A knee brace is a short diagonal member running between a column and a beam or girder, close to the joint. It shortens the effective span of the beam and stiffens the frame against lateral drift, without the full-height diagonal that a vertical brace needs. The brace force arrives at the joint as axial load, and a gusset plate takes it into the column or girder.
SkyCiv Connection Design checks the knee brace connection to AISC 360-16 en TSA ou LRFD. You enter the supporting member, the brace, the gusset plate and the fixtures, and it returns every check with its utilization ratio and the clause behind it.
Why Use a Knee Brace
A knee brace buys stiffness cheaply. It uses less steel than a full diagonal and it is quick to erect, because it is a short member with one connection at each end. Because it sits in the corner of the bay rather than across it, it leaves the opening largely clear, which matters where a full-height brace would block a door, a window or a services run.
It is also a practical retrofit. Adding a knee brace to an existing frame means working at one joint rather than rebuilding a bay, so it is a common way to stiffen a structure that has been reassessed or reloaded.
The trade-off is that the brace attracts moment into the beam and the column at the brace point. The members either side of the connection have to be checked for that, which is a frame analysis question rather than a connection one.
Designing a Knee Brace Connection in SkyCiv
The design code can be AISC 360-16 ASD ou LRFD, and units English/Imperial or SI/Metric. The knee brace is available framing to a column flange, a column web or a girder flange. Clique le “Gousset directement soudé” tuile.
Détails Onglet
Record the project details here. None of it changes the calculations, but it carries into the report.
Onglet Assemblage
Three tabs sit under Assembly: the Column or Girder, the Brace, and the Connection, which holds the gusset plate.
Onglet Poteau ou Poutre
Specify the section and material grade of the supporting member, whichever the brace frames into.
Onglet Renfort
The brace can be a single angle, a double angle, a square or rectangular HSS, or a WT section. The shape drives how the brace attaches to the gusset: an angle connects through one leg, which puts the load off the brace centreline, while an HSS is usually slotted over the plate and welded on both faces.
Onglet Connexion
Set the gusset plate properties here. The plate has to be large enough for the weld or bolt group at the brace end and still fit against the supporting member, so watch the 3D renderer as you size it.
Onglet Calendrier
Two interfaces are set here: gusset plate to brace, and gusset plate to the column or girder support. Each can be bolted or welded.
Where the connection is bolted, the bolt grades are A307, A325, A490 or Custom. A325 and A490 are grades within ASTM F3125, which consolidated the older standalone specifications. Where it is welded, spécifier le matériau de soudure, or ‘Custom’ with your own Fnw, and the weld size.
For more on the fastener side, voir la documentation sur boulons et soudures.
Onglet Charges
Enter the brace loads here. Hover the tooltips for the sign convention and direction of each.
Match the loads to the design method you picked at the start. LRFD takes factored loads against design strength; ASD takes service loads against allowable strength. The software cannot tell which you typed.
Onglet Résultats
Cliquez sur “Exécuter des vérifications de conception”. Anything missing from the earlier tabs is flagged here rather than silently defaulted.
The summary shows whether the connection passed, with a utilization ratio against each check. S'il a échoué, change the inputs on the earlier tabs and click “Réexécuter les vérifications de conception”. When it passes, survoler “rapport” and pick “Rapport sommaire” ou “Rapport complet”.
That is an extract from the full report. Each check carries its reference to the AISC manual or specification, and the working follows the order the specification uses, so a reviewing engineer can read it line by line instead of reverse-engineering a number.
IciIl s'agit d'une copie PDF du rapport de calcul détaillé complet.
Try It Yourself
Pick the knee brace, enter your brace, gusset and loads, and see every check with its code reference. Il s'exécute dans le navigateur, avec rien à installer.
See also the knee brace connection calculator, et la chevron brace et contreventement vertical calculators for the other bracing configurations.
