Choose the tipping edge
Use the same physical edge and moment reference for every input.
CRANE & SITE / TOOL 22
Gantry Overturning Moment Calculator
Organize restoring and overturning actions about one selected tipping edge in a gantry assessment.
Before you start: required inputs
- Mark the tipping edge on the arrangement drawing before measuring any lever arm.
- List the relevant masses, their horizontal offsets, horizontal forces, force heights and any additional moment for one assessed load case.
Calculation diagram
A PRACTICAL WALKTHROUGH
How to use this calculator
Separate the actions
Put masses on the restoring side in the restoring term. Put masses outside the edge and destabilizing horizontal actions in the overturning terms.
Compare the moments
Read the restoring moment, overturning moment and their ratio. Repeat for other edges and required load cases.
One entered tipping-edge case
THE INPUTS
60,000 kg restoring mass at 4 m, 35 kN horizontal action at 12 m, and 5,000 kg outside the edge at 2 m; no other moment.
THE RESULT
Restoring moment is 2,353.596 kN·m and overturning moment is 518.067 kN·m. The arithmetic moment ratio is about 4.543.
What does the result mean?
01
The ratio compares only the actions entered for this one edge and load case.
02
An algebraic balance above zero means the entered restoring moment exceeds the entered overturning moment; it is not a design acceptance.
03
Dynamics, acceleration, wind combinations, clamps, anchorage and uplift resistance require the appropriate separate model.
Watch for this
Measuring the restoring arm from the gantry centre while measuring the horizontal force height from the rail, so the moments do not share one reference.
Formula & model conditions +
M_restoring = m_restoring × g × arm / 1,000
M_overturning = F_horizontal × height + m_outside × g × arm_outside / 1,000 + M_other
Moment ratio = M_restoring / M_overturning
- All lever arms are perpendicular distances to the same selected tipping edge.
- Entered masses and horizontal force are unfactored static inputs. Loads on the restoring side belong in restoring mass; loads outside the edge belong in outside mass.
- No allowance for dynamics, acceleration, rail clamps, anchorage, uplift restraint or specified load combinations. The ratio is an arithmetic moment ratio, not a stability acceptance factor.
Common questions
What moment ratio is required?
Acceptance depends on the applicable design method, factored load combinations and restraint arrangement. This tool deliberately assigns no universal threshold.
What if there is no overturning action?
The tool reports “No overturning action” instead of an infinite ratio. That statement applies only to the entered case.