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Vigorously promote the use of H-shaped steel. H-shaped steel is an economical structural section with a cross-sectional shape similar to the uppercase Latin letter H; it is also known as universal steel beam, wide-flange I-beam, or parallel-flange I-beam. It differs from the hot-rolled I-beams that have been in use in China for a long time, characterized by narrower flanges and inclined inner surfaces. The difference in cross-sectional shape between H-shaped steel and ordinary I-beam is shown in the figure. The cross-section of an H-shaped steel is typically divided into a web and flanges, also known as the core and edges. The inner and outer sides of an H-shaped steel are parallel or nearly parallel to each other, and the ends of the sides form right angles; hence it is called a parallel-sided I-beam. Compared to ordinary I-beams that have the same height at the waist section, H-beams have a thinner waist section and wider flanges; hence they are also known as wide-flange I-beams. Due to its geometric properties, the section modulus, moment of inertia, and corresponding strength of H-shaped steel are significantly superior to those of ordinary I-beams with the same weight. In practical engineering, the I-shaped cross-section is the most commonly used. However, I-beams have a narrow width and poor load-bearing capacity. In contrast, H-beams, which have a cross-section similar to that of I-beams, feature a more rational and superior shape; they represent an ideal type of economical cross-sectional profile for use in engineering applications. Based on the loading characteristics during use, hot-rolled H-beams are divided into three series: beams, columns, and piles. In terms of applications in steel structure projects, the former is suitable for bending members such as steel beams, while the column series is suitable for compressive members such as steel columns; the latter is intended for construction of building foundations. Hot-rolled H-beams are steel materials with an excellent cross-sectional distribution and a better strength-to-weight ratio. Compared with ordinary I-beams, hot-rolled H-beams have the following notable product features: ① The inner and outer surfaces of the flanges are parallel, and the end faces of the flanges are straight, which facilitates mechanical processing, structural connection, and installation ； ②It has a wide flange and high lateral stiffness, and its moment of inertia about the weak axis is generally more than twice as large ； ③It has strong bending, compressive, and torsional resistance, with an increase of generally 5–10% ； ④The range of model specifications is more than twice that of I-beams, which greatly facilitates design selection and optimization. H-shaped steel is used in metal structures with various requirements, and it demonstrates excellent performance when subjected to bending moments, compressive loads, or eccentric loads. It can enhance the load-bearing capacity compared to ordinary I-beams. Moreover, due to its wide flanges, thin web, a variety of specifications, and flexibility in use, it allows for a reduction of metal usage by 10–40%. Since its inner and outer edges are parallel to each other and the edge ends form right angles, it is easy to assemble them into various components, thereby reducing welding and riveting work by about 25%; this allows for an **acceleration of the construction process and a reduction in project duration. Due to the aforementioned advantages, H-shaped steel is widely used, covering all applications of ordinary I-beams. Mainly used for: various industrial and civil building structures ； Various large-span industrial buildings and modern high-rise buildings, especially those in areas with frequent earthquakes and in industrial facilities where high temperatures prevail ； Large bridges that require high load-bearing capacity, good cross-sectional stability, and large spans ； Heavy equipment ； highway ； Ship skeleton ； Mine support ； Foundation treatment and dam engineering ； Various mechanical components. At present, reinforced concrete and brick-concrete structures are still widely used in construction projects in our country. The large amount of concrete blocks that end up being discarded cannot be recycled or decomposed, and from a long-term perspective, this type of construction method causes significant damage to the ecological environment. As the primary structural material in building structures, hot-rolled H-beams enjoy the reputation of being \"green building materials\" in the field of building steel structures, as the material can be fully recycled and reused, resulting in minimal environmental impact. H-shaped steel structures can effectively overcome the disadvantages of reinforced concrete structures, such as heavy weight and large structural dimensions, while also improving the ductility of the structure and enhancing its seismic performance. Steel structure buildings that use hot-rolled H-shaped steel as the main structural material are constructed with steel beams and columns produced in factories as their framework, along with new types of lightweight insulation, heat-insulating, and high-strength wall materials used as the enclosure structure. It has advantages such as high strength, large span, low self-weight, good lateral resistance, small structural cross-sectional dimensions, and a short construction period; these features enable an improved utilization rate of the building area and higher economic benefits. (The technical and economic comparison of three structural options – steel structure, composite structure, and reinforced concrete structure – conducted during the design of the Shanghai Hilton Hotel showed that the self-weight of the steel structure is 60% lower than that of the reinforced concrete structure, the usable area is 6% larger in the case of the steel structure, and the construction speed is nearly 50% faster for the