Futuristic cityscape featuring interconnected polygonal steel structures.

Steel Strong: How to Build Smarter with Polygonal Hollow Sections

Lena Kashyap in Tech & Innovation September 2025 • 4 min read.

"Unlock design secrets and boost structural performance using advanced techniques for polygonal steel poles."

In modern construction, efficiency and aesthetics go hand in hand. Polygonal steel poles, crafted from multi-sided hollow sections, are emerging as a compelling alternative to traditional circular designs. These poles are particularly useful in applications like lighting towers and power lines, where minimizing visual impact and land use is crucial.

The push for more compact designs, especially in power transmission, often leads to specifying thicker-walled sections to maintain structural integrity. However, this can increase costs and negate some of the benefits of compact designs. European design standards offer guidelines, but these sometimes restrict the full potential of polygonal sections by not fully accounting for their plastic behavior—the ability to deform without losing load-bearing capacity.

Recent research is challenging these limitations. By exploring how polygonal sections behave under bending forces, engineers are discovering ways to optimize their designs. This article will delve into the plastic behavior of these structures, comparing experimental data with numerical models to refine design rules and unlock greater efficiency in steel construction.

What Makes Polygonal Hollow Sections Stand Out?

Futuristic cityscape featuring interconnected polygonal steel structures.

Polygonal hollow sections offer a unique blend of structural advantages and design flexibility. Unlike circular sections, which distribute stress uniformly, polygonal sections exhibit varying stress concentrations at their corners and flat sides. This characteristic can be leveraged to enhance bending resistance and optimize material use.

To understand how these sections behave, engineers often treat them as a series of individual plate strips. Each strip is subject to specific buckling criteria, as defined in Eurocode 3 (EC3), a set of European standards for steel structure design. The key parameter in this assessment is the c/t ratio, which relates the width of the plate (c) to its thickness (t). This ratio determines the section's classification, influencing how its load-bearing capacity is calculated.

Class 1 & 2 Sections: Designed to fully utilize plastic reserves, allowing for significant deformation before failure.
Class 3 Sections: Limited to elastic behavior, meaning they can only be stressed up to the yield point.
Class 4 Sections: Susceptible to local buckling, requiring more complex calculations to determine their effective resistance.

The current design rules can sometimes create a sharp drop in allowable stress between Class 2 and Class 3 sections, a phenomenon that doesn't always reflect real-world performance. This has spurred research into refining these classifications to better predict the actual behavior of polygonal sections, especially in bending.

The Future of Polygonal Steel in Construction

The research into polygonal hollow sections is paving the way for more efficient and innovative steel structures. By refining design rules and better understanding the plastic behavior of these sections, engineers can create lighter, stronger, and more cost-effective designs. This is particularly relevant for applications where aesthetics and minimizing environmental impact are key considerations. As construction practices evolve, expect to see more widespread adoption of polygonal steel in a variety of architectural and engineering projects.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

Everything You Need To Know

What are the primary advantages of using Polygonal Hollow Sections in construction compared to traditional circular designs?

Polygonal Hollow Sections offer several advantages over traditional circular designs. They provide a unique blend of structural benefits and design flexibility. Unlike circular sections, which distribute stress uniformly, Polygonal Hollow Sections exhibit varying stress concentrations at their corners and flat sides. This characteristic can enhance bending resistance and optimize material usage. These are particularly useful in applications such as lighting towers and power lines where minimizing visual impact and land use is crucial. They also facilitate more compact designs, leading to efficient and cost-effective structures.

How do engineers determine the load-bearing capacity of Polygonal Hollow Sections, and what role does Eurocode 3 (EC3) play?

Engineers assess the load-bearing capacity of Polygonal Hollow Sections by treating them as a series of individual plate strips. Each strip is then subjected to specific buckling criteria as defined in Eurocode 3 (EC3), the European standard for steel structure design. The c/t ratio, which is the width of the plate (c) to its thickness (t), is a key parameter in this assessment. This ratio determines the section's classification (Class 1 to 4), influencing how the load-bearing capacity is calculated. The standards define the level of plastic behavior and how much deformation is allowable before failure.

What are the key differences between Class 1, Class 2, Class 3, and Class 4 sections in the context of Polygonal Hollow Sections, and how do they impact design?

In the context of Polygonal Hollow Sections, the classifications based on Eurocode 3 (EC3) define the section's behavior under stress. Class 1 and 2 sections are designed to fully utilize plastic reserves, allowing for significant deformation before failure. Class 3 sections are limited to elastic behavior, meaning they can only be stressed up to the yield point, while Class 4 sections are susceptible to local buckling, requiring more complex calculations to determine their effective resistance. The choice of section class influences how engineers calculate the load-bearing capacity, with each class dictating different levels of allowable stress and deformation.

Why is there ongoing research into the plastic behavior of Polygonal Hollow Sections, and what are the potential benefits?

Ongoing research into the plastic behavior of Polygonal Hollow Sections is aimed at refining design rules and unlocking greater efficiency in steel construction. Current design rules can sometimes create a sharp drop in allowable stress between Class 2 and Class 3 sections, a phenomenon that doesn't always reflect real-world performance. By exploring how Polygonal Hollow Sections behave under bending forces, engineers are discovering ways to optimize their designs, potentially leading to lighter, stronger, and more cost-effective structures. This includes a better understanding of how these sections deform without losing their load-bearing capacity.

In what types of construction projects are Polygonal Hollow Sections particularly well-suited, and why are they becoming more prevalent?

Polygonal Hollow Sections are particularly well-suited for applications where aesthetics and minimizing environmental impact are key considerations. These include lighting towers, power lines, and various architectural and engineering projects. Their ability to offer structural advantages while facilitating more compact designs makes them an attractive alternative to traditional circular designs. The push for more efficient and cost-effective structures, coupled with the ongoing research to refine design rules and better understand the plastic behavior of these sections, is driving their increasing prevalence in modern construction practices.