When defining steel connections, it is often necessary to incorporate stiffening elements such as longitudinal ribs. The new versions of RFEM 6 (starting from 05.0006) allow you to do this in a fast and user-friendly manner. Compared to the previous versions, which did not contain the “Rib” as an individual component, the procedure is significantly simpler and more straightforward. This text will show you both procedures so you can get to know the advantages of the “Rib” component and its use. For this purpose, the connection shown in Image 01 will be modeled first without using the rib component, and then the same will be done using the aforementioned option.
The connection to be modeled is shown in Image 01. The next image, Image 02, shows the members it connects. If you have already created steel connections using the Steel Joints add-on, you are probably familiar with the fact that as soon as you assign a design node (node No. 53 in this model), the program assigns all the members connected to the node. For the joint in question, 5 members in the model need to be referenced: member No. 40 (Column 1), member No. 41 (Beam 1), member No. 42 (Column 2), member No. 43 (Beam 3-1), and member No. 44 (Beam 3-2), all displayed in Image 02.
Now, let’s analyze which components (except the rib) can be used to model the connection in the Steel Joints add-on. First, Beam 1 needs to be connected to the column. Since two elements (the beam and the column) are to be connected by means of a bolt group, end plate, and welds, you can use the “End Plate” component offered in the add-on, where Beam 1 is the connected member and the column is the reference element. Next, the connection should be reinforced with haunches. A “Haunch” component in the Steel Joints add-on consists of a single extending plate or an extending plate supplemented (optionally) by a flange. As Image 03 shows, three haunches are added to the component list for the connection in question as extensions of the web of Beam 1. Then, to create the pinned connection, the “Fin Plate” (one on each side) can be used as a component which connects a member to a reference member using a bolt group and a connecting plate. Finally, you can use the “Cleat” component to connect Beam 3-1 to the columns. The reference members in this case are the columns (Columns 1 and 2), while the connected member is Beam 3-1.
All the above-mentioned components are shown in Image 03.
Now that the other components have been inserted into the program and their settings properly defined, let's take a quick look at the rib modeling prior to version 05.0006. First, you need to insert not one, but two plates (Plates 1 and 2 in Image 04) to have the rib on both sides of the beam. Then, you need to insert four plate cuts: two for the cut across the end plate and Plates 1 and 2, respectively, and two for their cut across Beam 1 (one for each of the plates). In addition, a Plate Editor should be inserted for both plates (Plate Editors 1 and 2 in Image 04) to adjust the plate corners by chamfering them. This way, you must insert 8 separate components and define their settings to model the rib (Image 04).
Our mission at Dlubal is to constantly improve our programs and provide you with the best tools for easy, straightforward, and time-saving modeling, analysis, and design. Hence, starting with version 05.0006, you no longer need to perform all the steps mentioned above. Instead, you can simply add the "Rib" component, which you can find under "Stiffening Elements", as shown in Image 05.
Once inserted, defining the settings of the components is easy and fast. As Image 06 shows, first you need to define the object to be stiffened (in this case, the web of Beam 1) and the reference object (in this case, End Plate 1). Then, you can adjust the position of the rib with respect to the side (front, rear, or both) and the number of ribs and/or the distance between them. This allows you to define any number of longitudinal ribs on a member plate in just one step. Next, you can define the settings for the plate, such as material, thickness, orientation, dimensions, stiffened member indent, and reference indent. Finally, you can customize the type and dimensions of the welds in relation to the stiffened element and the reference object and choose between front or back fillet weld, front or back weld, and double fillet weld.
Final Words
The Rib component is a new feature that greatly facilitates the modeling of stiffened steel connections and makes the process of incorporating stiffening elements faster and more user-friendly. You only need to select the stiffened and reference objects and specify rib position, shape, and welding options. Furthermore, you can define any number of longitudinal ribs on a member plate in just one step. This significantly reduces the number of components used in the states before and after the implementation of this feature and makes modeling of stiffened steel connections uncomplicated, quick, and straightforward.
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