Dynamic Strain Rate Modeling for Multi Ply Boxboard under Rapid Compression
Dynamic strain rate modeling predicts multi-ply boxboard Z-direction compression and interlayer shear collapse during high-speed converting and package drops.
BCT Safety Factor
Design Multiplier
Structural design calculations for corrugated shipping containers require a multiplier to bridge the difference between laboratory test conditions and real-world warehouse stresses. The bct safety factor compensates for the progressive loss of compression strength that occurs during distribution and storage. This coefficient ensures that the finished case can withstand sustained loading under imperfect conditions.
Degradation Variable
Stacking boxes on pallets introduces misalignments that reduce the load-bearing capacity of the bottom case. Fluctuations in relative humidity cause the moisture content of the paperboard to rise, which accelerates the creep behavior of the cellulose fibres and diminishes the bct safety factor over time. When pallets are stacked up to three high in a warehouse, the static load must be borne by the lowest carton for weeks or months.
Poor pallet patterns, such as column stacking or interlocking arrangements, further diminish the effective strength of the corrugated structure.
Calculation Ratio
Applying the correct coefficient determines the target box compression strength that must be achieved during manufacturing. A standard calculation starts with the actual weight of the stack above the bottom box and multiplies this force by the bct safety factor to yield the target value. Typical values range from three to five depending on the severity of the expected logistics chain.
Over-specifying this value leads to excessive board weight, while under-specifying it risks carton collapse.