The "Results by Story" table of a building model shows the center of gravity for load cases and load combinations. In addition to the self-weight, the vertical loads of the respective load cases and load combinations are also taken into account.
You can also use the "Center of Gravity and Information About Selected Objects" dialog box to display the center of gravity, taking into account the selected loading.
When modeling stories, you can use the "Semi-Rigid Diaphragm" option for slabs.
In principle, this modeling option selects the same approach as for the "Rigid Diaphragm" modeling of stories. In contrast to the rigid diaphragm, no nodal coupling is carried out from the center of gravity to each FE node. This way, it is possible to take into account the flexibility of the slab.
You can neglect openings with a certain area in the building model calculation. This function can be activated in the global settings of the building stories. A warning message appears saying that the openings have been neglected.
Global 3D calculation of the global model, where the slabs are modeled as a rigid plane (diaphragm) or as a bending plate
Local 2D calculation of the individual floors
After the calculation, the results of the columns and walls from the 3D calculation and the results of the slabs from the 2D calculation are combined in a single model. This means that there is no need to switch between the 3D model and the individual 2D models of the slabs. The user only works with one model, saves valuable time, and avoids possible errors in the manual data exchange between the 3D model and the individual 2D ceiling models.
The vertical surfaces in the model can be divided into shear walls and opening lintels. The program automatically generates internal result members from these wall objects, so they can be designed as members according to any standard in the Concrete Design add-on.
Shear walls and deep beams of a building model are available as independent objects in the design add-ons. This allows for faster filtering of the objects in results, as well as better documentation in the printout report.
The building story generator in the Building Model add-on provides you with the option to automatically create building stories, depending on the topology of the model.
The modal relevance factor (MRF) can help you to assess to which extent specific elements participate in a specific mode shape. The calculation is based on the relative elastic deformation energy of each individual member.
The MRF can be used to distinguish between local and global mode shapes. If multiple individual members show significant MRFs (for example, > 20%), the instability of the entire structure or a substructure is very likely. On the other hand, if the sum of all MRFs for an eigenmode is around 100%, a local stability phenomenon (for example, buckling of a single bar) can be expected.
Furthermore, the MRF can be used to determine critical loads and equivalent buckling lengths of certain members (for example, for stability design). Mode shapes for which a specific member has small MRF values (for example, < 20%) can be neglected in this context.
The MRF is displayed by mode shape in the result table under Stability Analysis → Results by Members → Effective Lengths and Critical Loads.
Several modeling tools are available for elements in building models:
Vertical line
Column
Wall
Beam
Rectangular floor
Polygonal floor
Rectangular floor opening
Polygonal floor opening
This feature allows you to define the element on the ground plane (for example, with a background layer) with the associated multiple element creation in space.
Using the "Load Transfer Only" story type, you can consider slabs without stiffness effects in and out of the plane in the Building Model add-on. This element type collects the loads on the slab and transfers them to the supporting elements of a 3D model. Thus, you can simulate secondary components, such as grillage and similar load distribution elements, without any further effect in the 3D model.
Have you activated the Building Model add-on? Very good! This allows you to display the center of rigidity in tabular and graphical form. Use it for your dynamic analysis, for example.
The Aluminum Design add-on provides you with further options. Here you can also design general cross-sections that are not predefined in the cross-section library. For example, create a cross-section in the RSECTION program and then import it into RFEM/RSTAB. Depending on the design standard used, you can select from various design formats. This includes, for example, the equivalent stress analysis.
With a license for RSECTION and "Effective Sections", you can also perform the design checks while taking into account the effective cross-section properties according to EN 1993‑1‑5.
You know for sure that when connecting tension-loaded components with bolted connections, you need to consider the cross-section reduction due to the bolt holes in the ultimate limit state design. The structural analysis programs also have a solution for this. In the Aluminum Design add-on, you can enter a member local section reduction for this. Enter the reduction of the cross-section as an absolute value or as a percentage of the total area at all relevant locations.
The Torsional Warping (7 DOF) add-on allows you to perform the calculation of member structures in RFEM and RSTAB, taking into account the cross-section warping. You can consider all internal forces (N, Vu, Vv, Mt,pri, Mt,sec, Mu, Mv, Mω) determined in this way in the equivalent stress analysis of the aluminum design. Note: This feature is not yet available for the design standard ADM 2020.
Did you use the eigenvalue solver of the add-on to determine the critical load factor within the stability analysis? In this case, you can then display the governing mode shape of the object to be designed as a result.