In recent years, the construction of large-span cable bridges in China has grown from scratch and achieved good results, and the construction technology of long-span suspension bridges, cable-stayed bridges, and arch bridges is at an international leading level. For example, the main span of the Xihoumen Bridge is 1650m, ranking second in the world; the Taizhou Bridge surpasses the suspension bridge by a span of 2000m with a 2 × 1080m three-tower two-span. At the same time, China's bridge cables have to be imported from the beginning of wire rods and steel wire materials, and gradually realized the localization of wire rods and steel wires. Until now, the export of cables has provided a solid foundation for China to become a big and powerful country in cable bridge technology. Guarantee.
In order to meet the growing traffic needs of our country, cable bridges are continuing to develop. Since there is no other material to replace, high-strength steel wires, steel strands, and steel ropes are still the basic raw materials for large-span bridge cable structures. The comprehensive performance and output requirements of the steel wire and its products are continuously improved, and the special-shaped steel wire is also gradually used in the bridge cable structure. It has a good application prospect in the bridge cable structure, but it is subject to small processing batches and processing costs. Higher restrictions. The application of special-shaped steel wire in bridge cable structure mainly includes S-shaped steel wire and Z-shaped steel wire. At present, China's S-shaped steel wire can be processed in batches and applied to the main cable winding of suspension bridges. Z-shaped steel wire and other special-shaped steel wire sealing wire ropes also have special standards in China, but there is no similar product used in bridge cables.
China's special-shaped steel wire production started late, and enterprises do not pay enough attention
Special-shaped steel wire mainly refers to non-circular cross-section steel wire, which is different from round steel wire in name. The characteristic of special-shaped steel wire is that the cross-sectional shape of the steel wire is more complicated, the dimensional accuracy requirements are higher, and the shape meets special needs, and no further cutting is required. The production of round steel wire mainly adopts drawing processing, the process is relatively simple, and the production efficiency is high; the production of special-shaped steel wire requires the use of special molds to process a variety of steel wires of different shapes through drawing, rolling, or combination of drawing and rolling. It is complicated and the production efficiency is relatively low.
Relevant data shows that the production of special-shaped steel wire is small, the production difficulty is difficult, the quality is difficult to control, and the value and benefit are not obvious. Therefore, it has not been valued by professional manufacturers. Due to the late start, China's production enterprises have adopted a combination of special die drawing, rolling and drawing. Although they have been able to produce a variety of shapes of special-shaped steel wire, the shape, size, tolerance, strip performance, appearance and surface treatment of the steel wire are There is still a certain gap between China and foreign advanced technology. Therefore, most of the high-quality special-shaped steel wires used in high-end products in China still mainly rely on imports, such as oval steel wires for car valve springs. In recent years, due to the needs of China's national economic development, the production of profiled steel wire has begun to receive attention and development in China.
Among them, the S-shaped steel wire in the special-shaped steel wire is mainly used for the main cable to protect the winding and improve the sealing protection function of the main cable; the Z-shaped steel wire is mainly used to manufacture and process the sealed steel wire rope, which is mainly used for passenger ropeway and mine hoist , Tower crane main cable, excavator stretch rope, large construction cable, etc. Some foreign countries use this kind of sealed steel wire rope for suspension bridge main cable, sling, cable-stayed bridge cable and arch bridge sling cable structure.
S-shaped steel wire has become one of the application directions of the main cable winding of suspension bridges
Cables are important structural parts of cable bridges. The main cables of suspension bridges are generally considered as non-replaceable structural parts. Although cables, slings, etc. can be replaced, the replacement cost is high and affects traffic. Therefore, the safety of bridge cables is long-term. And protection has always been the focus and problem of bridge structure research. From the end of the 20th century to the beginning of the 21st century, Japan applied S-shaped steel wire instead of round steel wire to the winding of the main cable, and increased the dehumidification protection of the main cable. It achieved good protection effect and was generally recognized by the industry.
The advantages of the S-shaped steel wire winding of the main cable of the suspension bridge over the traditional round steel wire winding are: S-shaped steel wire is used as the main cable winding wire. After winding, the steel wires are pressed together as one, the sealing effect is good, and it can effectively block the condensation of rain and sea fog. Water intrusion reduces the corrosion of the main cable of the suspension bridge by acidic medium and prolongs the service life of the main cable of the suspension bridge; at the same time, the S-shaped tangent wire and the surface coating or other protection methods cooperate to form an airtight protective layer outside the main cable, so that the main cable The dehumidification system is basically guaranteed.
At the same time, from the perspective of the construction of suspension bridges at home and abroad in recent years, the S-shaped steel wire has become one of the development directions for the winding protection of the main cables of newly built suspension bridges.
In recent years, many steel wire manufacturing enterprises in China have considered the research and trial production of S-shaped steel wire, but due to more problems, they have not been put into formal production. Starting from the Taizhou Bridge, the domestic S-shaped steel wire and the main cable dehumidification system began to be localized. Jiangsu Faersheng Cable Co., Ltd. took the lead in researching, developing and processing the S-shaped steel wire. In the past two years, the domestic S-shaped steel wire has been in the Taizhou Bridge (main span 2 × 1080m), Nanjing Fourth Bridge (main span l418m) and Maanshan Bridge (main span 2 × 1080m) are the main cable protection winding applications of 3 well-known suspension bridges.
