> ## 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.
# Anatomy of a Calculation
> How Key Properties, Summary, Bolt Inputs, Applied Loads and the expandable calculations fit together in every Connections Hub sheet.
**Where you can use this:** [Atlas Tube HSS Connections Hub](https://connectionshub.atlastube.com/login/organisations?src=CALCSDOCS) and [Calcs.com](https://app.calcs.com/login?src=calcsdocs)
**Status:** Released
Every connection calculator in the Hub uses the same layout. Learn it once and every other calculator reads the same way.
The 49 minute webinar walk-through covers the same ground in depth, with live examples.
## Key Properties
The top section. Member sizes, material grades, orientation and the connection configuration.
This section is gating. Changing a member size or the connection type can add, remove or reword the inputs below it, so work top to bottom rather than jumping around. Where a calculator supports several configurations (for example conventional versus extended plate, or beam on one side versus two sides), that toggle sits here.
Typical inputs:
* Beam and column or girder HSS sections, and grade (commonly ASTM A500 Grade C or A1085)
* Design method, ASD or LRFD
* Connection type and plate configuration
* Member orientation, rotatable in top and side views to match field conditions
## Plate, weld and bolt inputs
Geometry for the connecting elements.
* Plate thickness, width, length and setback
* Fillet weld size
* Bolt size, grade, thread condition (included or excluded from the shear plane), and whether the joint is slip-critical with its faying surface class
* Vertical and horizontal bolt spacing, and edge distances
Some calculators restrict bolt diameters to those compatible with the Atlas Tube Shuriken blind fastener. Through-bolt presets lift that restriction and open the full ASTM F3125 range, because capacity is then governed by bolt shear rather than a slip-resistance limit state.
## Applied Loads
Add or remove load cases and edit magnitudes. Dead, live, snow, wind and seismic are supported.
You generally have two entry modes:
* **Individual load inputs.** Enter unfactored loads by type and let the sheet generate and sweep the ASCE 7 load combinations. The governing combination is reported per limit state.
* **Pre-factored loads.** Enter demands you have already factored. Faster when your analysis model already produces factored envelopes.
Seismic capacity design is the exception. Where a calculator runs AISC 341-22 checks, it requires individual load inputs so the overstrength combination is applied explicitly, and factored entry is disabled while seismic is active.
## Summary
The live diagram plus the headline result.
The diagram redraws from your geometry, including cope dimensions, plate positions, bolt patterns and member rotation. Treat it as your first check: if it does not look like the connection you are detailing, an input is wrong.
Below it, utilisation is reported as a colour-coded percentage per group, for example:
| Group | What it covers |
| ------------------------- | ------------------------------------------------------------------- |
| Column or girder capacity | Wall slenderness, plastification, punching shear, sidewall yielding |
| Bolt capacity | Shear, bearing, tearout, tension and combined interaction |
| Plate capacity | Yielding, rupture, block shear, flexural and combined interaction |
| Beam capacity | Yielding and rupture, including at a reduced coped section |
| Weld capacity | Directional strength method, eccentric weld group where relevant |
## Expandable calculations
Every limit state expands to show the full working: the equation as written in the code, the substituted values, the result, and the clause reference. This is what makes the output reviewable rather than a black box, and it is what your checker will read.
## Limits of applicability
Most HSS connection provisions only apply within geometric and material bounds, for example the chord slenderness and width ratio limits in AISC 360-22 Table K2.1A and the equivalents in AISC Design Guide 24.
Where a calculator gates on those limits, it says so and suppresses the downstream limit states rather than reporting a result you cannot rely on. An unsupported configuration produces an explicit message, not a silent pass.
## Related
* [Getting started](/docs/connections_hub/getting_started)
* [Exporting reports and details](/docs/connections_hub/exporting_reports_and_details)
**Where you can use this:** [Atlas Tube HSS Connections Hub](https://connectionshub.atlastube.com/login/organisations?src=CALCSDOCS) and [Calcs.com](https://app.calcs.com/login?src=calcsdocs)
**Status:** Released