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Re: Knee Brace Literature

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Dear Jeremy White,


            To avoid moment connection at the beam-column junction, knee bracing may be provided, if space is available for the same. Some of the basic points regarding knee bracing are listed below which may be helpful to you :


1)        Knee bracings should be modeled in the Space Frame Model.  

2)        Moment at the beam-column junction may be released partially or fully. Knee bracings are to be designed accordingly.

3)        Due to vertical loads, knee bracing will be under Compression. However, due to lateral loads, knee bracing may be under compression or tension, depending upon the direction of the lateral load. Hence, knee bracing and its connection with the beam-column are to be designed for Compressive load as well as for tensile loads.

4)        In the beam and column, at the junction of knee bracing, force in the knee bracing may be resolved in two components (horizontal & vertical). These components will cause bending in the beam & column. Hence, beam and column are to be designed for bending at the junction of knee bracing.

5)        As mentioned above, local concentration of force will be there at the junction of knee bracing and beam, column. Hence, local strengthening may be needed at the junction of knee bracing and beam & column.

6)        If  knee bracings are provided to replace the moment connections, overall deflection of the structure may increase under the effect of lateral loads. To decrease the deflection, partially restrained moment connection may be provided along with the knee bracings.

7)        Beam-column junction may be designed as a shear connection or partially restrained moment connection, depending upon the assumptions considered in Space Frame Model.




Bhavin Shah

On 1/16/06, Jeremy White <jwhite(--nospam--at) > wrote:

I'm working on a two-story steel office building and I'm investigating moment frames vs. knee bracing on our wind frames.  We have plenty of ceiling space so we believe knee braces may be a good alternative to moment connections.  I intuitively understand how knee bracing works, but I want to know if there are any nuances that might be overlooked.  I've checked in some of our steel books around the office and can't find anything that discusses knee bracing (just x and k bracing).  Does anyone know of a good resource for info about knee brace design and/or theory?



Jeremy White