How RHS Steel Beams Are Used in Bridge Construction
27 February 2026
When it comes to building bridges, Rectangular Hollow Section (RHS) steel beams are the beams you need. It's their combination of structural efficiency, versatility, and practical benefits that makes them ideal for bridge construction.
From primary load-bearing elements to safety barriers, these hollow rectangular profiles are engineers’ friends. Here’s why.
Understanding the Building Regulations Framework for Structural Steelwork
RHS steel beams are so popular because of their exceptional strength-to-weight ratio. These beams have impressive structural integrity whilst minimising self-weight, which is crucial in bridge construction where reducing dead load allows for longer spans and less demanding foundation requirements. The enclosed rectangular profile has outstanding torsional resistance compared to open sections like I-beams, effectively counteracting the twisting forces that bridges must withstand.
This combination of high performance with reduced weight has some important practical benefits. Transportation costs are lower, crane requirements are reduced, and site assembly is quicker, all contributing to more economical project delivery. The rectangular shape efficiently distributes loads throughout the structure, enhancing overall stability and performance under varying traffic and environmental conditions.
Primary Load-Bearing Applications: Main Girders and Cross Beams
RHS steel beams excel as primary structural elements in bridge construction, used as main girders and cross beams that support the bridge deck. Their rigid rectangular form makes them particularly effective for structures such as flyovers, where they efficiently handle gravity loads from traffic in a single direction.
The flat top surface of RHS beams is an ideal interface for attaching and supporting bridge decks, simplifying construction details and ensuring reliable load transfer. This configuration is widely used in medium-span bridges where the strength and stiffness of RHS sections can be fully utilised.
Tubular Trusses and Arches are Efficient Solutions for Curved Bridge Structures
Truss bridges offer very stiff, lightweight solutions with minimum structural depth, and RHS beams are particularly well-suited for forming tubular trusses and arches in curved bridge applications.
The hollow rectangular sections can be configured into triangulated frameworks that act efficiently in tension and compression, creating structures that are both visually appealing and structurally efficient.
Tubular steel truss bridge designs provide attractive and lightweight solutions, making them ideal for spans where aesthetic considerations are important alongside structural performance. This approach is used in footbridges, canal crossings, and architectural bridge designs.
Lateral Stability and Bracing: Essential Support Systems
RHS steel beams provide lateral stability and resist wind and other horizontal forces in bridge structures. When used as bracing members in truss configurations, the enclosed rectangular profile offers superior rigidity compared to open sections, helping to prevent unwanted movement and ensuring the bridge stays stable under varying load conditions.
The flat sides of RHS sections facilitate straightforward bolted and welded connections to main structural elements, allowing bracing systems to be installed efficiently whilst maintaining the required structural capacity throughout the bridge's service life.
Practical Construction Benefits: Ease of Fabrication and Assembly
The flat sides of RHS steel beams simplify fabrication and site assembly processes, making both welded and bolted connections more straightforward compared to circular or open sections. This cuts construction time and labour costs whilst keeping connection quality and structural integrity.
The hollow design makes these beams lighter than their solid counterparts, making them easier to transport and install. Additionally, RHS sections are used for safety features such as guard rails and barriers, where their strength, durability, and clean lines provide both functional performance and visual appeal along the bridge’s structure.
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