Semi-fabricated composite column for intelligent monitoring and construction method thereof

Abstract

The invention provides a semi-fabricated combination column for intelligent monitoring and a construction method of the semi-fabricated combination column. The semi-fabricated combination column comprises an intelligent UHPC-FRP corrugated pipe prefabricated formwork and a core concrete column, wherein the core concrete column is post-poured in the intelligent UHPC-FRP corrugated pipe prefabricated formwork; the intelligent UHPC-FRP corrugated pipe prefabricated formwork comprises a self-sensing UHPC pipe and an intelligent sensing FRP corrugated pipe, and the self-sensing UHPC pipe and the intelligent sensing FRP corrugated pipe are poured into a whole with the intelligent sensing FRP corrugated pipe as an inner formwork. The self-sensing UHPC tube has a self-sensing function and is used for monitoring internal structure health information of the UHPC tube in real time so as to realize intelligent monitoring and maintenance; the intelligent sensing FRP corrugated pipe serves as a formwork inner wall material and is used for monitoring health information between the intelligent UHPC-FRP corrugated pipe prefabricated formwork and an internal core column in real time, and data support is provided for structural health monitoring. The reliability and the safety of the combination column can be enhanced through double intelligent monitoring of the self-sensing UHPC and the intelligent sensing FRP corrugated pipe, and the combination column becomes an important part of intelligent and sustainable development.

Description

Technical Field

[0001] The present invention belongs to the field of civil engineering composite structures, and particularly relates to a semi-precast composite column for intelligent monitoring and its construction method. Background Art

[0002] As a new and favored structural form, composite columns have been widely used in the field of civil engineering due to their excellent load-bearing performance and adaptability. Common forms of composite columns include steel tube-concrete composite columns, FRP tube-concrete composite columns, FRP tube-steel tube-concrete composite columns, FRP tube-concrete-steel tube hollow composite columns, and structural forms such as ECC (engineered cementitious composite)-concrete composite columns and UHPC (ultra-high performance concrete)-concrete composite columns developed in recent years.

[0003] Although the existing composite column technology has significantly improved the structural performance, it still faces serious challenges in harsh environments such as coastal building structures. (1) Corrosion problem: In the coastal environment, chloride attack is the main threat faced by composite columns. Placing the steel tube directly on the outer side of the column as a restraint element can provide good load-bearing capacity, but it is vulnerable to corrosion, resulting in a significant degradation of the structural performance. As an alternative material, FRP tubes have better corrosion resistance, but their mechanical properties and interfacial bond with the core column still show significant degradation when exposed to corrosive solutions or extreme temperatures for a long time. Therefore, using only steel tubes or FRP tubes alone is difficult to meet the requirements of the marine environment for structural durability. (2) Insufficient restraint: ECC materials are used for the outer protective layer of the column due to their excellent ductility, but their restraint on the core column is limited and it is difficult to significantly improve the overall performance of the column. Due to its dense microstructure and extremely high compressive strength, UHPC materials can, to a certain extent, hinder the intrusion of chloride ions, but their restraint ability on the core column is still insufficient, and failure modes such as formwork cracking and debonding are likely to occur, affecting the overall structural performance. (3) Construction difficulty: The construction period of coastal buildings is long and the environment is complex. Using traditional steel formwork for on-site casting not only has corrosion problems, increasing maintenance and construction costs, but also requires frequent erection and demolition, seriously affecting the construction progress. Prefabricated structures have become an important direction for dealing with complex construction environments due to their high construction efficiency and quality controllability. (4) Insufficient monitoring technology: Composite columns are usually applied in marine environments far from land, which poses a huge challenge to structural health monitoring. Traditional structural monitoring means are difficult to achieve real-time and remote monitoring. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide, in view of the above deficiencies of the existing technologies, a semi-precast composite column for intelligent monitoring with good durability, strong anti-lateral deformation ability, high construction efficiency and real-time monitoring function, and its construction method.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is as follows: The present invention first provides a semi-precast composite column for intelligent monitoring, including an intelligent UHPC-FRP corrugated pipe precast formwork and a core concrete column cast later in the intelligent UHPC-FRP corrugated pipe precast formwork; the intelligent UHPC-FRP corrugated pipe precast formwork is prefabricated and formed in a factory, and the intelligent UHPC-FRP corrugated pipe precast formwork includes a self-sensing UHPC pipe and an intelligent sensing FRP corrugated pipe. The self-sensing UHPC pipe is cast integrally with the intelligent sensing FRP corrugated pipe with the intelligent sensing FRP corrugated pipe as the inner formwork. The self-sensing UHPC pipe is used to improve the durability of the intelligent sensing FRP corrugated pipe and the internal core concrete column. The high strength of the self-sensing UHPC pipe is combined with the high confinement ability of the intelligent sensing FRP corrugated pipe to improve the anti-lateral deformation ability of the core concrete column; the self-sensing UHPC pipe has a self-sensing function and is used to monitor the internal structural health information of the UHPC pipe in real time to realize intelligent monitoring and maintenance; the intelligent sensing FRP corrugated pipe is used as the inner wall material of the formwork and is used to monitor the health information between the intelligent UHPC-FRP corrugated pipe precast formwork and the internal core column in real time, providing data support for structural health monitoring.

