The evaluation of story drift in a building is crucial to ensure acceptable structural performance by limiting the drift amount. Excessive drift has the potential to induce system instability and may cause damage to nonstructural components such as partitions. This article outlines the procedure for establishing interstory drift according to ASCE 7-22 and the Building Model add-on in RFEM 6.
Understanding steel connection rigidity is crucial in structural design. Often, connections are treated as strictly pinned or rigid, but this can lead to uneconomical or even dangerous design checks. Explore how Dlubal Software's RFEM and Steel Joints add-on help verify connection stiffness and moment resistance, ensuring safer and more economical design checks.
This article presents the basic concepts in structural dynamics and their role in the seismic design of structures. Great emphasis is given to explaining the technical aspects in an understandable way, so that readers without deep technical knowledge can gain an insight into the subject.
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.
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.
For the ultimate limit state design, EN 1998‑1, Sections 2.2.2 and 4.4.2.2 require a calculation considering the second‑order theory (P‑Δ effect). This effect may be neglected only if the interstory drift sensitivity coefficient θ is less than 0.1.
The Geotechnical Analysis add-on provides RFEM with additional specific soil material models that are able to suitably represent complex soil material behavior. This technical article is an introduction to show how the stress-dependent stiffness of soil material models can be determined.
In this article, a lap joint of a ZL purlin on a monopitch roof is modeled and designed using the Steel Joints add-on, and compared with the load-bearing capacity table of the manufacturer.
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.
Given that realistic determination of the soil conditions significantly influences the quality of the structural analysis of buildings, the Geotechnical Analysis add-on is offered in RFEM 6 to determine the soil body to be analyzed.
The way to provide data obtained from field tests in the add-on and use the properties from soil samples to determine the soil massifs of interest was discussed in Knowledge Base article “Creating Soil Body from Soil Samples in RFEM 6”. This article, on the other hand, will discuss the procedure to calculate settlements and soil pressures for a reinforced concrete building.
The dynamic analysis in RFEM 6 and RSTAB 9 is divided into several add-ons. The Modal Analysis add-on is a prerequisite for all other dynamic add-ons, since it performs the natural vibration analysis for member, surface, and solid models.
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).
You can model and analyze masonry structures in RFEM 6 with the Masonry Design add-on that employs the finite element method for the design. Complex masonry structures can be modeled, and static and dynamic analysis can be performed, given that a nonlinear material model is implemented in the program to display the load-bearing behavior of masonry and the different failure mechanisms. You can enter and model masonry structures directly in RFEM 6 and combine the masonry material model with all common RFEM add-ons. In other words, you can design entire building models in connection with masonry.
The quality of the structural analysis of buildings is significantly improved when the soil conditions are considered as realistically as possible. In RFEM 6, you can realistically determine the soil body to be analyzed with the help of the Geotechnical Analysis add-on. This add-on can be activated in the model’s Base Data as shown in Image 01.
The advantage of the RFEM 6 Steel Joints add-on is that you can analyze steel connections using an FE model for which the modeling runs fully automatically in the background. The input of the steel joint components that control the modeling can be done by defining the components manually, or by using the available templates in the library. The latter method is included in a previous Knowledge Base article titled “Defining Steel Joint Components Using the Library". The definition of parameters for the design of steel joints is the topic of the Knowledge Base article “Designing Steel Joints in RFEM 6".
Steel connections in RFEM 6 are defined as an assembly of components. In the new Steel Joints add-on, universally applicable basic components (plates, welds, auxiliary planes) are available for entering complex connection situations. The methods with which connections can be defined are considered in two previous Knowledge Base articles: “A Novel Approach to Designing Steel Joints in RFEM 6" and “Defining Steel Joint Components Using the Library".
You can use the Steel Joints add-on in RFEM 6 to create and analyze steel connections using an FE model. You can control the modeling of the connections via a simple and familiar input of components. Steel joint components can be defined manually, or by using the available templates in the library. The former method is included in a previous Knowledge Base article titled “A Novel Approach to Designing Steel Joints in RFEM 6". This article will focus on the latter method; that is, it will show you how to define steel joint components using the available templates in the program’s library.
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.
Seismic Analysis in RFEM 6 is possible using the modal analysis and the response spectrum analysis add-ons. As a matter of fact, the general concept of the earthquake analysis in RFEM 6 is based on the creation of a load case for the modal analysis and the response spectrum analysis, respectively. The standard groups for these analyses are set in the Standards II tab of the model’s Base Data.
One of the innovations in RFEM 6 is the approach to designing steel connections. In contrast to RFEM 5, where the design of steel joints is based on an analytical solution, the Steel Joints add-on in RFEM 6 offers an FE solution for steel connections.
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.