Container Lashing & Stack Load Tool

Stack Weight • Vertical Compression • Ship Acceleration • Transverse Shear • Twistlocks • Lashing Rods • Wind • CSM / Lashing Software Screen

Container Lashing & Stack Load Tool

Screen a deck-container stack using actual container weights and ship-specific securing limits. Simple mode checks total stack compression and transverse securing demand. Advanced works tier by tier, carrying the weight and inertia of every container above each interface and comparing those demands with user-entered CSM/class limits for vertical compression, twistlock shear/tension and lashing-rod capacity.

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Need tier-by-tier weights, twistlock limits and rod angles? Click Advanced above.Simple uses an average-weight stack and nominal summed securing capacity. The ship’s approved lashing computer and Cargo Securing Manual remain controlling.

StackVertical compression load

TransverseInertia + wind restraint

LashingsRod & twistlock margin

Stack & Design Accelerations

Number of container tiers

Average gross weight per containertonnes.

Container heightm.

Transverse design accelerationg, user-entered ship/route/position basis.

Vertical dynamic acceleration magnitudeg. Compression factor = 1 + az.

Transverse wind pressurekPa on exposed stack side area.

Exposed side area per tierm².

Entered Securing Limits

Permissible bottom stack compressionkN, from CSM/class/lashing software.

Total twistlock transverse shear allowancekN across bottom interface.

Active lashing rods

Lashing angle from horizontaldegrees.

Allowable tension per rodkN from approved securing basis.

Stack / Voyage Design Basis

Transverse acceleration ayg.

Longitudinal acceleration axg.

Vertical dynamic acceleration magnitude azg. Downward compression uses 1+az; uplift screen uses 1−az.

Container external widthm.

Transverse wind pressurekPa.

Additional dynamic / operational factor1.00 if entered accelerations already contain the approved dynamic basis.

Tier / Interface Register

Tier 1 is the bottom container. Interface limits entered on each row apply immediately below that tier, carrying that tier and every active tier above it. All allowable loads must come from the ship’s approved Cargo Securing Manual, lashing software, class documentation or certified equipment data.

Use	Gross wt t	Max gross t	Height m	Exposed side area m²	Permissible vertical compression kN	Twistlock shear allowance kN	Twistlock tension allowance kN	Racking screen limit kN	Lashing rods	Rod angle ° from horiz.	Rod allowable kN each

Container Securing Checks

Approved Cargo Securing Manual checkedStack location, permissible stack weights and lashing pattern match the approved CSM. Approved lashing software / class basis checkedAcceleration and allowable-force inputs match the ship’s approved calculation basis. Actual container gross weights verifiedTier weights come from the final stow/VGM basis, not estimates. Container CSC / max gross limits checkedNo unit exceeds its certified maximum gross mass. Twistlocks / lashing rods correct typeBottom, intermediate and automatic/semi-automatic equipment match the CSM arrangement. Lashing gear condition checkedPortable and fixed fittings are inspected, maintained and certified as required. Weather / route basis reviewedExpected voyage conditions and any approved weather-dependent lashing basis are appropriate. Heavy-over-light stow reviewedWeight distribution has been checked in the approved lashing calculation, especially high tiers.

Critical limitation: this is not approved container lashing software. It uses a simplified static load-path screen and cannot reproduce class-specific nonlinear 3D lashing calculations, twistlock clearances, hatch-cover/lashing-bridge deformation, container-frame flexibility, dynamic contact forces or exact rod/twistlock force sharing. The approved Cargo Securing Manual and approved lashing software remain controlling.

Current framework: IMO’s CSS Code requires cargo to be stowed and secured so the ship and persons are not put at risk, with securing planned for the most severe weather expected on the voyage and in accordance with the Cargo Securing Manual. IACS UR C6 and C7 add harmonized lashing-software and container-securing-system requirements for dedicated container ships contracted for construction on or after 1 July 2025. UR C6 Rev.1 is scheduled to enter into force on 1 January 2027.

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