[0006] A semi-precast composite column of an UHPC-FRP corrugated pipe precast formwork for intelligent monitoring provided by the present invention. The intelligent UHPC-FRP corrugated pipe precast formwork is prefabricated and formed in a factory. The self-sensing UHPC pipe is located outside the intelligent sensing FRP corrugated pipe, and the intelligent sensing FRP corrugated pipe is located on the inner wall of the self-sensing UHPC pipe and can act as the inner wall formwork of the formwork; the intelligent UHPC-FRP corrugated pipe precast formwork includes at least two segments, and the two segments are wet-connected through FRP pipe socket joints, threaded joints embedded in the UHPC pipe, and grouting; the internal core concrete column includes cast concrete and tied steel reinforcement cages; the self-sensing UHPC material and the intelligent sensing FRP corrugated pipe have self-sensing functions and can monitor the structural health information such as the internal stress changes and crack development of the formwork and the column body in real time, providing feedback data to realize intelligent monitoring and maintenance.

[0007] The intelligent UHPC-FRP corrugated pipe formwork can act as a formwork during the casting process of the composite column and jointly bear the load with the core column during the service process of the composite column; the formwork composed of the self-sensing UHPC and the intelligent sensing FRP corrugated pipe can effectively prevent the direct damage of the harsh environment to the FRP corrugated pipe and the internal core column, improving the durability of the composite column.

[0008] The intelligent sensing FRP corrugated pipe is circular, with corrugated structures on both the inner and outer sides, and can form good interfacial bonding with the external self-sensing UHPC and the internal concrete, improving the overall performance of the composite column.

[0009] Self-sensing UHPC materials have self-sensing capabilities, which can monitor the stress changes, crack development and other potential damage of the structure in real time during use, provide real-time feedback, and promptly discover and solve potential problems.

[0010] Self-sensing UHPC is a smart material formed by integrating conductive fillers into the UHPC matrix, which senses stress and strain through changes in resistivity.

[0011] The conductive network of self-sensing UHPC can cause significant changes in resistivity under slight stress changes, thereby achieving highly sensitive perception of stress and strain.

[0012] The cross-sectional dimensions of the self-sensing UHPC-FRP corrugated pipe prefabricated shell can be adjusted according to specific needs, and the thickness of the self-sensing UHPC pipe is between 30 and 100 mm.

[0013] The intelligent sensing FRP corrugated pipe can sense the impact of the mold shell constraint load through the built-in sensor and transmit the information to the monitoring system to achieve intelligent maintenance.

[0014] The self-sensing UHPC in the smart UHPC-FRP corrugated pipe prefabricated shell needs to be added with fiber material to enhance its cracking performance and toughness, and the fiber used is smart fiber.

[0015] The types of smart materials used in the self-sensing UHPC tube of the smart UHPC-FRP corrugated pipe precast shell include self-sensing materials such as carbon fiber, carbon nanotubes or graphene.

[0016] The fiber used in the intelligent sensing FRP corrugated pipe of the intelligent UHPC-FRP corrugated pipe prefabricated shell can be one of carbon fiber, glass fiber or basalt fiber, and the resin polymer used can be one of epoxy resin, vinyl resin or phenolic resin.

