A protective coating-free steel structure spindle-shaped column between high-speed railway lines and its design method

Abstract

This invention relates to the field of steel structure technology, and in particular to a spindle-shaped steel structure column for high-speed railway lines without protective coating and its design method. It includes an inner and outer steel pipes arranged coaxially, with an annular cavity between the inner and outer steel pipes filled with a concrete interlayer. In a non-fire state, the inner and outer steel pipes and the concrete interlayer share the load. In a fire state, the inner steel pipe acts as the load-bearing unit, and the concrete interlayer acts as the fireproof protection layer for the inner steel pipe. The advantages of this invention are: this structure completely avoids the problems of easy aging, powdering, and peeling of fireproof coatings in open-air environments, eliminating the need for regular inspection and recoating, significantly reducing the maintenance cost and workload throughout the entire life cycle; the concrete interlayer serves as a permanent physical fireproof protection layer for the inner steel pipe, with stable and reliable fire resistance performance that will not fail due to environmental erosion or train wind pressure, and it will not release toxic fumes at high temperatures, improving fire evacuation safety.

Description

Technical Field

[0001] This invention relates to the field of steel structure technology, and in particular to a spindle-shaped steel structure column for high-speed railway lines that does not require protective coating and its design method. Background Technology

[0002] Steel structures along high-speed railway lines (such as canopies, overhead contact line supports, and bridge ancillary structures) are typically designed for fire resistance limits according to the "Technical Specification for Fire Protection of Steel Structures." The conventional practice is to spray thick or thin fire-retardant coatings onto the steel components. The coating expands and foams at high temperatures or forms an insulating layer to slow down the temperature rise of the steel, thus meeting the specified fire resistance time requirements and ensuring the structural safety and stability. In addition to fire protection design, corrosion prevention must also be considered for steel structures. Currently, common corrosion prevention designs mainly involve applying anti-corrosion coatings to the surface of the steel structure, often requiring multiple layers of protective coatings.

[0003] However, taking fire-retardant coatings as an example, using fire-retardant materials as protective coatings has obvious drawbacks. For instance, fire-retardant coatings are susceptible to the effects of sun and rain, freeze-thaw cycles, and the airflow from high-speed trains in open-air environments, easily leading to aging, powdering, or peeling, resulting in unreliable fire-retardant performance. Routine maintenance and testing are difficult and costly; after failure, recoating is required, necessitating the removal of the existing old protective coating during the recoating process, which is time-consuming and labor-intensive. Furthermore, some organic intumescent coatings may release toxic fumes at high temperatures, posing additional risks to evacuation and rescue during a fire. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of the prior art by providing a steel structure spindle column between high-speed railway lines that does not require protective coating and its design method. This invention achieves a novel steel structure spindle column design by setting up inner and outer steel pipes with a double-layer structure and pouring a concrete interlayer. This design meets fire protection design requirements while fundamentally eliminating the various defects caused by protective coatings.

[0005] The objective of this invention is achieved through the following technical solutions: A steel structure spindle-shaped column for high-speed rail lines that requires no protective coating is disclosed. This column is narrowed at both ends and has a spindle-shaped body. Its features include: an inner steel pipe and an outer steel pipe arranged coaxially; an annular cavity is left between the inner and outer steel pipes, and a concrete interlayer is filled within the annular cavity; in a non-fire condition, the inner and outer steel pipes and the concrete interlayer share the load; in a fire condition, the inner steel pipe acts as the load-bearing unit, and the concrete interlayer serves as the fireproof protective layer for the inner steel pipe.

[0006] Several threaded steel bars are embedded in the concrete interlayer, and these threaded steel bars are evenly distributed along the inner and outer steel pipes in a staggered manner.

[0007] The inner steel pipe is provided with an inner partition plate with ventilation holes, and the inner partition plate is placed horizontally at the center line of the inner steel pipe along the height direction.

[0008] The outer steel pipe has an internal annular partition.

[0009] The inner steel pipe is made of carbon steel, and the outer steel pipe is made of stainless steel composite steel.

