Principle revealed: Why can prestressed steel strands withstand thousands of tons of pressure?

Prestressed steel strands are made of three factors: material strengthening, structural optimization, and prestressing technology. This allows a small steel strand to withstand thousands of tons of pressure. This technology enables modern buildings to break through the limits of span, height, and durability. There are mainly the following reasons why a steel strand can withstand thousands of tons of pressure:

Material characteristics:

- High-strength steel: Steel strands are usually made of high-quality steel such as high-carbon steel. This special alloy steel (tensile strength of 1860MPa, 4-6 times that of ordinary steel bars) has undergone special heat treatment and cold processing, and has high strength and hardness, and can withstand large tensile forces. For example, a single steel strand with a diameter of 15.2mm can withstand a tensile force of about 26 tons.

- Alloy element strengthening: During the production process of pc steel strands, alloy elements such as chromium, silicon, and vanadium are added. These elements can further improve the strength, toughness and corrosion resistance of steel and enhance the bearing capacity of steel strands.

Structural design:

- Multi-strand twisted structure: The steel strand is made of 7 (or more) steel wires twisted in a spiral. This structure can disperse the stress when the steel strand is under pressure, avoid the single point break of a single steel wire due to excessive local stress, and improve the overall bearing capacity. At the same time, the twisted structure improves the flexibility of the steel strand, so that it can better adapt to various stress conditions in different application scenarios.

- Lay distance optimization: Reasonable design of the lay pitch of the pc steel strand, that is, the distance the steel wire moves forward when it rotates around the axis of the steel strand, can make the contact pressure between the strands of steel wire evenly distributed, improve the density and stability of the steel strand, and further enhance its compressive resistance.

Processing technology：

- Prestressing treatment: During the production process of pc steel strands, they will be prestressed. By pre-applying tension, prestress is generated inside the steel strands. When the structure is under pressure or bending, the retraction force of the steel strands will actively offset the external tension, prevent concrete cracking, delay the deformation and damage of the steel strands, and improve their compressive strength.

- Surface treatment: Surface treatments such as galvanizing and plastic coating on pc steel strands can not only prevent rust and corrosion of pc steel strands, but also improve their surface hardness and smoothness to a certain extent, ensure stability under long-term loads, reduce stress concentration caused by surface friction during force, and enable pc steel strands to withstand pressure more evenly.

A single prestressed steel strand can bear tens of tons of weight. In practical applications, multiple strands are arranged in parallel. For example, hundreds of strands are often used in bridge construction to work together to achieve a bearing capacity of thousands of tons. The prestress is transmitted to the concrete through anchors, forming an efficient combination of "strand tension + concrete compression", maximizing the use of material performance. For this reason, pc steel strands can bear thousands of tons of pressure and easily support the "steel bones" of modern buildings.