steel structure.) H-shaped steel has the following significant advantages in use: ① H-shaped steel can reduce the weight of structural components in buildings and similar structures by 15–30%, and when used in bridges, it can reduce the weight of such components by 13–15% ； ②With the same load, using H-shaped steel can reduce the amount of steel required ； ③Using H-shaped steel to construct buildings or structures can reduce the construction time by half compared to using reinforced concrete, and it also minimizes the impact of construction on the surrounding environment ； ④When constructing buildings of the same area, using H-shaped steel allows for an increase in the usable area by about 6% compared to using reinforced concrete. It also enables a reduction in the height of beams at the same span, thus allowing for lower floor heights while maintaining the same clear height; this results in a reduction of approximately 3% in the workload related to interior and exterior walls ； ⑤H-shaped steel can be split, cut, and assembled to form T-shaped steel and honeycomb beams. Using these in place of ordinary steel shapes such as I-beams, angles, and channels for constructing roof trusses and supports can save a significant amount of material and reduce the weight of the structure ； ⑥The dynamic load resistance of H-shaped steel is **higher than that of welded H-shaped steel and reinforced concrete; it possesses excellent seismic and typhoon resistance, making it more suitable for constructing high-rise buildings, industrial facilities, and long-span bridges ； ⑦Hot-rolled H-beams are formed using universal rolling mills, resulting in sections with accurate and straight dimensions. Since they eliminate the welding and straightening processes required for welded H-beams, they can save costs by approximately 15–30%. Therefore, structural design using H-shaped steel as the main material for steel structures is considered by industry experts to be the future development trend. There are many product specifications for H-beams, which can be classified as follows: ① Based on the width of the beam’s edges, they are divided into wide-edge, medium-edge, and narrow-edge H-beams. For wide-flange H-beams, the flange width b is greater than or equal to the web height h; for medium-flange H-beams, the flange width b is greater than or equal to half of the web height h; for narrow-flange H-beams, the flange width b is equal to or less than half of the web height h. ②Classified by application, they include H-shaped steel beams, H-shaped steel columns, H-shaped steel piles, and thick-walled H-shaped steel beams. Sometimes parallel-leg channel steel and parallel-edge I-beams are also included in H-beams. Narrow-flange H-beams are generally used as beam members, while wide-flange H-beams are used as column members. Therefore, it is also known as beam-type H-beam and column-type H-beam. ③Based on the production method, they are divided into welded H-beams and rolled H-beams. ④H-beams are classified into large, medium, and small sizes according to their dimensions. Products with a waist height of 700 mm or more are generally referred to as large size, those with a waist height of 300–700 mm are called medium size, and those with a waist height of less than 300 mm are classified as small size. Internationally, the product standards for H-beams are divided into two main categories: the imperial system and the metric system. Countries such as the United States and the United Kingdom use the imperial system, while countries like China, Japan, Germany, and Russia use the metric system. Although the imperial and metric systems use different units of measurement, H-beams are generally specified using four dimensions: web height h, web thickness d, flange width b, and flange thickness t. Different countries use various methods to specify the dimensions of H-beams, but the range of dimensions and dimensional tolerances of the products manufactured remain fairly similar. H-shaped steel can be produced either by hot rolling or by a combination of welding methods. Welding H-beams involves cutting steel strips of appropriate thickness into the right width, and then welding together their edges and web on a continuous welding machine. Welding H-shaped steel has disadvantages such as high metal consumption, low economic efficiency in production, and difficulty in ensuring uniform product performance. Therefore, the production of H-shaped steel relies mainly on rolling. The main difference in rolling between H-shaped steel and ordinary I-beam steel is that the latter can be rolled in a two-roller die, while the former requires a universal die. Hot-rolled H-beams produced by using near-net-shape continuous casting billets and a four-roller universal rolling process possess significant advantages such as high quality, high efficiency, low energy consumption, and low costs; they offer great benefits in terms of improving the quality of steel materials and enhancing economic efficiency in their use. For a long time, H-beam products have been manufactured using a method in which the inner width of the web remains constant when the specifications change. Recently, Japan has developed H-beams with a fixed outer width, which makes the connection of steel structural members even more convenient. In addition, lightweight thin-walled H-beams and some H-beams with special cross-sectional shapes are also favored by the market. In terms of steel types, in addition to H-beams used for general structures, weather-resistant, high-strength welded, stainless steel, fire-resistant, and coated H-beams have also been developed. It can be said that as technology continues to advance, the variety and specifications of H-shaped steel are increasing, and its quality is becoming better. Vigorously promoting the use of H-shaped steel to replace conventional I-beams can help save steel consumption, with the key technology being the use of universal rolling mills.