2749x

2021-01-22

Finding System Instabilities

A calculation break‑off due to an unstable system can have different reasons. On one hand, it can indicate a "real" instability due to overloading of the system; on the other hand, the error message can result from inaccuracies in the model.

To find modeling errors in the structural system, RFEM provides several elegant options to localize and analyze them. For this, a feature has also been implemented in the RF‑STABILITY module: The "Calculate buckling shape for unstable model so that causes of instability can be checked graphically" option allows you to calculate supposedly unstable structural systems. With the model data, the module performs an eigenvalue analysis so that the result of the instability of the affected structural component is shown graphically. This method is particularly suited to find, for example, members that are not connected or that have too many open degrees of freedom.

Steel Hall

Author

Mr. Lex is responsible for developing products for glass structures and for quality assurance of the RFEM program. He also provides technical support for our customers.

Links

Stability Analysis Software

Do you have any questions?

Events

2024-04-24

Online Training

RFEM 6 | Students | Introduction to FEM

2024-04-25

Stiffening Design in RFEM 6 Using Building Model

Webinar

Stiffening Design in RFEM 6 Using Building Model

2024-04-25

AISC 360-22 Steel Connection Design in RFEM 6

Webinar

AISC 360-22 Steel Connection Design in RFEM 6 (USA)

2024-04-30

Online Training

RFEM 6 | Students | Introduction to Timber Design

2024-05-02

Construction Stages in Membrane Structures with RFEM 6

Webinar

Construction Stages in Membrane Structures with RFEM 6

2024-05-08

Online Training

RFEM 6 | Students | Introduction to Reinforced Concrete Design

2024-05-08

$Cross-Section Modeling and \n Stress Analysis in RSECTION 1$

Webinar

Cross-Section Modeling and Stress Analysis in RSECTION 1

2024-05-15

Online Training

RFEM 6 | Students | Introduction to Steel Design

2024-05-16

Consideration of Construction Stages in RFEM 6

Webinar

Consideration of Construction Stages in RFEM 6

2024-05-23

Most Frequently Asked Questions Answered by Dlubal Support Team

Webinar

Most Frequently Asked Questions Answered by Dlubal Support Team | May 2024

2024-05-29

$Steel Structures in RFEM 6 \n Part 1: Modeling, Load Input$

Webinar

Modeling and Design of Steel Structures in RFEM 6 | Part 1: Modeling, Load Input

2024-06-06

$Steel Structures in RFEM 6 \n Part 2: Combinations, Design, Documentation$

Webinar

Modeling and Design of Steel Structures in RFEM 6 | Part 2: Combinations, Design, Documentation

Videos

Knowledge Base

KB 000573 | Finding System Instabilities

Length: 00:00:18 min

Knowledge Base

KB 000934 | Eigenvalue Methods in RF-STABILITY

Length: 00:00:51 min

Knowledge Base

KB 000804 | Activating Internal Member Division for Stability Analysis

Length: 00:00:26 min

Knowledge Base

KB 000827 | Find Mode Shapes from Critical Load Factor

Length: 00:00:49 min

Knowledge Base

KB 001681 | Determination of Ideal Spring Stiffness for Lateral Supports at Buckling Members

Length: 00:00:44 min

Knowledge Base

KB 001669 | Lateral-Torsional Buckling in Timber Construction | Examples 2

Length: 00:02:15 min

Event

Webinar | FEA Troubleshooting and Optimization in RFEM

Length: 01:07:06 min

Event

Invitation to Online Training "Steel Structures | Eurocode 3 "

Length: 00:01:20 min

Knowledge Base

KB 001626 | Steel Frame Considering Connection Stiffness

Length: 00:00:53 min

Playlist

Models to Download

455x

34x

Steel Hall

491x

13x

Verification Example 0096 | 1

490x

Verification Example 0096 | 2

479x

Verification Example 0096 | 3

476x

Verification Example 0096 | 4

1504x

92x

Truss Girder

3D Model of Single Element in RFEM (© Jing Kong & Associates Consulting Structural Engineers Inc.)