[0017] The sensor used in the intelligent sensing FRP bellows of the intelligent UHPC-FRP bellows prefabricated shell is one of the optical fiber, resistor, and strain sensor, and the sensor is woven into one with the fiber.

[0018] The intelligent UHPC-FRP corrugated pipe prefabricated shell includes an upper socket end and a lower spigot end. The FRP corrugated pipe at the upper socket end is flush with the UHPC pipe, and the FRP corrugated pipe at the lower spigot end protrudes 15 to 30 cm from the UHPC pipe.

[0019] The UHPC pipe at the socket end of the intelligent UHPC-FRP corrugated pipe precast formwork is embedded with a stainless steel threaded pipe groove, and at the same time, a grouting sealing groove and a grouting hole are reserved, and the grouting hole communicates with the grouting sealing groove; the UHPC pipe at the spigot end of the UHPC-FRP corrugated pipe precast formwork is embedded with a stainless steel threaded pipe plug, and the stainless steel threaded pipe plug protrudes 15-30 cm from the UHPC pipe, and a slurry outlet hole and a splicing gap are reserved, and the slurry outlet hole communicates with the splicing gap.

[0020] The present invention also provides a construction method for a semi-precast composite column, including: Pouring a self-sensing UHPC pipe with the intelligent sensing FRP corrugated pipe as the inner formwork to form an intelligent UHPC-FRP corrugated pipe precast formwork; Using the intelligent UHPC-FRP corrugated pipe precast formwork as the formwork to pour the core concrete column.

[0021] When constructing the semi-precast composite column of the intelligent UHPC-FRP corrugated pipe precast formwork, insert the FRP threaded pipe at the socket of the upper pipe section into the FRP threaded pipe at the spigot of the lower pipe section; at the same time, insert the stainless steel threaded plug embedded in the UHPC pipe at the socket of the upper pipe section into the stainless steel threaded pipe groove reserved in the UHPC pipe at the spigot of the lower pipe section, and tighten it along the thread; then grout from the grouting hole into the grouting sealing groove until slurry is seen emerging from the slurry outlet hole, indicating sufficient grouting. The grouting material used is a high-strength non-shrinking grouting material; after the formwork support is completed, place a well-bound steel reinforcement cage inside and pour concrete to complete the pouring of the composite column. From the above technical solutions, it can be seen that the present invention has the following advantages:

[0022] A semi - prefabricated composite column with a UHPC - FRP corrugated pipe precast formwork for intelligent monitoring proposed by the present invention combines high - strength self - sensing UHPC with excellent durability and lightweight high - performance intelligent sensing FRP corrugated pipes to form an intelligent precast formwork for assembled construction, and a normal concrete column is poured inside. The self - sensing UHPC material, due to its dense microstructure and strong impermeability, can effectively prevent the intrusion of harmful substances such as chloride ions, delay the corrosion process, and significantly improve the durability of the composite column in harsh marine environments. The self - sensing functional material in the self - sensing UHPC has good conductivity and crack resistance, which can not only provide feedback when the structural load changes, but also give an alarm when cracks or damages occur, helping to achieve structural health monitoring. The intelligent sensing FRP corrugated pipe not only performs excellently in corrosion resistance and high - strength confinement ability, but its intelligent sensing function also significantly improves the stress monitoring ability between the formwork and the core column, enabling the stress condition jointly borne by the UHPC - FRP corrugated pipe formwork and the concrete core column to be monitored in real - time. The intelligent UHPC - FRP corrugated pipe formwork can also provide strong lateral confinement for the core concrete column, effectively suppressing the deformation of the core column under high pressure, thus greatly improving the comprehensive mechanical performance of the composite column, especially showing excellent performance under dynamic loads such as earthquake resistance. In addition, the design of using precast UHPC - FRP corrugated pipe formwork avoids the complex erection and disassembly of traditional steel formwork during construction, especially solves the rust problem faced by traditional steel formwork in marine environments. The application of precast formwork makes on - site construction no longer rely on the cumbersome formwork manufacturing process, greatly simplifying the construction process. At the same time, the semi - prefabricated construction method improves construction efficiency, can significantly shorten the overall construction period, and enhances the controllability and safety of the construction process. The close combination of the dense microstructure in the self - sensing UHPC pipe and the intelligent material ensures the synchronous stability of the mechanical properties and self - sensing properties of the material during long - term use, reducing the maintenance cost and frequency.

