Compressive Strength
Physical load capacity determines the maximum top-to-bottom compressive force a finished corrugated shipping container can withstand before collapsing under pressure. Commonly referred to as bct, this metric is evaluated by compressing an empty carton between two flat, parallel platens in a laboratory test press at a standardized rate of loading. The measurement terminates when the structural integrity of the carton fails, yielding a force value expressed in Newtons.
Mathematical Prediction
Predictive equations such as McKee formula use board caliper, flexural stiffness and short-span compression values to calculate this compression limit without requiring physical assembly. When actual laboratory testing is conducted, moisture content in the paperboard must be controlled because ambient moisture reduces overall board stiffness. Flute geometry and the orientation of the corrugating medium are the primary factors that dictate the final result of the test.
A higher density medium improves the ability of the finished container to resist deformation.
Safety Margin
Real conditions in warehouses deviate from short-term laboratory assessments because of continuous loading over extended durations. Carton stacking patterns and pallet overhang can reduce the effective strength to a fraction of the initial test value. In long-term storage, fatigue and creep lower the load limit.
