FAQ 005126 | Modal Analysis - Minimum Initial Strain
Model Used in
Plate Poisson's Ratio Equal to 0
Number of Nodes | 4 |
Number of Lines | 4 |
Number of Members | 0 |
Number of Surfaces | 1 |
Number of Solids | 0 |
Number of Load Cases | 4 |
Number of Load Combinations | 0 |
Number of Result Combinations | 0 |
Total Weight | 0.079 tons |
Dimensions (Metric) | 10,000 x 0,000 x 10,000 m |
Dimensions (Imperial) | 32.81 x 0 x 32.81 feet |
You can download this structural model to use it for training purposes or for your projects. However, we do not assume any guarantee or liability for the accuracy or completeness of the model.
![Building Overview (KB1866)](/en/webimage/046746/3676167/KB1866_image01_en_Model.png?mw=512&hash=18feed6e03b6c09c60d7e29dc96041d95c24997b)
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.
![Reduction of Building to Cantilever Structure The individual mass points represent stories. The deflection due to the normal compression forces shown in (a) is (b) converted into equivalent moments of displacement or shear forces (KB1867)](/en/webimage/046751/3675982/KB1867_image01_building_replacement_system_as_cantilever.png?mw=512&hash=2810652c31c299316a7e4564086f5e5f9b5889b2)
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.
![Modal Analysis of Masses from Load Case](/en/webimage/031338/3309253/1_en.png?mw=512&hash=fd421b3f2c85d04e163841c3e5995f948391dd20)
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.
![Activating the Modal Analysis Add-on and Selecting the Design Standard](/en/webimage/031494/3312974/1_EN.png?mw=512&hash=0cb20064fea2605fa0436c92cc8f377eb2cbb465)
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).
![Feature 002671 | Seismic Design of Reinforced Concrete Members According to EC 8](/en/webimage/043980/3609964/43980.png?mw=512&hash=6b308b2caaa2cf5340fbd88a9ea7eb2e201e6890)
The Concrete Design add-on allows you to perform the seismic design of reinforced concrete members according to EC 8. This includes, among other things, the following functionalities:
- Seismic design configurations
- Differentiation of the ductility classes DCL, DCM, DCH
- Option to transfer the behavior factor from a dynamic analysis
- Check of the limit value for the behavior factor
- Capacity design checks of "Strong column - weak beam"
- Detailing and particular rules for curvature ductility factor
- Detailing and particular rules for local ductility
![Add-on "Steel Joints for RFEM 6" | Component Library](/en/webimage/043097/3898884/steel_joints_components.png?mw=512&hash=e4f835906155863fc7019d5043b22e553dc766f9)
- Numerous component types, such as base and end plates, web angles, fin plates, gusset plates, stiffeners, tapers, or ribs for easy input of typical connection situations
- Universally applicable basic components (such as plates, welds, bolts, auxiliary planes) for modeling complex connection situations
- Graphical display of the connection geometry with dynamic updating during the input
- Wide range of cross-section shapes: I-sections, U-sections, angles, T-sections, hollow sections, built-up cross-sections and thin-walled sections
- Library in the Dlubal Center with a large number of program-side template connections, including user-defined templates
- Automatic adaptation of the connection geometry based on the relative arrangement of the components to each other – even in case of subsequent editing of the structural components
![Feature 002840 | Graphical Add-on Result Display by Design Situation](/en/webimage/051593/3982947/Bemessungssituation.png?mw=512&hash=7fd0d9a61cbc8d701205795390d25dfae3caa76b)
In the Navigator – Results, you can select the design situations for which you want to display the add-on results graphically.
![Feature 002843 | Dimensioning with Result Function](/en/webimage/051576/3982510/1.png?mw=512&hash=9d7f6c198b6d4ae6ee8f2fa8bca75f85579e14c9)
For design objects, you can optionally display sags or extreme results.