[0023] In summary, by combining self-sensing UHPC with intelligent sensing FRP corrugated pipes, the present invention gives full play to the advantages of both, breaks through the limitations of the durability and monitoring difficulties of traditional composite columns, and solves problems such as corrosion resistance, structural performance degradation, and untimely health monitoring commonly found in coastal environments. By providing high-strength lateral restraint and excellent durability, the present invention enables the composite column to not only work stably in harsh environments for a long time but also cope with extreme loads, thus ensuring the long-term safety and stability of the structure. In addition, by adding self-sensing materials to UHPC and embedding intelligent sensors in FRP, the present invention not only provides new technical support for the health monitoring of composite columns but also promotes the development of projects such as intelligent buildings and smart cities. Through the intelligent UHPC-FRP corrugated pipe precast formwork, the composite column can possess the functions of "self-sensing" and "self-repair", greatly improving safety and economic benefits. At the same time, the composite column of the present invention can also achieve fast and efficient construction during the construction process. Based on the above excellent comprehensive performance, the composite column of the present invention has broad prospects and important engineering value in the application of coastal buildings and other harsh environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of a semi-precast composite column of a UHPC-FRP corrugated pipe precast formwork cylinder for intelligent monitoring; Figure 2 Schematic diagram of an intelligent sensing FRP corrugated pipe; Figure 3 Enlarged schematic diagram of the A-A section of the intelligent sensing FRP corrugated pipe; Figure 4 Schematic diagram of a stainless steel threaded plug; Figure 5 Schematic diagram of a stainless steel threaded pipe groove; Figure 6 Schematic diagram of the splicing of the intelligent UHPC-FRP corrugated pipe precast formwork cylinder; Figure 7 Detail schematic diagram of the joint of the intelligent UHPC-FRP corrugated pipe precast formwork cylinder; Figure 8 Schematic diagram of the internal steel reinforcement cage binding; Figure 9 Schematic diagram of the tensile / compressive resistance behavior of self-sensing UHPC under monotonic tension / compression; Figure 10 Schematic diagram of an intelligent monitoring system.

[0025] Among them: 1 is a self-sensing UHPC tube; 2 is a smart sensing FRP corrugated pipe; 3 is the socket end of the smart sensing FRP corrugated pipe; 4 is the spigot end of the smart sensing FRP corrugated pipe; 5 is a stainless steel threaded pipe plug; 6 is a stainless steel threaded pipe groove; 7 is a socket grouting seal groove; 8 is a spigot grouting seal groove; 9 is a slurry outlet hole; 10 is a grouting hole; 11 is longitudinal reinforcement; 12 is stirrups; 13 is concrete; 14 is a smart fiber; 15 is a self-sensing material; 16 is an outer wall thread; 17 is an inner wall thread; 18 is the upper section of the precast formwork; 19 is the lower section of the precast formwork; 20 is an FRP corrugated pipe; 21 is a sensor; 22 is a signal transmitter; 23 is a signal receiver (Bluetooth); 24 is a data storage center; 25 is a computer, 4-1 is the spigot end of the FRP corrugated pipe of the lower section of the precast formwork; 6-1 is the stainless steel threaded pipe groove of the lower section of the precast formwork; 8-1 is the spigot grouting seal groove of the lower section of the precast formwork; 10-1 is the grouting hole of the lower section of the precast formwork. Detailed implementation manners

[0026] The following Figures 1 to 7 further elaborates in detail on the specific implementation manners of the present invention. It should be understood that these implementation manners are only used to illustrate the present invention and not to limit the scope of the present invention. After reading the present invention, various equivalent modifications made by those skilled in the art to the present invention fall within the scope defined by the appended claims of this application. The experimental methods used in the embodiments of the present invention are all conventional methods unless otherwise specified; the materials used in the embodiments of the present invention can all be obtained from commercial channels unless otherwise specified.

