Wind direction plays a crucial role in shaping the outcomes of Computational Fluid Dynamics (CFD) simulations and the structural design of buildings and infrastructures. It is a determining factor in assessing how wind forces interact with structures, influencing the distribution of wind pressures, and consequently, the structural responses. Understanding the impact of wind direction is essential for developing designs that can withstand varying wind forces, ensuring the safety and durability of structures. Simplified, the wind direction helps in fine-tuning CFD simulations and guiding structural design principles for optimal performance and resilience against wind-induced effects.
This article describes how a flat slab of a residential building is modeled in RFEM 6 and designed according to Eurocode 2. The plate is 24 cm thick and is supported by 45/45/300 cm columns at distances of 6.75 m in both the X and Y directions (Image 1). The columns are modeled as elastic nodal supports by determining the spring stiffness based on the boundary conditions (Image 2). C35/45 concrete and B 500 S (A) reinforcing steel are selected as the materials for the design.
An FE mesh quality display is available in RFEM as a tool for structural analyses of two-dimensional components. It leads to the execution of an internal check of the generated finite elements for defined criteria.
In RFEM, it is possible to display the resultant of a section or release. This article explains which part of the sectional area is affected. The easiest way would be to refer the resultant to a cut face of the surface. However, since a section may run through several surfaces with different local coordinate systems, determination by means of a cut face is not possible.
If you want to consider guide objects in the overall view (F8 key or double-click on the mouse wheel) or, for example, in a particular direction of the views, you can enable this option in the settings of the particular guide objects (guidelines, background layers, line grids).
In the RF-/TIMBER Pro, RF-/TIMBER AWC, and RF-/TIMBER CSA add-on modules, you can consider the resulting deformation of a member or set of members. In addition to the local directions y and z, you have the option "R." This allows you to compare the total deflection of a girder to the limit values given in the standards.
In the RF-GLASS add-on module, 3D rendering is implemented to facilitate the definition of the support conditions. This interactive graphical visualization facilitates the input and control of line and nodal supports. However, the schematic display can also be selected, if necessary.
You can color the surfaces in the direction of the local z‑axis using the indicated option in the Display Navigator. By default, the side lying in the negative z-direction is colored red and the side lying in the positive z-direction is colored blue.
In order to detect the governing internal forces of a plate, a checkerboard loading is commonly used. Since it is not necessary to divide the surface into individual load segments, loading is usually carried out by means of free rectangular loads. In the case of many loads, the normal load display can become somewhat confusing.
Before creating a structural model, every user gives thought to the boundary parameters of the system and how best to represent the model. Special attention should be paid to the orientation of the global coordinate system. In engineering, the global Z‑axis is usually oriented downwards (in the direction of the dead load), while it tends to be upwards in architecture. These differences can often lead to complications during modeling; for example, when you replace global models or DXF layers.
When using the RF‑GLASS add‑on module, you can define just the geometry in the main program, as well as the load situation of the structural component to be designed. The respective support conditions and all further design-relevant definitions (for example, the layer structure and support conditions), can be further specified in RF‑GLASS.
In RFEM 5 and RSTAB 8, you can generate surface loads like wind and snow by means of the implemented load generator. On frameworks, these surface loads are also displayed as surface loads in the graphic by default.
In many cases, it is necessary to filter the results for the display of values on surfaces so as not to show all the numbers. In displaying the reinforcement arrangement, you can, for example, hide values that are below the already used basic reinforcement.
In RFEM 5 and RSTAB 8, you can display the resulting support force related to the centroid of the model. It can be used, for example, to check the model and load data.
The determined values for the influence ordinates are displayed as decimal numbers with up to six decimal places by default. This is usually sufficient for the influence lines of internal forces.
The shear force resistance VRd,c without computational shear force reinforcement according to 6.2.2 of EN 1992-1-1 [1] or 10.3.3 of DIN 1045-1 [2] is calculated depending on the longitudinal reinforcement ratio. If the required longitudinal reinforcement from the bending design is used for the calculation of VRd,c, this leads to an underestimation of the shear force resistance without shear reinforcement in the vicinity of the hinged end supports. In contrast to the shear force, the required bending reinforcement decreases in the direction of the support. Furthermore, the actually inserted longitudinal reinforcement usually deviates significantly from the required bending reinforcement in the end support area (for example, in the case of non-staggered beam reinforcement).
In RF‑CONCRETE Surfaces, the design of the surface reinforcement is done by means of a freely definable reinforcement mesh. In RF‑CONCRETE Surfaces, you can display the reinforcement direction by activating the reinforcement arrow that represents it.
For structural reasons, it may be necessary for a base plate not to be set centrically on a foundation. Therefore, an eccentric arrangement of the base plate is possible in RF‑/JOINTS Steel - Column Base by entering the parameters for the respective direction in Window 1.4.
The structural analysis of a girder grillage is usually easy when using computer-aided calculation. There are different options for displaying and analyzing a structure. The conventional kind of structural analysis of components as well as modeling the entire structure are among the possibilities.
In theory, an ideal gas consists of freely moving mass particles without extension in a volume space. In this space, each particle moves at a speed in one direction. The collision of one particle with another particle or the volume limitations leads to a deflection and a change in the speed of the particles.
In the case of a large amount of reinforcement, it might be useful to grade the longitudinal reinforcement of a beam, which means: curtailment. The grading corresponds to the tensile force distribution. Using RF-CONCRETE Members and CONCRETE, you can specify the curtailment of the reinforcement, which is considered in the automatically proposed reinforcement for the longitudinal reinforcement. When determining this reinforcement proposal, it is necessary to ensure that the envelope of the acting tensile force can be absorbed.
The following structure is covered as Example IV.10 in [1] "Comment on Eurocode 3". For a support with a linearly varying cross‑section, a sufficient ultimate limit state design (cross‑section check and stability analysis) is to be performed. Due to the unequal structural component, it is necessary to perform the stability analysis (from the main support direction) using the method according to Section 6.3.4, or alternatively, according to the second‑order analysis.
Composite beams in a three-dimensional analysis are usually connected with orthotropic plates. In that case, the longitudinal direction of the plate stiffness is defined by a main beam and the transverse direction by an orthotropic plate. The stiffness of the plate in the longitudinal direction is set almost to zero. This article explains the determination of stiffnesses in the orthotropic plate.
You can now use axial expansion joints in RF‑PIPING. These are applied to absorb movements of extension and compression in the axis direction due to the thermal expansions of the piping.
There are two ways to specify eccentric nodal loads in RF-/FE-LTB. First, the nodal load has to be applied in the right direction. Then, you can assign either the resulting torsional moment or the eccentricity.