Landing Gear Load Path & Frame Reinforcement

Engineering study on how landing gear transmits loads into the trailer frame — analyzing stress paths, reinforcement layouts, and welding design for long-term durability.

Structural Load Path Frame Reinforcement
📅 Published on 2025-11-10 | ✍️ Semi Trailer News Engineering Desk

Image: Finite element stress map of landing gear attachment zone showing vertical and shear load flow

🔹 Load Path Explained

Landing gear supports the full trailer front weight when uncoupled. Each leg typically carries **8–12 tons**, and the forces flow from the foot plate → leg tube → mounting bracket → cross-member → main beam web. The integrity of this path defines whether the trailer remains level or develops cracks after repetitive loading.

⚙ Common Failure Modes

• Web cracking near landing gear brackets due to high vertical shear.
• Bracket detachment from thin web or incomplete welds.
• Cross-member deformation from asymmetric landing on uneven ground.

📊 Design Recommendations

Parameter	Recommended Practice	Effect
Mounting plate thickness	≥ 8 mm (S355)	Reduces stress at bolt holes
Bracket spacing	≥ 500 mm	Improves stability under lateral load
Cross-member type	Box or tubular	Distributes compression evenly
Weld type	Full fillet both sides	Prevents tear-out under vertical impact

🏗 Reinforcement Strategies

• Add **doubler plates** (5–6 mm) along the inner web around the mounting area.
• Extend reinforcement at least 200 mm beyond the bracket ends to reduce stress gradient.
• Connect both legs with a **torsion beam** to share load and prevent frame twisting.
• Use **stiffening ribs** or vertical gussets if the cross-member is thin.

💡 Industry Practices

Heavy-duty trailer builders such as Faymonville and Nooteboom integrate **modular landing gear support frames** directly into the gooseneck section. This method channels the loads through multiple welded planes instead of a single web, significantly improving fatigue resistance.

🧭 Simulation & Testing

FEA results indicate that the **highest stress concentration** occurs at the lower weld toe of the mounting plate. Reinforcing this area with a 6 mm inner doubler reduces stress peaks by ~30%, and extending the plate below the cross-member further stabilizes the structure.

🧾 Maintenance Tips

• After uncoupling, always ensure the ground surface is even — uneven load splits increase twist.
• Inspect welds at the mounting plate and lower cross-member every 20,000 km.
• If cracks appear, replace the bracket and perform re-welding with preheating to avoid brittle zones.

Conclusion:
Landing gear mounts endure more stress cycles than almost any other chassis point. Proper load path design, full weld penetration, and web reinforcement transform this vulnerable area into a durable structural zone — essential for every trailer’s long life.

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