[0027] Specifically, as Figures 1 to 7 shown, a semi-precast composite column of a UHPC-FRP corrugated pipe precast formwork for intelligent monitoring, the precast formwork is composed of a smart sensing FRP corrugated pipe 2 and a self-sensing UHPC pipe 1, the core column is composed of concrete 13, longitudinal reinforcement 11 and stirrups 12, and both ends of the smart sensing FRP corrugated pipe are provided with an FRP corrugated pipe socket end 3 and an FRP corrugated pipe spigot end 4. The self-sensing UHPC pipe at the socket end of the smart sensing FRP corrugated pipe is provided with a buried stainless steel threaded pipe plug 5, a grouting hole 9, and a socket grouting seal groove 7. The self-sensing UHPC pipe at the spigot end of the smart sensing FRP corrugated pipe is provided with a buried stainless steel threaded pipe groove 6, a slurry outlet hole 10, and a spigot grouting seal groove 8, as Figure 1 shown.

[0028] In the embodiment of the present invention, the intelligent UHPC-FRP corrugated pipe formwork is prefabricated in the factory. When prefabricating, the intelligent sensing FRP corrugated pipe 2 can be used as the inner formwork during the casting of the self-sensing UHPC pipe 1. The outer formwork of the self-sensing UHPC pipe can adopt formworks made of wood, steel, or polyvinyl chloride. The intelligent UHPC-FRP corrugated pipe formwork can act as a formwork during the casting process of the composite column, and jointly bear the load with the core column during the service process of the composite column, providing high-strength restraint and high durability.

[0029] The FRP corrugated pipe is circular, with corrugated structures both inside and outside, and can form good interfacial bonding with the external self-sensing UHPC layer and the internal concrete, improving the overall performance of the composite column. The combination of the high strength of the self-sensing UHPC pipe 1 and the high restraint ability of the intelligent sensing FRP corrugated pipe 2 significantly improves the anti-lateral deformation ability of the column, and further enhances the seismic resistance, flexural resistance, and crack resistance of the column.

[0030] The thickness of the intelligent sensing FRP corrugated pipe is between 10 and 20 mm. The fiber used in the intelligent sensing FRP corrugated pipe can be one of carbon fiber, glass fiber, or basalt fiber, and the resin polymer used can be one of epoxy resin, vinyl resin, or phenolic resin. The sensor used in the intelligent sensing FRP corrugated pipe is one of optical fiber, resistor, or strain sensor, and the sensor is woven into one body with the FRP fiber.

[0031] The thickness of the self-sensing UHPC pipe is 30 to 100 mm. The water-binder ratio of the self-sensing UHPC pipe 1 is controlled between 0.2 and 0.25, the average powder particle size is less than 20 μm, and the average aggregate particle size is less than 1.5 mm. The cement slurry of the self-sensing UHPC pipe 1 is prepared by mixing the following raw materials in parts by weight: 1 part of cement, 0.25 to 0.3 part of silica fume, 1.1 to 1.2 parts of sand, 0.3 to 0.4 part of mineral powder, 0.02 to 0.04 part of high-range water reducer, and 0.2 to 0.25 part of water.

[0032] The self-sensing material used in the self-sensing UHPC includes conductive fibers, which enhance the cracking performance and toughness of the UHPC and also have conductive properties. The conductive fibers used are carbon nanotubes (CNTs), steel fibers, and carbon fibers. Among them, the diameters of the carbon nanotubes (CNTs), steel fibers, and carbon fibers are between 0.2 and 0.5 mm, and the lengths are between 5 and 30 mm. In order to construct a complete conductive network, the volume fraction of the conductive fibers is between 1.0% and 3.0%.

[0033] In order to obtain better conductive performance and higher sensitivity of the self-sensing UHPC, one or more functional fillers can also be added to the self-sensing material used in the self-sensing UHPC. The functional fillers include graphene, polypyrrole, polyaniline, etc. The volume fraction of the functional materials is between 0.1% and 1.0%.