[0010] A design method for the aforementioned protective coating-free steel structure spindle-shaped column between high-speed railway lines, characterized in that the design method includes the following steps: The inner steel pipe is designed to withstand all design loads under fire conditions. The thickness of the concrete interlayer is designed according to the fire resistance rating requirements, and the concrete interlayer is wrapped around the inner steel pipe. The outer steel pipe is designed under normal working conditions where the inner steel pipe, the concrete interlayer, and the outer steel pipe are subjected to stress together.

[0011] When the outer steel pipe is a stainless steel composite pipe, it includes an outer stainless steel layer, which is not included in the strength calculation.

[0012] The advantages of this invention are: 1) This structure completely avoids the problems of fireproof coatings aging, powdering, and peeling in open-air environments, eliminating the need for regular inspections and recoating, and significantly reducing maintenance costs and workload throughout the entire life cycle.

[0013] 2) The concrete interlayer serves as a permanent physical fireproof protection layer for the inner steel pipe. Its fire resistance is stable and reliable, and it will not fail due to environmental erosion or train wind pressure. Moreover, it will not release toxic fumes at high temperatures, thus improving the safety of fire evacuation.

[0014] 3) Through the coordinated stress design of the inner and outer steel pipes and the concrete interlayer, both structural efficiency and fire protection goals of "no protective coating" are achieved.

[0015] 4) The inner and outer partitions and ring partitions enhance the local stability of the components, while the outer steel pipe is made of stainless steel composite steel pipe, the stainless steel layer can provide excellent weather resistance and corrosion resistance, further extending the service life of the structure.

[0016] 5) It achieves durable, safe and low-maintenance design of steel structures between high-speed railway lines. The structure is simple and reasonable, with a wide range of applications. The design method is easy for technicians to implement and is suitable for promotion. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2This is a schematic diagram of the cross-sectional structure of the present invention; Figure 3 This is a schematic diagram of the upper cross-sectional structure of the present invention; Figure 4 This is a schematic diagram of the middle cross-sectional structure of the present invention; Figure 5 This is a schematic diagram of the lower cross-sectional structure of the present invention. Detailed Implementation

[0018] The features and other related features of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments, so as to facilitate understanding by those skilled in the art: like Figure 1-5 As shown in the figure, each of the markings represents: 1. Steel structure spindle column, 2. Stainless steel composite steel pipe, 3. Concrete interlayer, 4. Carbon steel pipe, 5. Grade III threaded steel, 6. Inner partition, 7. Ring partition, 8. Ventilation hole.

[0019] Example: Figure 1 As shown in the figure, the steel structure spindle-shaped column between high-speed railway lines without protective coating in this embodiment is a column that narrows at both ends and has a spindle-shaped body. The width of the column body gradually transitions evenly from both ends to the centerline in the height direction.

[0020] like Figure 2 As shown, the steel structure spindle-shaped column includes an inner steel tube and an outer steel tube arranged coaxially. The inner steel tube is made of carbon steel 4, while the outer steel tube is made of stainless steel composite 2. An annular cavity is left between the carbon steel tube 4 and the stainless steel composite 2, and a concrete interlayer 3 is filled in the annular cavity.

[0021] In non-fire conditions, the stainless steel composite pipe 2, concrete interlayer 3, and carbon steel pipe 4 work together to bear the load, ensuring a stable structural support. In a fire condition, the carbon steel pipe 4 acts as the sole load-bearing unit, while the concrete interlayer 3 serves as a fireproof protective layer. The inner carbon steel pipe 4 is the main load-bearing unit of the entire column during a fire. While the outer stainless steel composite pipe 2 experiences a rapid decrease in strength at high temperatures, it does not rely on the load-bearing capacity. Even if the outer layer fails at high temperatures, the concrete interlayer 3 can still effectively protect the carbon steel pipe 4, ensuring it maintains its load-bearing capacity for a certain period during a fire, preventing sudden collapse of the supporting structure and providing time for evacuation and rescue. Although the initial manufacturing cost is slightly higher than existing technologies that use pure carbon steel pipes coated with a protective layer, this embodiment fundamentally eliminates the need for periodic recoating and repair, and avoids the risk of decreased fire resistance due to coating aging. Therefore, in terms of long-term life-cycle costs, this embodiment can effectively reduce costs compared to existing technologies. At the same time, maintenance work has been further reduced, avoiding frequent additional interference with high-speed rail operations.

