Using the Timber Design add-on, timber column design is possible according to the 2018 NDS standard ASD method. Accurately calculating timber member compressive capacity and adjustment factors is important for safety considerations and design. The following article will verify the maximum critical buckling strength calculated by the Timber Design add-on using step-by-step analytical equations as per the NDS 2018 standard including the compressive adjustment factors, adjusted compressive design value, and final design ratio.
Lateral-Torsional Buckling (LTB) is a phenomenon that occurs when a beam or structural member is subjected to bending and the compression flange is not sufficiently supported laterally. This leads to a combination of lateral displacement and twisting. It is a critical consideration in the design of structural elements, especially in slender beams and girders.
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.
The response spectrum analysis is one of the most frequently used design methods in the case of earthquakes. This method has many advantages. The most important is the simplification: It simplifies the complexity of earthquakes so far that the design can be performed with reasonable effort. The disadvantage of this method is that a lot of information is lost due to this simplification. One way to moderate this disadvantage is to use the equivalent linear combination when combining the modal responses. This article explains this option by describing an example.
The modal relevance factor is a result of the linear stability analysis and qualitatively describes the degree of participation of individual members in a specific mode shape.
The “Modal Analysis” add-on in RFEM 6 allows you to perform modal analysis of structural systems, thus determining natural vibration values such as natural frequencies, mode shapes, modal masses, and effective modal mass factors. These results can be used for vibration design, as well as for further dynamic analyses (for example, loading by a response spectrum).
This article will show you how to use the Combination Wizard in RFEM 6 to reduce the number of load combinations to be analyzed, thus reducing the calculation effort and increasing the calculation efficiency.
This article will show you how to use the Torsion Warping (7 DOF) add-on in combination with the Structure Stability add-on to consider cross-section warping as an additional degree of freedom when performing the stability analysis.
Modal analysis is the starting point for the dynamic analysis of structural systems. You can use it to determine natural vibration values such as natural frequencies, mode shapes, modal masses, and effective modal mass factors. This outcome can be used for vibration design, and it can be used for further dynamic analyses (for example, loading by a response spectrum).
In accordance with Sect. 6.6.3.1.1 and Clause 10.14.1.2 of ACI 318-19 and CSA A23.3-19, respectively, RFEM effectively takes into consideration concrete member and surface stiffness reduction for various element types. Available selection types include cracked and uncracked walls, flat plates and slabs, beams, and columns. The multiplier factors available within the program are taken directly from Table 6.6.3.1.1(a) and Table 10.14.1.2.
The stability checks for the equivalent member design according to EN 1993-1-1, AISC 360, CSA S16, and other international standards require consideration of the design length (that is, the effective length of the members). In RFEM 6, it is possible to determine the effective length manually by assigning nodal supports and effective length factors or, on the other hand, by importing it from the stability analysis. Both options will be demonstrated in this article by determining the effective length of the framed column in Image 1.
This technical article presents some basics for using the Torsional Warping add-on (7 DOF). It is fully integrated into the main program and allows you to consider the cross-section warping when calculating member elements. In combination with the Stability Analysis and Steel Design add-ons, it is possible to perform the lateral-torsional buckling design with internal forces according to the second-order analysis, taking imperfections into account.
RFEM and RSTAB can calculate the critical load factor for each load case (LC) and each load combination (CO) in the case of a geometrically nonlinear calculation (second-order analysis and following).
In RF-/FOUNDATION Pro, the foundation design requires the definition of the corresponding loading (load cases, load combinations, or result combinations) for different design situations (STR, GEO, UPL, or EQU).
The dialog box for editing load or result combinations is a non-modal dialog box. This means that after you open this dialog box, you can edit the combinations outside the dialog box as well. For manually defining or editing a combination, a separate dialog box can be opened parallel to the "Edit load cases and combinations" dialog box.
The RF-STABILITY add-on module determines any critical load factors, effective lengths, and eigenvectors of RFEM models. Stability analyses can be carried out by various eigenvalue methods, the advantages of which depend on the structural system as well as computer configurations.
In RF‑TENDON and RF‑TENDON Design, you can review and adjust the code‑dependent factors, calculation parameters, and calculation methods using the "Code" button. You can display the settings and adjustment options according to a chapter of a code, selecting the "Grouping" option in the dialog box.
In the case of using slow‑curing concrete (usually for thick components), you can reduce the calculated minimum reinforcement by a factor of 0.85 to apply the load due to restraint, according to EN 1992‑1‑1, Section 7.3.2. However, a precondition for reduction is that the characteristic value of the strength development r = fcm2 / fcm28 does not exceed 0.3. Other key requirements for the application of this reinforcement reduction are specified explicitly in the final planning documents.
By means of result combinations, it is possible to create, among other things, the envelopes for internal forces and deformations. Thus, you can quickly find the maxima and minima for the subsequent design.
The automatic creation of combinations in RFEM and RSTAB with the "EN 1990 + EN 1991‑3; Cranes" option allows you to design crane runway beams as well as support loads on the rest of the structure.
For automatic load case combination in RFEM and RSTAB, you have to enter the possible interaction of load cases. In addition to the simultaneous or alternative occurrence of all load cases of an action, an option for different combination conditions is possible.
When calculating foundations according to EC 7 or EC 2, different foundation types or sizes are usually used in one object. However, boundary conditions like the soil parameters, the materials for foundations, concrete covers, and the load combinations selected for design remain the same for all foundations, as a rule.
In the case of horizontal beam-like supporting structures, the favorable and unfavorable load components of the permanent actions should be considered separately. In RFEM and RSTAB, you can do this as follows.
The most common causes of unstable models are failing member nonlinearities such as tension members. As the simplest example, there is a frame with supports on the column footing and moment hinges on the column head. This unstable system is stabilized by a cross bracing of tension members. In the case of load combinations with horizontal loads, the system remains stable. However, if it is loaded vertically, both tension members fail and the system becomes unstable, which causes a calculation error. You can avoid such an error by selecting the exceptional handling of failing members under "Calculate" → "Calculation Parameters" → "Global Calculation Parameters".
In RFEM and RSTAB, you can define a user-defined combination scheme. This can be helpful if a desired combination scheme cannot be created from a standard. In such cases, you can export the created load cases to Excel, create the scheme there, then import them to RFEM or RSTAB.