[0034] In the embodiment of the present invention, the intelligent sensing FRP corrugated pipe has a smooth surface without corrugations near both ends, and the upper and lower ends are respectively a socket end 4 and a spigot end 3. The diameter of the socket end 4 is slightly larger than that of the spigot end 3. Figure 2 As shown; the socket end 4 is flush with the self-sensing UHPC pipe, and the plug end 3 protrudes 15 to 30 cm from the UHPC pipe.

[0035] In the embodiment of the present invention, when preparing the prefabricated formwork of the intelligent UHPC-FRP corrugated pipe, a stainless steel threaded pipe plug 5 is pre-embedded in the self-sensing UHPC pipe at the socket end. Figure 3 As shown, the pipe is provided with an outer wall thread 14; a stainless steel threaded pipe groove 6 is embedded in the self-sensing UHPC pipe at the socket end, as shown Figure 4 As shown, the pipe groove is provided with an inner wall thread 15, such as Figure 4 shown.

[0036] In the embodiment of the present invention, a socket grouting sealing groove 7 is arranged close to the stainless steel threaded pipe plug 5, the socket grouting sealing groove 7 is connected around the prefabricated formwork, a slurry outlet hole 9 is arranged at the top of the socket grouting sealing groove, and four slurry outlet holes are evenly arranged around the prefabricated formwork; a socket grouting sealing groove 8 is arranged close to the stainless steel threaded pipe groove 6, the socket grouting sealing groove 8 is connected around the prefabricated formwork, a pipe grouting hole 10 is arranged at the top of the socket grouting sealing groove, and six grouting holes are evenly arranged around the prefabricated formwork.

[0037] In the embodiment of the present invention, the smart UHPC-FRP corrugated pipe prefabricated shell includes at least two sections, such as Figure 5 and Figure 6 As shown, when the precast formwork is assembled, the socket end 3 of the FRP corrugated pipe of the upper segment 16 of the precast formwork is inserted into the socket end 4-1 of the FRP corrugated pipe of the precast formwork segment 17; at the same time, the stainless steel threaded pipe plug 5 of the upper segment 16 of the precast formwork is inserted into the stainless steel thread groove 6-1 of the precast formwork segment 17 and tightened along the thread. At this time, the socket grouting sealing groove 7 of the upper segment 16 of the precast formwork and the socket grouting sealing groove 8-1 of the lower segment 17 of the precast formwork are aligned; then, high-strength non-shrinkage grouting material is poured into the grouting hole 10-1 at the socket end of the lower segment 17 of the precast formwork, and the grouting material fully flows into the sealing groove. When slurry flows out from the slurry outlet 10 at the socket end of the upper segment of the precast formwork, it means that the grouting has been fully completed.

[0038] In the embodiment of the present invention, the longitudinal reinforcement 11 and the stirrups 12 are tied together to form a steel cage. Figure 7 As shown; the tied steel cage is placed into the prefabricated intelligent UHPC-FRP corrugated pipe formwork, and concrete is poured. The composite column is obtained after curing in the natural environment for 28 days.

[0039] In the embodiments of the present invention, self-sensing UHPC realizes corresponding functions by embedding the changes in the resistance of self-sensing functional materials such as graphene, polypyrrole, and polyaniline. The resistivity of these materials will change with the changes in external conditions (such as stress, temperature, humidity, etc.). Among them, temperature and humidity will cause expansion and contraction stresses in UHPC. Therefore, the method of setting sensors (such as electrodes, ammeters, voltmeters) in the embodiments of the present invention can be used to directly detect the change in the resistance of the material to obtain corresponding signals. Subsequently, the signal will send the monitoring data to the central processing unit or monitoring platform via a wireless or wired transmission system (such as Bluetooth, Wi-Fi, sensor network). Finally, by processing and analyzing the received data, the purpose of real-time monitoring, damage identification, and health assessment of the concrete structure can be achieved. The process is as Figure 10 shown.

[0040] In the embodiments of the present invention, self-sensing ultra-high performance concrete belongs to the category of multiphase and multi-scale composite semiconductors. The structural characteristics of the self-sensing functional materials inside the self-sensing ultra-high performance concrete are discrete conductive phases (covering conductive fibers and functional fillers), and the conductive phases are randomly distributed in the insulating matrix (the UHPC matrix composed of hydration products and cement clinker).

