Design of a trussed tower supporting a chimney

✅ Chimney Trussed Tower Design for Auto Crop Care Ltd. – 100 ft Steel Structure on Deep Foundation

Project Location: Mamarishpur, Mollickbari Road, Bhaluka, Mymensingh, Bangladesh
Client: Auto Crop Care Limited
Design by: Ascending Consulting Engineers

🏗️ Project Overview

We are proud to present the structural and foundation design of a 100 ft tall chimney-supporting trussed tower, designed and engineered for Auto Crop Care Ltd. The project required a highly stable and durable structural system to safely support the chimney under critical wind and seismic loads.

The structure consists of a steel trussed tower supported on a cast-in-situ piled foundation system. The foundation includes a robust reinforced concrete pile cap designed to transfer high overturning moments into the deep soil strata.

📐 Design Standards & Materials

The design adheres to the following international and national codes:

• BNBC 2020
• ASCE 7-05
• ASME STS-1-2012
• AISC 360-05
• ACI 318-08

Material Properties:

• Concrete strength: 4000 psi
• Rebar yield strength: 60,000 psi
• Structural steel: ASTM A572 Gr. 42 or higher (Gr. 50 used)

🌪️ Key Structural Design Considerations

• Wind speed: 67.4 m/s — significant overturning moment required a deep foundation system
• Lateral System: Trussed steel members with lateral chimney guides designed to allow thermal movement while ensuring stability
• Serviceability: Wind sway limited to h/100 = 300 mm, satisfying AISC Design Guide 3
• Stability: P-Δ effects and modal behavior evaluated for dynamic stability

🧱 Foundation Design – Why Shallow Was Rejected

The team evaluated the feasibility of a shallow footing system. Here’s why it was not adopted:

• Required footing thickness: 3.30 m (130 in) — extremely thick due to high overturning moment
• Required soil pressure: 19.8 ksf, while allowable capacity was only 5.77 ksf
• High water table at 2.4 m depth complicates deep excavation

🔧 Conclusion: Shallow foundation was structurally and geotechnically unsuitable. A cast-in-situ piled foundation was proposed and adopted.

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• Structural Design