B. Connection design procedure

We start the connection design procedure from the general window INSTANT steel – Linear 3D, by selecting: Design Checks > EC Connections as shown below.


After the completion of the above selection a new window will open called “INSTANT steel”. Select the “New” instant-wiki-08-04 icon and from the “New” dialog window that will open select “Connection project”.


This will result in opening the following dialog window called : “INSTANT steel – ConnecDoc1”. On the left hand-side there are three (3) tabs (“Project”, “Connections” and “Analysis”. Each tab initiates their own dialog window where the user maked his selections.


In the first tab, “Project”, the user defines some “Project information” as described on the next screen. For example, states the “Project name”, the responsible “Engineer”, the “Date” of the creation of the project and also the “Regulation” norm that will take place. Finally, the user also selects the “Linked job” file in order to insert the topology from “INSTANT steel – Linear 3D”.


The last selection described above, “Linked job”, will result in opening a “Select” button as shown below:


Press “Select” and a dialog window will appear where the user finds the results file that is located in the INSTANT steel 2013 > Projects > “Name of the saved INSTANT steel job”.ajf.


After, the conclusion of the above selections the “INSTANT steel – ConnectDoc1” window will load the topology and the analysis data from the specified “Projects” folder.


Now, we select the tab “Connections” and we press “Add” as shown below.


By clicking on “Add” button the different types of connections that can be examined are shown. There are 5 basic types of connections. More specifically, we have the following connections: Beam to Beam, Beam to Girder, Beam to Column, Trusses, Column Base.


For this particular example we will select to design a Beam to Column connection. By clicking on the “+” sign in front of the “Beam to Column” type, a numerous of possible connections that belong to this type will be revealed.


Select the “Moment/Bolted (end plate) one beam” connection as shown above. On the right hand-side of the screen a sketch of the specified connection will appear. By pressing the OK button the topology selected previously from the INSTANT steel – Linear 3D will load as shown below.


Then the user works on the left hand-side of the screen where gives some “Connection information” and describes the topology of the selected connection that he wishes to design according to EC3 norm. Set as “Name”, c1.


Then, select the beam members that participate in the connections, such as the column (B/C) section and the rafter (B1) section. Also, at this point the user states whether the column is continuous or not. In this example the “Upper Column” field is selected as “Not present”. Choose the steel quality of the sections that participate in the connections (S235 for both beam elements).


The selection of the section members shown above is done with the following procedure. On the left hand-side of the following window press on the B/C > Section data field. Then choose from the topology on the left hand-side the member that corresponds to the column section just by clicking on the appropriate beam element. Use the same procedure to identify the rafter section that is connected to the previously specified column from the topology on the left hand-side. As a result of the above described selections we are going to have a column section, HEA360, and a rafter section, IPE500, as shown below.


By clicking on the “Drawings View” instant-wiki-09-17 icon the screen on the right hand-side will alter as shown below. Then the user gives the following “Plate” data for the end plate of the specified connection and also some “Bolts layout” data.

Note: Any geometrical selection that the user makes in defining the connection topology, such as height of end plate, results in high lighting on the right hand-side of the screen the corresponding selection that takes place.


After finishing defining the connection topology by giving the appropriate geometrical data we have the following connection layout.


Note: The inclination of the rafter is calculated automatically from the inserted topology. In addition, the results of the loading cases are also inserted automatically.

Also, by selecting the “Solid 3D view” instant-wiki-05-33 icon the user can have a better visualization of the specified connection.


After the “Connections” topology definition is completed the user selects the third tab called “Analysis”. Then makes the appropriate “Analysis options” selections. For this example, select that “Partial safety factors” are according to “ENV(1993-1-1), the “Report language” is set to “English”, the “Display report” option is set to “Table”. Then select the created connections “c1” and select by clicking on the “Select all” option the loading cases.


After pressing “Analysis” the following text report will open.


There the user can observe the summary results of the designed connection in a Table format. As in member design the display of the results can be either in a Table or in a detailed format.

Note: Any ratio that is greater than 1.0 indicates that there is a failure in the design of the particular connections and changes in the connection topology definition should take place.