[0041] In the embodiments of the present invention, the geometric contact and overlap of the conductive phases (such as fibers, powders, and nanocarbon materials) in the concrete matrix are the basis for the formation of the conductive network. During the mixing and pouring process of the concrete, these conductive phases will be randomly distributed in the matrix. As the matrix hardens and takes shape, direct contact, partial overlap, and interweaving will occur between them, forming a three-dimensional network structure that can conduct electrons. In this network, the contact points between the steel fibers provide paths for electron conduction.

[0042] In the embodiments of the present invention, the charge carriers involved in the conductive network include ions, electrons, and holes. Among them, ions are associated with free pore water, and electrons and holes are closely related to fibers and nanocarbon respectively. The fibers will be intertwined in the concrete, and the nanocarbon materials will adhere to the surface of the fibers or fill the pores in the matrix, forming a close contact with the fibers, thereby promoting the conduction of electrons and holes.

[0043] In the embodiments of the present invention, a comprehensive method of electrode arrangement, applied external electric field, and combined with Ohm's law is used to measure the resistance. The obtained resistance test values cover both direct current and alternating current parts, so as to comprehensively reflect the electrical characteristics of self-sensing UHPC.

[0044] In the embodiments of the present invention, the resistance value of the self-sensing UHPC is mainly restricted by the influence of matrix deformation (including elastic and plastic deformation) and cracking / damage conditions on the conductive network during the application of tensile and compressive stresses. Currently, only two stress forms, namely tension and compression, are considered. Among them, during the tensile process, the resistance value of the self-sensing UHPC increases with the increase of tensile strain. During the compression process, the resistance value of the self-sensing UHPC shows a monotonically decreasing trend before reaching compressive failure. Based on these characteristics, the stress state of the UHPC can be determined according to the resistance-stress / strain response, and its characteristics are as Figure 9 shown.

[0045] In the embodiments of the present invention, the design of the intelligent sensing FRP corrugated pipe integrates advanced sensing technologies, aiming to achieve all-round and accurate real-time sensing of the environment where the corrugated pipe is located, thereby ensuring the safe and stable operation of related structures. A variety of intelligent components are integrated inside the intelligent sensing FRP corrugated pipe, including optical fibers, pressure sensors, resistance sensors, etc. During the operation of these sensors, various monitored physical quantities are converted into electrical signals or optical signals in real time. Subsequently, through wired or wireless transmission methods, these signals are stably transmitted to the monitoring system. In the monitoring system, professional signal processing algorithms and data analysis technologies are used to deeply analyze the received signals. By comparing with preset thresholds and models, the system can accurately judge key information such as the stress distribution, deformation degree, temperature change trend of the corrugated pipe, and whether damage occurs. Once an abnormal situation is detected, the system will immediately trigger an early warning mechanism and notify relevant personnel to take measures in a timely manner, thereby effectively realizing the functions of intelligent monitoring and early warning, and strongly ensuring the safety and reliability of the structure during the entire service life. The working process and principle schematic diagram can be referred to Figure 10 .

Claims

1. A semi-assembled composite column for intelligent monitoring, characterized in that: It includes a smart UHPC-FRP corrugated pipe prefabricated formwork and a core concrete column cast inside the smart UHPC-FRP corrugated pipe prefabricated formwork; the smart UHPC-FRP corrugated pipe prefabricated formwork is prefabricated in a factory, the smart UHPC-FRP corrugated pipe prefabricated formwork includes a self-sensing UHPC pipe and a smart sensing FRP corrugated pipe, the self-sensing UHPC pipe is cast into one with the smart sensing FRP corrugated pipe using the smart sensing FRP corrugated pipe as an inner template, and the self-sensing UHPC pipe is used to improve the smart sensing FRP corrugated pipe and The durability of the internal core concrete column, the high strength of the self-sensing UHPC pipe and the high restraint capacity of the smart sensing FRP corrugated pipe are combined to improve the ability of the core concrete column to resist lateral deformation; the self-sensing UHPC pipe has a self-sensing function, which is used to monitor the internal structural health information of the UHPC pipe in real time to achieve intelligent monitoring and maintenance; the smart sensing FRP corrugated pipe is used as the inner wall material of the formwork to monitor the health information between the smart UHPC-FRP corrugated pipe prefabricated formwork and the internal core column in real time, providing data support for structural health monitoring.