[0022] In this embodiment, the stainless steel composite pipe 2 is manufactured by laminating a stainless steel layer onto the outside of a carbon steel pipe, thus solving the problem of anti-corrosion coating for ordinary steel. The outer stainless steel layer is directly exposed to the atmospheric environment, exhibiting excellent weather resistance, salt spray resistance, and industrial corrosion resistance, eliminating the need for any anti-corrosion coating. This completely avoids the hassle of periodic painting and maintenance required for the outer surface of traditional carbon steel, making it particularly suitable for the open-air, difficult-to-maintain conditions along high-speed rail lines. Simultaneously, the smooth and aesthetically pleasing stainless steel surface enhances the landscape quality of the high-speed rail line.

[0023] like Figure 3 , Figure 4 or Figure 5 As shown, several grade III threaded steel bars 5 are embedded in the concrete interlayer 3 at the top, middle and bottom of the steel structure spindle column 1. The grade III threaded steel bars 5 are evenly distributed along the inner and outer steel pipes in a staggered manner, and each grade III threaded steel bar 5 is arranged vertically along the height direction and welded to the inner wall of the stainless steel composite steel pipe 2 or the outer wall of the carbon steel pipe 4. The grade III threaded steel bars 5 embedded in the concrete interlayer 3 are used to improve the bonding performance between the concrete and the steel pipe and improve the overall cooperative stress.

[0024] like Figure 4 As shown, an inner partition 6 with vent holes 8 is provided inside the inner carbon steel pipe 4. The inner partition 6 is placed horizontally at the center line of the carbon steel pipe 4 along the height direction to increase the local structural strength of the steel structure spindle column 1 and solve the problem of a centripetal concentrated force formed at the bend of the steel pipe. The vent holes 8 are used to prevent harmful gases from being trapped inside the steel pipe during the processing and manufacturing of welding.

[0025] like Figure 4 As shown, an annular diaphragm 7 is provided inside the stainless steel composite pipe 2. The position of the annular diaphragm 7 corresponds to the position of the inner diaphragm 6, and the two can be at the same cross-sectional height. This annular diaphragm 7 is used to improve the resistance of the stainless steel composite pipe 2 to local buckling. In some cases, such as... Figure 4 As shown, the ring partition 7 and the grade III threaded steel bar 5 located in the middle are connected and fixed to form an integral structure. Specifically, the grade III threaded steel bar 5 passes through the ring partition 7, which further improves the structural performance at this node position.

[0026] When applied, this embodiment includes the following design method: 1) Calculate the dimensions of carbon steel pipe 4, which serves as the inner steel pipe, under fire conditions: Based on the fire resistance limit requirements and fire resistance rating, the minimum thickness of the concrete interlayer 3 is determined, and a thickness greater than the minimum thickness of the concrete interlayer 3 is selected to meet the fire resistance limit requirements of the carbon steel pipe 4.

[0027] Under fire conditions, only carbon steel pipe 4 is considered to bear the full design load. Based on the design load under fire conditions and the material selected for carbon steel pipe 4, such as the design strength of Q355 steel, the ratio of the outer diameter to the thickness of carbon steel pipe 4 is designed.

[0028] Specifically, the ratio of the outer diameter to the thickness of carbon steel pipe 4 should not exceed 150. ε k 2 =99.3, where ε k It is a dimensionless parameter, and its function is to adjust the limit of the diameter-to-thickness ratio according to the actual yield strength of the selected steel. Its calculation formula is εk = √(235 / fy), where 235 is a reference value, that is, the standard yield strength of Q235 steel, and fy is the yield strength of the steel used in carbon steel pipe 4 in the design.

[0029] Based on the outer diameter and thickness of the designed carbon steel pipe 4, its overall stability bearing capacity is tested; when its overall stability bearing capacity meets the requirement of bearing all design loads under fire conditions, it meets the design requirements.

