> ## Documentation Index
> Fetch the complete documentation index at: https://calcs.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# General HSS Truss Connection (T, K, Y, X, KT)
> Auto-classify and design HSS truss joints, including gapped and overlapped KT, to AISC 360-22 and Design Guide 24.
**Where you can use this:** [Atlas Tube HSS Connections Hub](https://connectionshub.atlastube.com/login/organisations?src=CALCSDOCS) only
**Status:** Beta · **Region:** US · **Design codes:** AISC 360-22, AISC Design Guide 24 (2nd ed.)
## What this calculator does
Designs HSS truss connections where branch members frame into a chord. The sheet auto-classifies the joint from geometry and force balance, so you do not have to know the joint type before you start, which is usually the case in real truss work.
Supported classifications:
| Joint | Chord shape | Configuration |
| ------- | --------------------- | --------------------- |
| T, Y, X | Round and rectangular | Single branch |
| K | Round and rectangular | Gapped and overlapped |
| KT | Round | Gapped |
| KT | Rectangular | Gapped and overlapped |
## Video walkthrough
Jason McNeil, PE, walks the calculator step by step, showing how it classifies connections from loading and geometry together and then runs the code checks. Useful if you design modified Warren trusses or work through K, T, Y and KT joints.
There is also a shorter video on the [overlapped round K connection](https://www.youtube.com/watch?v=veCsLTB4yHM).
## Inputting key properties
1. **Enter chord and branch sections and material strengths.**
2. **Set the number of branches.** Three branches plus a round chord shape is what unlocks the KT gap classification.
3. **Enter the connection geometry:** branch angles, gap or overlap configuration, and the connection eccentricity.
4. **Enter weld type and size.**
5. **Enter branch axial demands** under ASD or LRFD, in factored or unfactored input mode.
Eccentricity is not optional for KT classification. The joint is classified from the branch sections **and** the eccentricity together, so leaving eccentricity at zero returns a "connection not supported" flag rather than a design. Enter the real eccentricity of your joint and the classification, and its calculations, appear automatically throughout the sheet.
## How KT joints are handled
### Gapped round KT
For a three-branch round HSS joint that classifies as a gapped KT, the sheet decomposes the joint into K1 and K2 gapped K sub-connections and designs each per AISC Design Guide 24, Section 9.6.
Before running the capacity checks it verifies:
* Vertical equilibrium of the three branch forces
* Gap limits
* Connection eccentricity
* Chord and branch wall slenderness and width-ratio limits of applicability
Equilibrium outcomes and the KT gapped sub-connection assumptions are surfaced in the sheet rather than buried.
### Overlapped rectangular KT
Three-branch rectangular joints that classify as overlapped KT are designed in the same sheet. The calculator evaluates the overlap and applies the overlapped KT limit states used by the dedicated overlapped path, including chord plastification, branch local checks and weld strength. Connection diagrams show the overlapped three-branch layout.
## Reviewing the calculations
| Limit state | Reference |
| --------------------------------------------------------------------------- | ----------------------------------------- |
| Limits of applicability, chord slenderness, width ratio, material ductility | AISC 360-22 Table K2.1A, DG 24 Table 8-1A |
| Chord plastification | AISC 360-22 Table K2.1 |
| Chord punching shear | AISC 360-22 Table K2.1 |
| Branch local yielding and effective width | AISC 360-22 Chapter K |
| Gapped K sub-connection capacity | AISC Design Guide 24 Section 9.6 |
| Weld strength | AISC 360-22 J2.4 |
## Reading the results
Governing demand-to-capacity ratios per limit state, with the joint classification stated explicitly.
## Assumptions and exclusions
Joints falling outside the supported applicability limits are flagged as not supported, with warning notes explaining the gap. The sheet does not extrapolate beyond the code limits.
## Related
* [Round HSS longitudinal plate connection](/docs/connections_hub/calculators/round_hss_longitudinal_plate)
* [Round HSS transverse plate connection](/docs/connections_hub/calculators/round_hss_transverse_plate)
**Where you can use this:** [Atlas Tube HSS Connections Hub](https://connectionshub.atlastube.com/login/organisations?src=CALCSDOCS) only
**Status:** Beta · **Region:** US · **Design codes:** AISC 360-22, AISC Design Guide 24 (2nd ed.)