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.
The ASCE 7-22 Standard [1], Sect. 12.9.1.6 specifies when P-delta effects should be considered when running a modal response spectrum analysis for seismic design. In the NBC 2020 [2], Sent. 4.1.8.3.8.c gives only a short requirement that sway effects due to the interaction of gravity loads with the deformed structure should be considered. Therefore, there may be situations where second-order effects, also known as P-delta, must be considered when carrying out a seismic analysis.
To evaluate whether it is also necessary to consider the second-order analysis in a dynamic calculation, the sensitivity coefficient of interstory drift θ is provided in EN 1998‑1, Sections 2.2.2 and 4.4.2.2. It can be calculated and analyzed using RFEM 6 and RSTAB 9.
Using an example of a steel fiber-reinforced concrete slab, this article describes how the use of different integration methods and of a different number of integration points affects the calculation result.
When calculating regular structures, data input is often not complicated but time-consuming. Input automation can save valuable time. The task described in the present article is to consider the stories of a house as single construction stages. Data is entered using a C# program so that the user does not have to enter the elements of the individual floors manually.
The National Building Code of Canada (NBC) 2020 Article 4.1.8.7 provides a clear procedure for earthquake methods of analysis. The more advanced method, the Dynamic Analysis Procedure in Article 4.1.8.12, should be used for all structure types except those that meet the criteria set forth in 4.1.8.7. The more simplistic method, the Equivalent Static Force Procedure (ESFP) in Article 4.1.8.11, can be used for all other structures.
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.
If you want to use a pure surface model, for example, when determining the internal forces and moments, but the structural component is still designed on the member model, you can take advantage of a result beam.
Both the determination of natural vibrations and the response spectrum analysis are always performed on a linear system. If nonlinearities exist in the system, they are linearized and thus not taken into account. They are caused by, for example, tension members, nonlinear supports, or nonlinear hinges. This article shows how you can handle them in a dynamic analysis.
The fatigue design according to EN 1992-1-1 must be performed for the structural components subjected to large stress ranges and/or many load changes. In this case, the design checks for the concrete and the reinforcement are performed separately. There are two alternative design methods available.
The Construction Stages Analysis (CSA) add-on allows for the design of member, surface, and solid structures in RFEM 6 considering the specific construction stages associated with the construction process. This is important since buildings are not constructed all at once, but by gradually combining individual structural parts. The single steps in which structural elements, as well as loads, are added to the building are called construction stages, whereas the process itself is called a construction process.
Thus, the final state of the structure is available upon completion of the construction process; that is, all the construction stages. For some structures, the influence of the construction process (that is, all the individual construction stages) might be significant and it should be considered so that errors in the calculation are avoided. A general overview of the CSA add-on is given in the Knowledge Base article titled “Consideration of Construction Stages in RFEM 6”.
This article discusses the options available for determining the nominal flexural strength, Mnlb for the limit state of local buckling when designing according to the 2020 Aluminum Design Manual.
In order to correctly design a downstand beam or a T-beam in RFEM 6 using the Concrete Design add-on, it is essential to determine the flange widths for the rib members. This article describes the input options for a two-span beam and the calculation of the flange dimensions according to EN 1992-1-1.
The calculation of complex structures by means of finite element analysis software is generally performed on the entire model. However, the construction of such structures is a process carried out in multiple stages where the final state of the building is achieved by combining the separate structural parts. To avoid errors in the calculation of overall models, the influence of the construction process must be considered. In RFEM 6, this is possible using the Construction Stages Analysis (CSA) add-on.
With the most recent ACI 318-19 standard, the long-term relationship to determine the concrete shear resistance, Vc, is redefined. With the new method, the member height, the longitudinal reinforcement ratio, and the normal stress now influence the shear strength, Vc. This article describes the shear design updates, and the application is demonstrated with an example.
In RFEM 6, seismic analysis can be done by using the Modal Analysis and the Response Spectrum Analysis add-ons. Once the spectral analysis has been performed, it is possible to use the Building Model add-on to display story actions, interstory drifts, and forces in shear walls.
Building Model is one of the special solution add-ons in RFEM 6. It is an advantageous tool for modeling, with which building stories can be created and manipulated easily. Building Model can be activated at the beginning of the modeling process and afterwards.
RFEM 6 offers the Aluminum Design add-on to design aluminum members for the ultimate and serviceability limit states according to Eurocode 9. In addition to this, you can perform design according to ADM 2020 (US Standard).