[0030] 2) Calculate the dimensions of the stainless steel composite steel pipe 2, which serves as the outer steel pipe, under normal operating conditions: The stainless steel composite pipe 2 is decomposed into an inner carbon steel pipe and an outer stainless steel composite layer, wherein the stainless steel composite layer is not included in the strength calculation. Taking the dimensions of the designed carbon steel pipe 4 as a reference, and based on the coaxial relationship between the inner and outer steel pipes, the outer diameter and thickness of the proportionally enlarged stainless steel composite pipe 2 are designed. The design dimensions of the stainless steel composite pipe 2 should be sufficient to reserve a sufficient annular cavity between it and the carbon steel pipe 4 to allow for the pouring space of a concrete interlayer 3 of a certain thickness.

[0031] Under normal working conditions, the carbon steel pipe 4, concrete interlayer 3, and stainless steel composite pipe 2 are subjected to stress together. The overall stability coefficient and section compressive bearing capacity are calculated for each designed structural dimension using intermediate and end sections. When the requirements are met, the design is completed.

[0032] This embodiment addresses the shortcomings of traditional steel pipe coating by proposing an innovative structure of stainless steel composite pipe + carbon steel inner pipe. Concrete is placed between the pipes as a fireproof coating, and the proposed design method solves the fire prevention problem. The stainless steel composite pipe solves the corrosion problem, thus decomposing the protective coating on the steel structure surface into two parts, the inner and outer parts of the pipe, ultimately solving the problem of steel structure protective coating and enabling long-term service of steel columns between high-speed railway lines without protective coating.

[0033] Although the above embodiments have described the concept and embodiments of the present invention in detail with reference to the accompanying drawings, those skilled in the art will recognize that various improvements and modifications can still be made to the present invention without departing from the scope of the claims, and therefore will not be elaborated here.

Claims

1. A steel structure spindle-shaped column for high-speed rail lines that requires no protective coating, wherein the steel structure spindle-shaped column is a column that narrows at both ends and has a spindle-shaped body, characterized in that: The steel structure spindle-shaped column includes an inner steel tube and an outer steel tube arranged coaxially, with an annular cavity between the inner and outer steel tubes and a concrete interlayer filling the annular cavity. In a non-fire state, the inner and outer steel tubes and the concrete interlayer share the load. In a fire state, the inner steel tube acts as the load-bearing unit, and the concrete interlayer acts as the fireproof protection layer for the inner steel tube.

2. The spindle-shaped steel structure column between high-speed railway lines without protective coating as described in claim 1, characterized in that: Several threaded steel bars are embedded in the concrete interlayer, and these threaded steel bars are evenly distributed along the inner and outer steel pipes in a staggered manner.

3. The spindle-shaped steel structure column between high-speed railway lines without protective coating as described in claim 1, characterized in that: The inner steel pipe is provided with an inner partition plate with ventilation holes, and the inner partition plate is placed horizontally at the center line of the inner steel pipe along the height direction.

4. A spindle-shaped steel structure column for high-speed rail lines without protective coating as described in claim 1, characterized in that: The outer steel pipe has an internal annular partition.

5. A spindle-shaped steel structure column for high-speed rail lines without protective coating as described in claim 1, characterized in that: The inner steel pipe is made of carbon steel, and the outer steel pipe is made of stainless steel composite steel.

6. A design method for a spindle-shaped steel structure column between high-speed railway lines without protective coating, as described in any one of claims 1-5, characterized in that: The design method includes the following steps: The inner steel pipe is designed to withstand all design loads under fire conditions. The thickness of the concrete interlayer is designed according to the fire resistance rating requirements, and the concrete interlayer is wrapped around the inner steel pipe. The outer steel pipe is designed under normal working conditions where the inner steel pipe, the concrete interlayer, and the outer steel pipe are subjected to stress together.

7. The design method for a spindle-shaped steel structure between high-speed railway lines without protective coating as described in claim 6, characterized in that: When the outer steel pipe is a stainless steel composite pipe, it includes an outer stainless steel layer, which is not included in the strength calculation.

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