Cable Containment Support Calculator
Lay out an interconnected support network — threaded rods and Unistrut channels hung from a rib-deck soffit — and check every rod, fixing and bearer to BS 8519:2020. Loads roll up automatically; export an auditable, formula-visible Excel calculation.
This is a desktop tool — on a small screen you can view and edit through the table and panel, but the diagram works best with a mouse.
This tool is a design aid for cable-containment support engineering to BS 8519:2020. The exported spreadsheet — with its visible formulas — is the record of calculation, and every value marked VERIFY must be confirmed against current manufacturer literature before a calculation is issued. Loading assumptions, fixing capacities and site conditions remain the responsibility of the design engineer.
What This Calculator Does
Cable containment — trunking, tray, basket and ladder — is typically suspended from the soffit on threaded rods and Unistrut channels. On a real riser or plant deck these supports form an interconnected network, not independent trapezes: channels hang from rods, rods hang from other channels, some rods are shared between two bearers, and everything accumulates upward to a handful of ceiling fixings. This tool lets you draw that network, rolls the loads up automatically, and checks every element against capacity.
The Five Checks
For each fire/service condition (ambient, 30, 60 or 120 minutes) the calculator checks: rod tension against the reduced allowable stresses of BS 8519:2020 Table E.1; top fixings (Lindapter VN wedge nuts in rib deck) against their fire-tested capacities; channel bending against manufacturer simple-beam safe working loads using the equivalent-UDL method; channel nuts against slip capacity; and a load-conservation sanity check that catches support shares that don't sum to one.
Why Fire Cases Govern
At ambient temperature a threaded rod works at around 100 N/mm² — but in a 120-minute fire case BS 8519 reduces that to just 6 N/mm², and a wedge-nut fixing that holds 2.1 kN cold may be rated at only 0.4 kN. A bracket that passes comfortably at ambient can fail badly in fire, which is why the condition switch re-checks the whole network instantly — and why fire-rated services that must survive (alarm, evacuation, firefighting circuits) deserve their own check with all services still hanging on the shared supports.
An Auditable Excel Record
The headline feature: Export Excel writes a workbook where every computed cell contains a live formula — load roll-ups reference each child element's cells, so a checker can follow the entire load path with Excel's Trace Precedents, flip the fire condition inside the spreadsheet, and watch every PASS/FAIL recompute. Reference tables, sources and a VERIFY register are included, because a calculation that feeds a stamped package must be checkable, not a screenshot.