A Comparative Analysis of the Economic Efficiency of Hot-Rolled and Welded H-Beams in Bridge Engineering

A Comparative Analysis of the Economic Efficiency of Hot-Rolled and Welded H-Beams in Bridge Engineering
The selection of structural steel is crucial in the design and construction of bridge projects, directly impacting the overall project cost, structural safety, construction period, and long-term maintenance. As two mainstream steel products, hot-rolled and welded H-beams each have their own advantages and applicable scenarios. This article will provide an in-depth comparison of their economic advantages for bridge engineering, providing a reference for project decision-making.

I. Concept and Process Overview
Hot-rolled H-beams are produced by rolling high-temperature billets through a universal rolling mill in a single pass. They have fixed dimensions and are mass-produced in steel mills, resulting in high dimensional accuracy, high production efficiency, and consistent quality.

Welded H-beams are constructed from three steel plates (two flanges and one web) welded together in the factory or on-site using an automatic submerged arc welding process. Their dimensions can be flexibly customized to meet design requirements and are not restricted by standard catalogs.

II. Multi-Dimensional Comparative Analysis of Economic Efficiency
Economy does not simply refer to the initial purchase price; it encompasses a comprehensive cost concept across the entire lifecycle, encompassing material costs, fabrication and processing costs, construction efficiency, and maintenance costs.

1. Materials and Initial Purchase Costs

Hot-rolled H-beams: Due to large-scale, continuous production, their raw material and manufacturing costs are relatively low. Standard-spec steel sections typically have a lower price per unit weight than welded H-beams of the same specifications. If standard-spec hot-rolled H-beams can be directly used in bridge designs, significant cost advantages can be achieved in material procurement.

Welded H-beams: Their cost structure includes steel plate material costs, cutting, assembly, welding, and flaw detection fees. Due to the numerous manufacturing processes involved, their initial manufacturing costs are typically higher than those of directly purchased hot-rolled products. This cost advantage is particularly weak when steel market prices are high.

Conclusion: Standard-spec hot-rolled H-beams generally offer a competitive advantage in terms of initial purchase costs.

2. Processing and Customization Costs

Hot-rolled H-beams: Fixed specifications offer limited flexibility. If a bridge design requires non-standard dimensions or special cross-sections (such as extra-high or extra-wide H-beams), hot rolling is not feasible and welding is necessary.

Welded H-beams: Their core advantage lies in their extreme flexibility. Cross-sectional dimensions can be optimized based on the bridge's load-bearing characteristics, and different plate thicknesses can be used in different locations (i.e., "variable-section H-beams") to maximize material utilization and minimize steel waste. While the cost per ton is high, design optimization can reduce the overall steel usage in the structure, thereby saving overall costs.

Conclusion: For bridge components with non-standard, unusual shapes, or those requiring optimized cross-sections, welded H-beams, while costly per ton, can achieve better overall economics through structural optimization.

3. Construction and Installation Efficiency

Hot-rolled H-beams: They offer consistent product quality and are ready for use immediately after delivery, eliminating the need for additional production and waiting time. They can be hoisted and installed immediately upon arrival, significantly shortening construction time. This reduced construction time translates to lower indirect costs such as management fees and machinery rental, resulting in significant economic benefits.

Welded H-beams: Require a significant production cycle, especially for large components, placing high demands on the factory's processing capabilities, welding processes, and quality control. If welding is performed on-site, it can be affected by weather and environmental factors, potentially extending the construction period.

Conclusion: Hot-rolled H-beams offer significant advantages in construction efficiency, accelerating project schedules and reducing overall costs.

4. Long-term Maintenance and Durability Costs

Hot-rolled H-beams: As integrally rolled steel, they lack welds and offer improved overall uniformity. When subjected to dynamic loads (such as vehicle traffic), they generally exhibit superior fatigue strength compared to welded components. From a long-term fatigue perspective, they offer greater reliability and relatively lower maintenance costs.

Welded H-beams: The key to quality lies in the weld seam. Improper welding processes can lead to defects such as porosity, slag inclusions, incomplete penetration, and cracks. These defects can become the initiation points of fatigue cracks, impacting the long-term durability and safety of the bridge and potentially increasing subsequent inspection and maintenance costs. Rigorous non-destructive testing is essential to ensure quality.

Conclusion: In terms of long-term fatigue resistance and durability, high-quality hot-rolled H-beams have a slight advantage, but qualified welded H-beams can also meet bridge code requirements.

III. Overall Conclusion and Selection Recommendations
Comparison Dimensions: Hot-rolled H-beams Welded H-beams
Initial Purchase Cost: Low (applicable to standard specifications) High
Customization Flexibility: Poor Very High
Construction Efficiency: High (no processing required, direct installation) Low (requires processing cycle)
Long-Term Fatigue Performance: Excellent (no welds, good integrity) Good (depends on weld quality)
Applicable Scenarios: Standard components such as main beams, secondary beams, and supports for standard-span bridges; Long-span, variable-section beams, non-standard dimensions, and reinforced joints.
The final economic choice should be based on the specific bridge design:

Preferential Selection of Hot-Rolled H-Beams: When standard steel specifications can be used for the bridge design and their cross-sectional properties fully meet mechanical requirements, hot-rolled H-beams should be preferred. This is the most economical, efficient, and reliable option.

Choosing welded H-beams: Despite the higher initial cost, welded H-beams offer superior overall economic benefits in the following situations:

The required cross-sectional dimensions exceed the national standard for hot-rolled H-beams.

Designed as a variable-section beam, requiring flexible adjustment of flange or web thickness to optimize material distribution.

Used for local reinforcement of joints or specialized structural areas.

In short, when deciding on steel for bridge construction, one should not simply compare unit prices in isolation but instead conduct a full lifecycle comparison of hot-rolled and welded H-beams, comprehensively considering all aspects of design, procurement, construction, and maintenance to make an informed choice that best meets the project's overall economic and technical requirements.