2. The semi-assembled composite column for intelligent monitoring according to claim 1 is characterized in that: The health information of the internal structure of the UHPC pipe includes stress changes; the health information between the prefabricated shell and the internal core column of the smart UHPC-FRP corrugated pipe includes stress and strain changes.

3. The semi-assembled composite column for intelligent monitoring according to claim 1 is characterized in that: The intelligent UHPC-FRP corrugated pipe prefabricated formwork comprises at least two segments, and adjacent segments are connected by FRP pipe socket joints, threaded joints embedded in the UHPC pipe, and grouting wet connections.

4. The semi-assembled composite column for intelligent monitoring according to claim 3 is characterized in that: The intelligent UHPC-FRP corrugated pipe prefabricated formwork comprises an upper bell end and a lower spigot end, the FRP corrugated pipe at the upper bell end is flush with the self-sensing UHPC pipe, and the FRP corrugated pipe at the lower spigot end protrudes 15 to 30 cm from the self-sensing UHPC pipe.

5. The semi-assembled composite column for intelligent monitoring according to claim 3 is characterized in that: The self-sensing UHPC pipe at the socket end of the intelligent UHPC-FRP corrugated pipe prefabricated template is pre-buried with a stainless steel threaded pipe groove, and a grouting sealing groove and a grouting hole are reserved, and the grouting hole and the grouting sealing groove are communicated; the self-sensing UHPC pipe at the socket end of the UHPC-FRP corrugated pipe prefabricated formwork is pre-buried with a stainless steel threaded pipe plug, the stainless steel threaded pipe plug protrudes 15 to 30 cm from the self-sensing UHPC pipe, and a slurry outlet hole and a splicing gap are reserved, and the slurry outlet hole and the splicing gap are communicated.

6. The semi-assembled composite column for intelligent monitoring according to any one of claims 1 to 5, characterized in that: The self-sensing UHPC tube is provided with self-sensing functional materials, which include conductive fibers. The diameter of the conductive fibers is between 0.2 and 0.5 mm, the length is between 5 and 30 mm, and the volume fraction of the conductive fibers is between 1.0% and 3.0%. The conductive fibers are in contact with each other, partially overlapped and interwoven in the UHPC tube to form a three-dimensional network structure that can conduct electrons. The conductive fibers are any one of conductive carbon nanotubes, steel fibers, carbon fibers, graphene, polypyrrole, and polyaniline. The self-sensing functional materials also include functional materials, and the volume fraction of the functional materials is between 0.1% and 1.0%.

7. The semi-assembled composite column for intelligent monitoring according to any one of claims 1 to 5, characterized in that: The intelligent sensing FRP bellows senses the influence of the mold shell constraint load through the built-in sensor and transmits the information to the monitoring system to realize intelligent maintenance.

8. The semi-assembled composite column for intelligent monitoring according to claim 7 is characterized in that: The sensor is an optical fiber sensor, a resistance sensor or a strain sensor.

9. The method for constructing a semi-assembled composite column according to any one of claims 1 to 8, characterized in that: include: Using the intelligent sensing FRP corrugated pipe as an inner template to cast a self-sensing UHPC pipe to form an intelligent UHPC-FRP corrugated pipe prefabricated shell; The intelligent UHPC-FRP corrugated pipe prefabricated formwork is used as the template to cast the core concrete column.

10. The construction method according to claim 9, characterized in that: The intelligent UHPC-FRP corrugated pipe prefabricated shell consists of at least two segments connected by wet method, and the connection method is: The FRP threaded pipe at the spigot end of the upper pipe section is inserted into the FRP threaded pipe at the socket end of the lower pipe section; the stainless steel threaded plug embedded in the UHPC pipe at the spigot end of the upper pipe section is inserted into the stainless steel threaded pipe groove reserved in the UHPC pipe at the socket end of the lower pipe section, and tightened along the thread; grouting is carried out from the grouting hole into the grouting sealing groove until slurry is seen coming out of the grouting hole, indicating sufficient grouting. The grouting material used is high-strength non-shrinkage grouting material.

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