With the popularization and application of the domestic S-shaped steel wire main cable winding, not only the S-shaped steel wire special molds and equipment have been developed and applied, but also promoted the progress of the S-shaped steel wire processing technology. Moreover, after the S-shaped steel wire is galvanized, the shaping process is added to ensure S-shaped steel wire processing shape and size deviation meet the technical requirements.
Performance and application of Z-shaped steel wire rope
Z-shaped steel wire is also a special-shaped steel wire, and the processing method is similar to other special-shaped steel wire. Z-shaped steel wire rope is a special single-twisted steel wire rope, which is made of ordinary single-twisted round steel wire rope as the core and is wrapped with one or more layers of Z-shaped steel wire. Other special-shaped steel wires (X-shaped, T-shaped, etc.) can also be twisted in this way. Compared with the special single-twisted steel wire rope of round steel wire, this special-shaped steel wire has a compact structure, smooth surface, no rotation, good sealing, but poor flexibility. Z-shaped steel wire ropes are mainly used in some large-scale hoisting equipment, mine shaft lifts, overhead ropeways and building bridge cables.
â— Pros and cons of Z-shaped steel wire rope
The performance advantages of Z-shaped steel wire ropes are: First, the density coefficient is greater than 0.9. Compared with ordinary steel ropes of the same diameter, the total breaking tension is about 65% higher; Second, the entire steel wire rope is approximately a round bar. The support surface is large, the pressure per unit area is small when used, the stress distribution is relatively uniform, and the service life is long; third, the surface is sealed, the outside air and water are not easy to penetrate into the steel wire rope, the surface is smooth, it is easy to increase the protective layer, and the interior The anti-rust material is not easy to be lost, which prevents the corrosion of the internal steel wire. Fourth, the twist length is large, the structure elongation is small, and the adjacent layers of steel wire are twisted in opposite directions and have good non-rotation.
However, this kind of special-shaped wire rope also has disadvantages. First of all, the flexibility of the steel wire rope is very poor, can not be bent on a smaller radius, must use a larger diameter rope wheel and reel. Secondly, the tooling of this kind of steel wire processing equipment is relatively complicated and the manufacturing cost is relatively high. Therefore, the application range of this type of steel wire rope is limited. Domestic Z-shaped steel wire and other special-shaped steel wire sealing steel wire ropes have not been applied to cable bridges.
Industry experts pointed out that the performance characteristics of the Z-shaped steel wire sealing wire rope are more suitable for the cable structure and can be easily processed into cable strands. The Z-shaped steel wire processing of the two sections of the sealed steel wire rope is matched with the anchor, which is relatively easy to process into cable strands. The characteristics of sealing, anti-corrosion, axial stiffness, and no torsion make Z-shaped steel wire ropes suitable for bridge cable structure applications. Z-shaped steel wire ropes are widely used in foreign bridge cables, mainly cable bridge sling structures and small diagonals Pull the bridge.
â— Application of Z-shaped steel wire sealing steel wire rope in bridge cable structure
Since the diameter of the Z-shaped steel wire sealing wire rope is between 20mm and 70mm, the load-bearing structure of the cable stays and slings applied to it is limited. In recent years, data show that Z-shaped steel wire ropes are used in small and medium-sized arch bridges, cable-stayed bridges, and suspension bridges. The following describes two applications of Z-shaped steel wire ropes in main cable strands and slings of suspension bridges.
The main cable of the French Aquintin Suspension Bridge. The French Aquintin Suspension Bridge is a three-span suspension bridge with a span of 143m + 394m + 143m. The main cable is composed of 37 Z-shaped steel wire sealing steel wire rope strands, each of which has a diameter of 72.6mm and 6 layers of 127 diameters of 4.1 mm steel wire, two layers of 4.5mm Z-shaped steel wire sealing outer layer, the minimum breaking force of each strand is 4450kN. In the early 21st century, the bridge was overhauled to increase the passage, and the main cable replacement was composed of 61 sealed steel wire strands, of which 55 strands have a diameter of 60mm and 6 strands have a diameter of 42mm. The replaced strands are sealed steel wire ropes or semi-sealed steel wire ropes (the outer layer is not a single twisted round stranded steel wire rope with a Z-shaped steel wire). Belt and main cable dehumidification protection.
Sling of Hardanger Bridge, Norway. The Hardanger Bridge in Norway is a large-span suspension bridge that spans the Hardanger Strait in southwestern Norway. The total length of the bridge is 1380m, the main span is 1310m, and the width of the stiffening beam is 17.7m. The bridge has a total of 130 slings and the sling bridge The horizontal spacing is 20m and the lateral spacing is 14.5m. A single sling is set for each lifting point, and the length of the sling gradually changes from 2.04m to 127.6m. Except for the 5 short slings on each side of the span using rigid ropes, all other The Z-shaped steel wire is used to seal the steel wire rope strands. The section of the sling is composed of 7 layers of steel wire, and the outermost 3 layers are Z-shaped steel wires to achieve the sealing of the steel wire strands and play a role in anti-corrosion. The sling is connected to the main cable and the steel box main beam by a 160mm pin hinge.
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