760x

Hybrid Structure Made of Timber and Steel

663x

79x

Truss Girders

1001x

46x

Stabilized Buckling Member

Knowledge Base Articles

Find Mode Shapes from Critical Load Factor

The function, which is also known as shifting, allows you to calculate critical load factors beyond a user‑defined initial value. Determination of the critical load factors is usually done from the smallest to the greatest critical load factor.

If a member is supported laterally to prevent buckling due to a compressive axial force, it must be ensured that the lateral support is actually able to prevent buckling. Therefore, the aim of this article is to determine the ideal spring stiffness of a lateral support using the Winter model.

The previous article, titled Lateral-Torsional Buckling in Timber Construction | Examples 1, explains the practical application for determining the critical bending moment M_crit or the critical bending stress σ_crit for a bending beam's lateral buckling using simple examples. In this article, the critical bending moment is determined by considering an elastic foundation resulting from a stiffening bracing.

Screenshots

Finding System Instabilities

Steel Hall

Verification Example 0096 | 4

Verification Example 0096 | 3

Verification Example 0096 | 2

Form-Finding, Z-Axis Direction View, Deformation

Form-Finding, Z-Axis Direction View

Form-Finding, Y-Axis Direction View, Deformation

Form-Finding, Y-Axis Direction View

Product Features

Use the "Independent mesh preferred" option in the FE mesh settings to create an independent FE mesh for the integrated objects. This allows you to generate a significantly more detailed and precise FE mesh for individual objects that are integrated into one another.

Feature 002807 | 3D Display of FSM Results

In the "Edit Section" dialog box, you can display the buckling shapes of the Finite Strip Method (FSM) as a 3D graphic.

In RFEM 6 and RSTAB 9, you have the option to enter "Visual Objects" as guide objects. You can import the file formats 3ds, stl, and obj.

These objects allow you to create a better reference to the dimensions.

Feature 002801 | Punching Shear Design for All Section Shapes

Do you have individual column sections and angled wall geometries, and need punching shear design for them?

No problem. In RFEM 6, you can perform punching shear design not only for rectangular and circular sections, but for any cross-section shape.

Frequently Asked Questions (FAQ)

What is the critical load factor and how is it possible to determine it?

I have calculated a pre-deformed structure according to the second-order analysis with RF‑STABILITY and RF‑IMP. Why are the deformations of the CO smaller than the applied pre-deformation?

Is it possible to perform stability analyses on reinforced concrete structures by means of RF‑STABILITY?

My model is unstable. What can be the cause?

How can I perform a stability/buckling analysis on a plate structure?

Is it possible to import effective lengths from RF‑STABILITY or RSBUCK in RF‑/TIMBER Pro?

Customer Projects

Pedestrian and Cyclist Bridge "Herzogsteg" in Eichstätt, Germany

Lighted Toll Station | © Mr. Yunchao Ding, Jiangsu Jingong Space Structure Co., Ltd.

Dawang Toll Station in Shaanxi, China

RFEM Model of High-Bay Racking with Deformation Results

High-Bay Racking, China

Multi-Energy Station in Les Sables-d'Olonne, France

Siegrist Igor Carpenteria Warehouse in Maggia, Switzerland

Front View of Office Building with V-Shaped Steel Composite Columns | © Die Tragwerker GmbH

Office Building with Integrated Visitor Center and Parking Garage in Geiselbulach, Germany

Metz Gym as Showcase of Engineering and Sustainability in Modern Construction, Metz, France

Steel Pergola at Rafael Landívar University (© Eng. Enrique de León)

Steel Pergola in Plaza del Edificio L, Rafael Landívar University, Guatemala

Radar Tower on Left (© SAQQARA Ingeniería)

Structural Analysis of Radar Tower at Malaga Airport, Spain

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