The Unistrut trapeze is bowing under a heavy duct run
A bowed trapeze means the support is overloaded, undersized, or spanning too far. Do not leave the duct hanging on a deflected support; verify the load and upgrade the support method.
Do not ignore a sagging trapeze or try to hide the bow by raising one side of the rods.
Check
Measure the duct size, span between rods, and where the strut is bowing.
Check whether the duct is double-wall, lined, heavy gauge, wet/outdoor, or carrying extra load from another trade.
Look for rods pulling out of plumb, anchors moving, insulation crushed, or joints dipping.
Compare the support setup against the approved hanger/support detail.
Temporarily support or unload the condition if there is a risk of failure.
Steps
Measure the duct size, span between rods, and where the strut is bowing.
Check whether the duct is double-wall, lined, heavy gauge, wet/outdoor, or carrying extra load from another trade.
Look for rods pulling out of plumb, anchors moving, insulation crushed, or joints dipping.
Compare the support setup against the approved hanger/support detail.
Temporarily support or unload the condition if there is a risk of failure.
Say this to your foreman
The trapeze under this [duct size/type] is bowing at [location]. I checked the span and added load. Do you want heavier strut, another rod/support point, closer spacing, or an engineered support detail?