Effective Lengths for Steel Stability Design

How do I define effective lengths when designing steel members in RFEM 6?

There are two options when it comes to defining effective lengths in RFEM 6. First, edit the member and navigate to the "Design Types" Tab. Second, create a new effective lengths definition.

Third, set whether you would like to calculate the critical moment according to an Eigenvalue method or Chapter F. from the AISC. Fourth, navigate to the "Nodal Supports and Effective Lengths" tab. Within this tab there are two different methods that can be used.

Method 1: Nodal Supports

Referencing Member No. 1 in the attached model, for this column you can see a how the effective lengths for the Start, End, and Intermediate nodes are defined. First, click on the Select Member or Member Set and then select the member. This will activate the intermediate nodes along the member length in the table. Next, check whether the node can move in the y/z axis (weak/strong axis), rotate about its local x axis (torsion), and about its local z axis.

Top and bottom flanges can also be restrained separately by releasing (unchecking) the rotation about the local x axis restraint (torsion).

Method 2: "K" Factors and Absolute Values

Referencing Member No. 5 in the attached model, the effective length factors can be used to define the unbraced length directly and/or apply the appropriate member end conditions. To adjust the unbraced lengths directly instead of utilizing the nodes on member (Method 1), the "K" factors can be entered manually in the table below. Or the "Absolute Values" can be entered by checking on the option "Absolute Values". Then the unbraced length itself can be entered manually instead. This method is best used when there are no intermediate node(s) currently present on the member.

Keywords

Write Comment...

Write Comment...

• Views 171x
• Updated 04/25/2022

Submit Individual Question

CFD Wind Simulation with RWIND 2

Webinar 06/29/2022 2:00 PM - 3:00 PM EDT

RFEM 6 | Basics | USA

Online Training 07/20/2022 12:00 PM - 4:00 PM EDT

RFEM 6 | Basics

Online Training 07/29/2022 9:00 AM - 1:00 PM CEST

Eurocode 2 | Concrete Structures According to DIN EN 1992-1-1

Online Training 08/12/2022 8:30 AM - 12:30 PM CEST

Eurocode 3 | Steel Structures According to DIN EN 1993-1-1

Online Training 09/08/2022 9:00 AM - 1:00 PM CEST

Eurocode 5 | Timber Structures According to DIN EN 1995-1-1

Online Training 09/15/2022 9:00 AM - 1:00 PM CEST

RFEM 6 | Dynamic Analysis and Seismic Design According to EC 8

Online Training 09/21/2022 9:00 AM - 1:00 PM CEST

RFEM 6 | Basics

Online Training 10/07/2022 9:00 AM - 1:00 PM CEST

Eurocode 2 | Concrete Structures According to DIN EN 1992-1-1

Online Training 10/14/2022 9:00 AM - 1:00 PM CEST

Eurocode 3 | Steel Structures According to DIN EN 1993-1-1

Online Training 11/17/2022 9:00 AM - 1:00 PM CET

RFEM 6 | Dynamic Analysis and Seismic Design According to EC 8

Online Training 11/23/2022 9:00 AM - 1:00 PM CET

Eurocode 5 | Timber Structures According to DIN EN 1995-1-1

Online Training 12/08/2022 9:00 AM - 1:00 PM CET

Eurocode 5 | Timber Structures According to DIN EN 1995-1-1

Online Training 06/15/2022 8:30 AM - 12:30 PM CEST

RFEM 6 for Students | USA

Online Training 06/08/2022 1:00 PM - 4:00 PM EDT

Webinar 05/25/2022 2:00 PM - 3:00 PM EDT

RFEM 6 | Students | Introduction to Timber Design

Online Training 05/25/2022 4:00 PM - 5:00 PM CEST

RFEM 6 | Students | Introduction to Reinforced Concrete Design

Online Training 05/19/2022 4:00 PM - 5:00 PM CEST

ASCE 7-16 Response Spectrum Analysis in RFEM 6

Webinar 05/05/2022 2:00 PM - 3:00 PM EDT

Length 3:01:09 min

Length 1:00:51 min

Length 1:01 min

Length 1:04 min