Hot-dip pure zinc (Z)
In the hot-dip pure zinc process, the zinc content in the molten pool must be no less than 99%. Pure zinc coatings can produce spangles of varying sizes. While these spangles affect the surface appearance, they do not affect corrosion resistance.

Hot-dip galvanized aluminum (ZA)
The molten metal in the molten pool contains approximately 5% aluminum (Al) and a small amount of rare earth elements, with the remainder being zinc. Zn-Al coatings have a brighter surface and offer greater corrosion resistance than pure zinc coatings, but are less commonly used in China.

Hot-dip aluminum silicon (AS)
The molten metal in the molten pool contains approximately 8% to 11% silicon (Si), with the remainder being aluminum. Al-Si coatings form a distinct aluminum-iron-silicon alloy layer on the steel surface. They offer excellent high-temperature resistance, making them suitable for high-temperature processing and operating environments. Hot-dip Al-Si coated steel sheets and strip are a type of "aluminum-coated sheet" referred to in the trade.

Hot-dip galvanized magnesium (ZM) coatings, also known as zinc-aluminum-magnesium (ZAM), consist of a molten metal pool composed of aluminum and magnesium, typically 1.5-8% combined (at least 0.2% magnesium is required), with the remainder being zinc. This coating offers exceptionally good overall corrosion resistance, particularly for shear fracture protection.

Based on their structural load characteristics, steel structures can be divided into the following categories:

Gateway Frame Structure:This type of structure is a traditional structural system, with the upper main structure consisting of inclined beams, columns, braces, purlins, ties, and gable frames. Portal frame structures offer simple load-carrying mechanisms, clear force transmission paths, and are easily prefabricated, resulting in rapid construction. They are widely used in industrial, commercial, and cultural and entertainment buildings. This system originated in the United States and, after nearly a century of development, has developed a mature set of design, manufacturing, and construction standards.

Space truss structures, also known as ball-joint trusses, are lightweight, high-strength, spatially rigid structures constructed in a geometrically modular form. They utilize tension and compression rods to coordinate forces in three dimensions, offering excellent multi-directional load-bearing capabilities and making them particularly suitable for public buildings with large spans and high seismic requirements.

Beam-string structures, systematically proposed by Japanese scholar Professor M. Saitoh, are a hybrid roof system combining a rigid upper chord, flexible cables, and central struts. This structure utilizes a self-balancing mechanism to achieve long-span prestressed spatial loads, leveraging the advantages of both rigid and flexible materials. It boasts simple construction, balanced load distribution, and easy construction, and has broad application prospects.

Susp-dome structures: Similar to beam-string structures, both utilize cable tension to reduce the burden on the main structure. However, suspend-dome structures utilize a circular tensioning system, making them more suitable for circular or near-circular roof structures, such as those in the Beijing Velodrome and Anhui University Gymnasium.

Grid Structure:This type of structure consists of numerous members connected by nodes in a regular pattern. The nodes are often hinged. The members are primarily axially loaded, resulting in small cross-sections and high material efficiency. Its strong regularity facilitates standardized production and on-site installation, making it an efficient long-span spatial structural system.

Multi-story Structure

Frame Structure: Columns and beams form the main framework, carrying vertical and lateral loads. It has low lateral stiffness and large lateral displacement, and is generally used in buildings under 20 stories. Columns often use box sections or concrete-filled steel tubes. The latter combines the advantages of steel and concrete, offering high load-bearing capacity and good seismic resistance.

Frame-Shear Wall Structure: Shear walls replace braces to carry lateral forces. Concrete walls, steel plates, or a combination of these structures can be used. This system offers high lateral stiffness and flexible layout, making it suitable for taller buildings.

Tube-in-Tube Structure: An inner core tube and an outer frame tube or truss tube typically work together to resist horizontal forces. A solid-web tube is a tube enclosed by shear walls, which forms a framed tube after openings are made. A trussed tube is composed of vertical and diagonal members. This structure offers high rigidity and is suitable for supertall buildings.

A bundled-tube structure is composed of multiple tubes, which utilize a modular grid layout to enhance overall rigidity and lateral resistance. It offers strong architectural adaptability and a rich visual appeal. A typical example is the Sears Tower in Chicago.

A steel structure building is a load-bearing structure constructed from basic components made of steel sections or steel plates, welded or bolted together to form a regular, load-bearing structure. This type of structure is widely used in a variety of applications, including steel bridges, industrial plants, gates, large pipelines and containers, public buildings, and high-rise buildings.